*3.3. Hydrolysate Sterilization*

Sterilization is an important step to be performed when a pure culture has to be used in a bioprocess. However, since sterilization conditions can a ffect the composition of the hydrolysate, three di fferent methods were evaluated in this study with the aim of selecting the option that most favors the production of itaconic acid by fermentation. Sugar degradation with consequent formation of toxic compounds (5-HMF and furfural) and carbon-to-nitrogen ratio (C:N ratio) were the responses considered to select the best sterilization method.

Although the temperatures used for autoclaving could promote some degradation of glucose and xylose into 5-HMF and furfural, respectively, the formation of these compounds was low for all three sterilization methods evaluated (Figure 1). For the membrane sterilization, the 5-HMF obtained was mostly likely residual and was already present after the enzymatic hydrolysis. It is well known that 5-HMF and furfural are toxic compounds that can affect the microbial performance during fermentation [21]. In the case of itaconic acid production, 5-HMF and furfural concentrations of 0.4 g/L have been reported as being toxic for *A. terreus*, inhibiting the growth, sugar utilization, and product formation [22]. These values are much higher than the concentrations found in the cellulose pulp hydrolysate, independent of the sterilization method applied (Figure 1). Therefore, it can be concluded that none of the sterilization methods was able to promote significant degradation of sugars and formation of toxic compounds at a level unsuitable for fermentation.

**Figure 1.** Concentration of 5-HMF and furfural in the cellulose pulp hydrolysate after sterilization by three different methods.

The carbon-to-nitrogen ratio (C:N ratio) is another important characteristic of the hydrolysate that can strongly affect the microbial performance during fermentation, being of high importance to define a suitable C:N ratio to obtain high product yield during fermentation [23]. Analyses of the carbon and nitrogen contents in the cellulose pulp hydrolysate revealed that the carbon composition was not affected by any of the sterilization methods evaluated in this study. However, the nitrogen content was changed, leading to hydrolysates with different C:N ratios (Table 3). Sterilization by filtration clearly resulted in a medium with lower content of nitrogen, which was also visually cleaner and more translucent than the hydrolysates sterilized by autoclaving (figure not shown). According to the literature, nitrogen limitation can be beneficial for the production of organic acid [18]. Since nitrogen is required for biomass production, lack of nitrogen can slow down cell growth, to which some fungi respond by increasing the organic acid production [18]. In addition, high C:N ratios would direct more carbon into the tricarboxylic acid (TCA) cycle, allowing for higher productivities [24]. Ratios that are too high, however, could lead to reduced productivity due to substrate inhibition [18].

**Table 3.** Carbon and nitrogen contents in the hydrolysate after sterilization by different methods.

In order to select the sterilization method more suitable for the production of itaconic acid by *A. terreus*, fermentation assays were performed using the sterilized hydrolysates, with and without nutrient supplementation. No biomass growth or glucose consumption were observed from media without nutrient addition, thus, confirming the necessity of adding nutrients to all the hydrolysates. The results obtained from fermentation of sterilized hydrolysates with nutrient supplementation showed a clear advantage for the method of sterilization by membrane filtration (Figure 2), which provided

the highest itaconic acid yield (0.52 g/g) and productivity (0.40 g/L·h) after 72 h (Table 4). It is also interesting to note that glucose consumption and itaconic acid production were maximum at 72 h of fermentation but decreased afterwards, indicating possible consumption of the product when glucose, the main carbon source, was exhausted.

**Figure 2.** Glucose (solid lines) and itaconic acid (dashed lines) concentrations during the fermentation of the cellulose pulp hydrolysate sterilized by different methods. Membrane filter 0.2 μm (-); autoclave at 112 ◦C (•); and autoclave at 121 ◦C (). All the hydrolysates were supplemented with nutrients to be used as fermentation medium.

Analysis of the fermentation parameters (Table 4) clearly indicated that the hydrolysate sterilized by the filtration method promoted the best fermentation performance, resulting in the highest values of itaconic acid yield (*YP*/*S*) and productivity (*QP*). Such a result could be attributed to the C:N ratio present in the hydrolysate. The filtration method resulted in lower nitrogen content in the hydrolysate, and, as a consequence, in a higher C:N ratio that could have changed the metabolism towards acid production as opposed to fungal growth, thus, explaining the highest production of itaconic acid and the lowest production of biomass obtained from this medium. It is also worth noting that the production of itaconic acid from cellulose pulp hydrolysate sterilized by membrane filtration obtained in the present study compares very well to other studies on the production of this acid from different biomass hydrolysates [25,26]. When corn starch and wheat bran hydrolysates were used as fermentation medium for *A. terreus*, itaconic acid yields of 0.41–0.42 (g/g) were obtained [26].

**Table 4.** Fermentation parameters obtained for the production of itaconic acid by *A. terreus* from cellulose pulp hydrolysate sterilized by different methods.

*YP*/*S*, itaconic acid yield per sugar consumed; *YX*/*S*, biomass yield per sugar consumed; and *QP*, itaconic acid productivity.

On the basis of the above, sterilization by membrane filtration was selected as the most suitable sterilization technique as it provided the best results of itaconic acid titer, yield and productivity, and therefore was the sterilization method used in all the subsequent experiments.

### *3.4. E*ff*ect of Aeration on the Production of Itaconic Acid*

A sufficient oxygen supply is a fundamental requirement for a successful performance of the microbial strain during fermentation processes. To better understand its effect on the fermentation of cellulose pulp hydrolysate by *A. terreus*, three different aeration conditions were tested in a shake flask setup (Table 1), which were promoted by varying the working volume used in the flasks. A similar setup has been used and discussed in other studies to understand the effect of aeration during fermentation in flasks [27,28]. Results of these experiments are summarized in Table 5**.**

**Table 5.** Fermentation parameters obtained during the production of itaconic acid by *A. terreus* from cellulose pulp hydrolysate under different aeration conditions.

*YP*/*S*, itaconic acid yield per sugar consumed; *YX*/*S*, biomass yield per sugar consumed; and *QP*, itaconic acid productivity.

Interestingly, the two boundary conditions, Vair/Vm of 11.5 and 4, showed a decreased fermentation performance as compared with that observed for the intermediate condition, Vair/Vm of 7.33 (Table 5). In addition, the biomass yield was lower for a Vair/Vm of 7.33, revealing that an increased flux of carbon was deviated to the product formation under this oxygen condition. These results indicate that oxygen plays an important role in the production of itaconic acid by *A. terreus* from cellulose pulp hydrolysate. Therefore, selecting the ideal condition is highly important to maximize the product formation since conditions of excess or limitation of oxygen did not provide the best results. According to some authors, interrupting aeration can completely stop the production of itaconic acid by *A. terreus* [29]. Moreover, experiments using different shaking speeds in flasks showed that lowering the RPMs had a negative effect on the production of itaconic acid [22]. On the other hand, research with *Aspergillus niger* revealed that a reduced level of dissolved oxygen has a positive effect on the production of itaconic acid since high levels of dissolved oxygen increase the production of other organic acids such as citric and oxalic acid, which redirects carbon away from itaconic acid production [30]. Therefore, it is important to manage the aeration of the system carefully according to the strain and medium conditions used. Low and high concentrations of dissolved oxygen could both have an adverse effect on the production of itaconic acid. Research is, therefore, required to establish the best oxygen level to be used during fermentation. This is also of great importance for upscaling experiments in bioreactors.

Since a Vair/Vm of 7.33 was the oxygen condition that provided the best results of itaconic acid production, this condition was selected and used in the subsequent experiments.

### *3.5. E*ff*ect of C:N Ratio on the Production of Itaconic Acid*

Considering that the previous experiments on the sterilization method suggested a significant influence of the C:N ratio on the production of itaconic acid, additional experiments were performed at this step to explore such effect with the aim of selecting conditions able to improve the production of itaconic acid from cellulose pulp hydrolysate. As a first approach, experiments consisted in changing the nitrogen availability in the medium by varying the concentration of (NH4)2SO4 added to it. As can be seen in Table 6, the addition of 1 g/L (NH4)2SO4 did not provide sufficient nitrogen for the microorganism to properly metabolize the carbon source and convert it into itaconic acid. Better results were obtained for the other two nitrogen concentrations tested, 3 and 5 g/L. From these, supplementation of the medium with 3 g/L (NH4)2SO4 gave the best results of itaconic acid production, with yield and productivity of 0.52 g/g and 0.40 g/L·h, respectively. These results confirm that the production of itaconic acid can be improved by using an appropriate C:N ratio. Nitrogen limitation or excess are both non ideal conditions for the metabolism of *A. terreus* go through the itaconic acid formation.

The influence of different nitrogen sources and concentrations on the production of itaconic acid has also been reported in other studies using different microbial strains and fermentation media. For example, the production of itaconic acid by the fungus *Ustilago maydis* in medium containing 200 g/L of glucose was improved when the concentration of NH4Cl added as nitrogen source was

increased from 15 to 75 mM [31]; while the production of itaconic acid by *A. terreus* ATCC 10020 from rice husk hydrolysate containing 15 g/L of glucose was improved when the medium was supplemented with 1.3 g/L NaNO3 and 1.1 g/L (NH4)2SO4 [12]. This makes it possible to conclude that different strains have different nitrogen requirements for their metabolism and, according to the medium used for fermentation, different concentrations of nitrogen should be added to promote the best performance of the strain towards product formation.

**Table 6.** Effect of the nitrogen concentration on the fermentation parameters obtained during the production of itaconic acid by *A. terreus* from cellulose pulp hydrolysate.

*YP*/*S*, itaconic acid yield per sugar consumed; *YX*/*S*, biomass yield per sugar consumed; and *QP*, itaconic acid productivity.

As a second approach to explore the effect of the C:N ratio on the performance of *A. terreus* to produce itaconic acid from cellulose pulp hydrolysate, small changes in the carbon composition were made for a fixed medium supplementation of 3 g/L (NH4)2SO4 (which gave the best results of itaconic acid production in the previous experiments). According to the results, when the initial concentration of glucose in the medium was increased from 45 to 60 g/L, a significant increase in the production of itaconic acid could be observed, which resulted in 2.3 times and 3 times higher values of yield and productivity, respectively (Table 7). These results reinforce that increasing the initial concentration of carbon source is an important strategy to result in a higher production of itaconic acid by *A. terreus*. However, within the scope of this study, higher concentrations of initial glucose were not evaluated since, as the nitrogen supplementation was fixed, increased carbon sources would lead to much higher C:N ratios, which could negatively impact on the production of itaconic acid. For future experiments, higher concentrations of glucose should be tested using an appropriate nitrogen supplementation to offer the ideal C:N balance required by the strain to maximize the formation of itaconic acid from cellulose pulp hydrolysate.

**Table 7.** Effect of the substrate concentration on the fermentation parameters obtained during the production of itaconic acid by *A. terreus* from cellulose pulp hydrolysate.

*YP*/*S*, itaconic acid yield per sugar consumed; *YX*/*S*, biomass yield per sugar consumed; and *QP*, itaconic acid productivity.

Finally, considering the different strategies evaluated in the present study, sterilization of the cellulose pulp hydrolysate by membrane filtration, medium supplementation with 3 g/L (NH4)2SO4, 60 g/L of initial glucose concentration, and oxygen availability of 7.33 (volume of air/volume of medium) were the most suitable to maximize the production of itaconic acid by *A. terreus*, resulting in a production of 37.5 g/L, corresponding to a yield of 0.62 g/g glucose consumed, and productivity of 0.52 g/L·h. These values compare very well to other recent studies on the production of itaconic acid by *A. terreus* from different lignocellulosic feedstocks (Table 8) and confirm the feasibility of using bleached cellulose pulp for this application. These results can still be improved by optimization of the fermentation conditions using a bioreactor setup, which will be investigated in a next study.

**Table 8.** Production of itaconic acid by *A. terreus* from different lignocellulosic feedstocks. All the values correspond to experiments in flasks.


**4.2. Inclusion on the waiting list**

**4. Waiting list for pancreas transplantation**

266 Organ Donation and Transplantation - Current Status and Future Challenges

living kidney donor and a preemptive kidney transplant.

Evaluation of the candidates for pancreas transplantation should be performed as early as possible, in order to identify those who would benefit the most from the procedure. In patients with chronic kidney disease, we recommend referral to a pancreas transplant center as soon as glomerular filtration rate (GFR) falls below 25–30 ml/min. This early referral offers precious time for patient evaluation and possible inclusion on the waiting-list pre-dialysis. Additionally, and depending on transplant center policies, this allows the study of a possible

Patient evaluation and clinical workup is similar to that performed for kidney transplantation, such as complete medical history, immunological study, uremic state, liver disease, cancer and infection screening, with some additional particularities related to diabetic disease: hormonal study, β cell autoantibodies, as well as study of the main diabetic complications.

• Hormonal assessment: the main purpose is to determine whether or not the patient has endogenous insulin secretion. For this, it is sufficient to determine the fasting plasma levels

• Autoantibodies: the main objective of pre-transplant quantification of β cell autoantibodies (IAA, GAD, ZnT8A, IA2) is to establish a baseline. These tend to be negative after years of evolution of DM, and therefore negative at the time of transplantation. Their presence does not represent a contraindication for pancreas transplantation. During follow-up, nonethe-

• Diabetic retinopathy is present in up to 90% of of all transplant candidates, with varying

• Diabetic polyneuropathy is also present in majority of patients but rarely contraindicates the transplant. However, it is advisable to take into account the severe dysfunction of the autonomic nervous system, due to post-transplant complications and the negative impact on patient survival. Diabetic neuropathy can often affect the urinary bladder leading to incontinence or incomplete bladder emptying. If urinary exocrine drainage is used, a urinary urethrocystography is recommended to rule out pathology of the bladder and urethra, as

• Cardiovascular evaluation is the most important due to the impact of cardiovascular disease on post-transplant mortality and morbidity. Previous history of myocardial infarction, angioplasty, or coronary bypass should not necessarily be a contraindication to transplantation. Workup should be exhaustive before including the patient on the waiting list. It is advisable to perform an electrocardiogram (EKG) and a pharmacological stress test with MIBI-dipyridamole, as well as an echocardiography to evaluate ventricular ejection fraction and exclude motility disorders. If any of these tests are pathological, coronary angiography should be performed to identify more accurately the existing lesions and

of C-Peptide. Its negativity indicates the absence of insulin secretion.

well as a cystomanometry to study and evaluate bladder function.

less, its reappearance is associated with an increased risk for disease relapse.

degrees of severity. It is not considered an exclusion criteria for transplantation.

**4.1. Evaluation of candidates**

At the time of inclusion on the waiting list, a checklist should be performed to ensure all pretransplant studies have been completed, and revised by the medical team. It is important to ensure that the patient has received a clear and comprehensible information regarding the advantages, as well as of the possible complications of the transplant, so that he can decide to freely choose this form of treatment.

Logistical issues should also be discussed in advance with the patient, in order to minimize the time from patient contact to the surgical procedure (hence cold ischemia time). The patient and his closest relatives should be aware of the expected duration of the intervention, median hospital stay, and most important post-transplant cares and outpatient visits.

Also, and for as long as they remain on the waiting list, the patient should be made aware of the importance of maintaining regular communication with the transplant center. The high incidence of complications that may occur in these diabetic patients, especially if they are affected by chronic renal failure and are also waiting for a simultaneous kidney transplant, requires strict monitoring and follow-up as long as they are not transplanted. Ideally, they should be visited by a member or collaborating doctor of the transplant team every 3–4 months. Only in this way, it is possible to detect possible events that may represent a temporary contraindication for the intervention.


*5.2.2 Gingivectomy by laser*

Soft tissue lasers are used for treatment of gingival enlargement. Commonly used lasers are carbon dioxide (CO2) and the neodymium:yttrium-aluminum-garnet (Nd:YAG), which have wavelengths of 10,600 and 1064 nm, respectively. Proper protection should be observed along with eyewear and avoidance of any reflective surfaces. The procedure is similar to that of electrosurgery. Laser tip is used instead

**Figure 17.** *Gingivectomy by electrosurgery: preoperative view.*

#### **Figure 18.** *Gingivectomy by electrosurgery: incision with electrode tip.*

**Figure 19.** *Gingivectomy by electrosurgery: postoperative view after 1 month.*

of electrodes for cutting and coagulation. Compared with the use of a conventional scalpel, lasers can cut, ablate and reshape the oral soft tissue more easily, with no or minimal bleeding and little pain as well as no or only a few sutures. Laser surgery occasionally requires no local anesthetic, or only a topical anesthetic [40].


**2. Theoretical framework**

The theoretical framework underpinning this chapter is Afrocentric-centered leadership in the context of higher education. Higher education leadership has a mammoth task of not only transforming these giant intellectual institutions but to also ensuring that the core business of teaching, research, and community engagement are pursued ethically and professionally [22]. Afrocentrism leadership demonstrates that like Western and Oriental cultures, Africans have ideas, norms, traditions, culture, and values that shape their worldview [25]. The Afrocentriccentered leadership is built upon the theory of Afrocentrism, which points to the fundamental African leadership framework. The central supremacy of African culture and knowledge in addressing African development challenges is the main thrust of Afrocentric leadership [26]. Afrocentric-centered leadership is a scientific approach to African development that is founded on African history, culture, behavioral patterns, beliefs, and norms. It is not a carbon copy of Western leadership models [27]. Afrocentric leadership is, therefore, an African-centered approach on indigenous African cultures in order to harvest a variety of leadership principles, patterns, practices, institutions, ceremonies, and ideas for modern use [28]. As this leadership is founded on Afrocentrism, it is a direct reaction to Eurocentrism, a cultural phenomenon that elevates European cultural values above those of other cultures and universalizes European, and thus American, experiences for other cultures around the world. According to Afrocentric-centered leadership, Fairfax [29] alludes that Western leadership and development ideologies are based on European culture and norms. Because African experiences differ greatly from those of America or Europe, Afrocentric-centered leadership contends that applying Western theories to explain African people's ethos is inappropriate and should be deconstructed [25].

Within an educational context, Afrocentric-centered leadership strives to achieve the overarching Afrocentric theory's goal of African-led and African-centered development. Focusing and involving critical components such as indigenous knowledge systems, African philosophies and experiences remain relevant to leadership [30]. The foundation of Afrocentric-centered leadership is based on African lived experiences, regional economic and social requirements, African values and traditions [31]. These are applied as a means of understanding diverse disciplines and carving out a place for oneself in the world. Through such use of Afrocentric-centered leadership education, Africans discover their roots, fall in love with their content, and assume responsibility for it. They possess a "decolonized agency," as described by Abdi [30], which enables them to challenge unassuming but racist and foreign structures of knowledge that influence everyday contact. As a result, Afrocentric leadership promotes an African worldview that is inclined toward their psychic and cultural independence, which Afrocentrism claims is essential to Africa's growth [32]. In essence, higher education leadership foregrounded on Afrocentricity has the potential to enhance scholarship that reaffirms African intellectualism and capabilities [33]. Furthermore, Sabela ([33], p. 29) argues that discourse on Afrocentrism could be instrumental in addressing issues of "inclusivity, to redress the past deficiencies of equity access and outcomes, reduce socio-economic inequality, and stimulate physical wellbeing." For higher education to deal with the besetting challenges, transformational leadership is imperative, transformative leadership can be applied to foster collaboration among African universities in core functions of research and innovation [34]. This could include areas to build institutional capacity, exchange programs and infrastructure for effective interventions in dealing with African problems. In this regard, Marwala [35] opines that there is a need for Africa to transform the higher education system in its quest to build world-class universities. For Marwala [35], this mammoth task could be actualized by: a) reforming the curriculum for relevance, b) improving infrastructure inclusive of the 4IR infrastructure, c) increasing research capacity through postdoctoral research fellowships, visiting academics, research centers and institutes, e) galvanizing funding for human and technological readiness. Above these pointers, universities can be accessible to citizens and for public good.

*Toward Advancing African Scholarship through Afrocentric Leadership in Higher Education DOI: http://dx.doi.org/10.5772/intechopen.108459*

Afrocentric-centered leadership is geared toward breaking free from colonial and post-colonial thinking and recommit to an African value system, leading to calls for an "African Renaissance" inside the continent itself in recent years [27, 36–38]. These concepts have gained traction across the continent and have since been used to lead businesses and communities. Therefore, aspects of "Western culture with its narrow, arrogant, empty, materialistic values of hamburger and cocaine" [39–42] must be rejected in order for this shift to a more Afro-centric leadership views to take place. A reconnection with African "indigenous knowledge" that places an emphasis on interdependence and solidarity is required. However, given the hybridity argument, such an aspiration is intriguing and poses important issues regarding (a) how this Afro-centric knowledge can be (re)discovered, (b) how it can be captured and transmitted, and (c) the degree to which it will resonate with the lived experience of modern Africans on the continent and elsewhere [27, 41].


**2.5.3 Brain**

Despite the fact that iodine is one of the most important essential elements, the quantitative data on its concentration in the human brain is really scarce. The nature and site of iodine binding in the human brain is still unknown. The results of Andrasi et al. (Andrási et al., 2004) investigations on iodine distribution between the lipid fraction and in the brain tissue without lipid have indicated that its mean contents vary between 910 ± 147 ng/g dry weight and 281 ± 68 ng/g dry weight depending on the brain region (the highest content was found in susbstantia nigra and the lowest in vermis crebelli).


**3. Assessment of phytoextraction**

#### **3.1. Advantages of phytoextraction**

had an average BLL of 60 μg/dL [16, 17]. Additionally, the soil near a car battery processing workshop in Kerman City, Iran, was found to contain 5, 780 mg/kg of lead [18]. The BLL of Indians near a residential area was 20–25 μg/dL, and the lead concentration of PM10 (or PM2.5)

Soil pollution from lead was not observed in the major cities in China, such as Beijing and Hong Kong; therefore, the BLLs of inhabitants in these cities were normal (4–5 μg/dL) [20-22]. The number of mining and metallurgy factories is rapidly increasing in China due to the increased consumption of lead-acid batteries. However, no formal reports on the lead con‐ centration and BLL have been reported in areas predominantly inhabited by mining and metallurgy factories, such as Zhejiang and Guangdong provinces. According to the WEB report [4], it is suspected that 100, 000 children are suffering due to lead toxicity. Therefore, in China, the areas predominantly inhabited by mining and/or metallurgy industries are thought to contain extremely high lead concentrations which are exhausted into the air, river, and soil. Another potential cause of soil pollution from lead is a firing range. One of the worst cases of soil pollution from lead at a firing range demonstrated more than 10 kg/kg of lead due to remnant lead alloy bullets. Therefore, lead pollution in firing ranges may be as harmful as in

**2.4. Effects of lead pollution on the health of inhabitants living near metallurgy and mining**

The BLL is an indicator of pollution from lead. Lead decreases the IQ value when the BLL is greater than 20 μg/dL [23]. A test to measure the ability of recognition in monkeys suggested that dysgnosia was observed in monkeys with BLLs of 10–13 μg/dL. Moreover, lead toxicity was observed when the BLL exceeded 40 μg/dL. According to recent studies, the BLL should

The main route of exposure for an elevated BLL is ingestion. The amount of lead that adult subjects ingest from food is generally 20–25 μg/kg and 5–10 % is absorbed. Approximately 100 mg of lead is present in the body. The sensitivity of lead in a child is much higher than in an adult because 40 % of the ingested lead is absorbed. A previous report demonstrated that when more than 5 μg/kg/day of lead was ingested in infants, 32 % of the lead was absorbed, although no accumulation was observed in infants who ingested less than 4 μg/kg/day. The WHO also suggested that the BLL was not increased in those who ingested less than 4 μg/kg/day [26]. The other most common route of exposure is polluted air. Approximately 40–50 % of lead taken in from the nose is absorbed by the lung. The relationship between the concentration of lead in the air and the BLL is shown in Figure 3 (based on the data from the study by Thomas et al. on pollution from lead gasoline [11]). The BLL was found to be strongly correlated with air

Safety standards are defined to keep the environment safe. In Japan, the lead concentrations

BLL observed in Japanese is 1–3 μg/dL, and the normal concentration of lead in the soil is 15– 30 mg/g. The lead concentrations in the areas near mining and metallurgy industries listed in

and 0.01 mg/L, respectively. Moreover, the normal

) [11, 19].

in the residential area was very high (10–14 mg/m3

252 Advances in Bioremediation of Wastewater and Polluted Soil

mining areas.

be maintained below 10 μg/dL [24, 25].

in the air and wastewater are below 1 ng/m3

**areas**

pollution.

The remediation of polluted soil is extremely costly. In the United States, ten billion dollars were invested to remediate soil pollution in the 1990s. According to an approximate calculation of the cost [27], more than 100 billion dollars would be necessary for remediation of polluted soil in the 2000s; thus, an inexpensive process was sought to decrease the investment. Phy‐ toextraction is a remarkable process where heavy metals can be absorbed from the soil and accumulated into plants at high concentrations without the use of expensive equipment. The advantages of phytoextraction also include increased safety and inexpensive running cost compared to physical and chemical methods, such as washing and solidification. Phytoreme‐ diation is an expanding market; in the United States and Japan, it is expected to result in 170 million dollars and 800 million yen, respectively.

The plants which contain the highest abilities of absorption are called "hyperaccumulators" and are the most suitable for the phytoextraction of heavy metals. With regard to lead, a hyperaccumulator is defined as a plant that is capable of accumulating greater than 1, 000 mg/ kg dry biomass (or 100 times more than other plants) and generally shows a high tolerance to heavy metals. Some prominent hyperaccumulators have been screened and identified [28]. *Stanleya pinnata*, for example, was found to accumulate 3, 000 ppm of selenium in its leaves when planted on soil containing 6 ppm of selenium [29]. *Rinorea niccolifera* was recently found in Western Luzon, Philippines, and could accumulate an unusually high amount (18, 000 ppm) of nickel by detoxifying with vacuoles [30]. *R. niccolifera* was the most prominent hyperaccu‐ mulator, because it was capable of absorbing heavy metals at a value several hundred times higher than other plants.

Additionally, an interesting tree was found in the Sabah Parks in Malaysia. The green sap of the tree contained high concentrations of nickel [31, 32] and could be continuously collected. When the tree was planted in soil containing wastes from nearby mines, a green nickel-rich sap containing 20 % nickel was collected from the trees. The ash of the burned sap additionally contained high concentrations of nickel (10–25 %), which corresponded to 200 kg/ha (2, 000 dollars/ton). Those studies suggest that phytoextraction may be applicable to soil pollution from nickel.

#### **3.2. Phytoextraction of lead by a hyperaccumulator**

Hyperaccumulators absorbing lead have been screened as well as hyperaccumulators for other heavy metals. The chief hyperaccumulators introduced in this section are shown in Table 1. *Thlaspi caerulescens* [33], kenaf [34], sunflower [35], *Cannabis sativa* [36, 37], *Tagetes minuta* L. [38], cabbage [39], *Brassica juncea* [40], *Acacia victoriae* [41], and buckwheat are superior hyperaccumulators compared to other weeds and crops, and the following plants are espe‐ cially remarkable. *A. victoriae* was found to be capable of accumulating 3, 580 mg/kg of lead from a 1, 000 mg/L solution of lead nitrate. *B. juncea* additionally showed a high lead tolerance and could accumulate a significantly high concentration of lead (34, 500 mg/kg). Furthermore, Shinshu buckwheat, an improved breed developed by Shinshu University, was capable of growing in soil containing more than 3, 000 mg/kg of lead and could accumulate 6, 000–10, 000 mg/kg of lead. Buckwheat may be the most suitable plant because it is obtained at a high yield (700 g/ha/year) [42].

Additionally, two types of pteridophytes, *Athyrium yokoscense* and *Pteris vittata*, showed high tolerance to lead. *A. yokoscense* is typically found around mine areas containing high concen‐ trations of heavy metals. It is known as an indicating plant to explore gold veins in Japan, as it lives in a cluster around areas of gold rubbish. One gametophyte of *A. yokoscense* was capable of accumulating high concentrations of lead (10, 000 mg/kg) and showed tolerance to extremely high concentrations of lead [43]. *P. vittata* has been shown to accumulate arsenic. A breed belonging to *P. vittata* could accumulate 16, 257.5 mg/kg of lead and grow in soil containing 92, 900 mg/kg of lead. Additionally, it accumulated 4, 829 mg/kg of lead when it was grown in mine soil for six months [44].

The two types of mosses *Scopelophila cataractae* and *Funaria hygrometrica* were also identified as hyperaccumulators. *S. cataractae*, which is known as "copper moss" in Japan, was found in soil containing high concentrations of copper and could accumulate copper selectively at the cell wall. Moreover, a breed belonging to *S. cataractae* could accumulate lead as well as copper. *F. hygrometrica* additionally showed a very high ability of absorbing lead [45, 46]. The reports by Riken (Japan) suggested that *F. hygrometrica* adsorbed 70 % of lead per dry biomass when an effluent containing lead was supplied to the column containing the moss [47]. An advantage of using moss is that it can grow at a fast rate without water. Thus, mosses may be suitable for areas in which there is little water.

when planted on soil containing 6 ppm of selenium [29]. *Rinorea niccolifera* was recently found in Western Luzon, Philippines, and could accumulate an unusually high amount (18, 000 ppm) of nickel by detoxifying with vacuoles [30]. *R. niccolifera* was the most prominent hyperaccu‐ mulator, because it was capable of absorbing heavy metals at a value several hundred times

Additionally, an interesting tree was found in the Sabah Parks in Malaysia. The green sap of the tree contained high concentrations of nickel [31, 32] and could be continuously collected. When the tree was planted in soil containing wastes from nearby mines, a green nickel-rich sap containing 20 % nickel was collected from the trees. The ash of the burned sap additionally contained high concentrations of nickel (10–25 %), which corresponded to 200 kg/ha (2, 000 dollars/ton). Those studies suggest that phytoextraction may be applicable to soil pollution

Hyperaccumulators absorbing lead have been screened as well as hyperaccumulators for other heavy metals. The chief hyperaccumulators introduced in this section are shown in Table 1. *Thlaspi caerulescens* [33], kenaf [34], sunflower [35], *Cannabis sativa* [36, 37], *Tagetes minuta* L. [38], cabbage [39], *Brassica juncea* [40], *Acacia victoriae* [41], and buckwheat are superior hyperaccumulators compared to other weeds and crops, and the following plants are espe‐ cially remarkable. *A. victoriae* was found to be capable of accumulating 3, 580 mg/kg of lead from a 1, 000 mg/L solution of lead nitrate. *B. juncea* additionally showed a high lead tolerance and could accumulate a significantly high concentration of lead (34, 500 mg/kg). Furthermore, Shinshu buckwheat, an improved breed developed by Shinshu University, was capable of growing in soil containing more than 3, 000 mg/kg of lead and could accumulate 6, 000–10, 000 mg/kg of lead. Buckwheat may be the most suitable plant because it is obtained at a high yield

Additionally, two types of pteridophytes, *Athyrium yokoscense* and *Pteris vittata*, showed high tolerance to lead. *A. yokoscense* is typically found around mine areas containing high concen‐ trations of heavy metals. It is known as an indicating plant to explore gold veins in Japan, as it lives in a cluster around areas of gold rubbish. One gametophyte of *A. yokoscense* was capable of accumulating high concentrations of lead (10, 000 mg/kg) and showed tolerance to extremely high concentrations of lead [43]. *P. vittata* has been shown to accumulate arsenic. A breed belonging to *P. vittata* could accumulate 16, 257.5 mg/kg of lead and grow in soil containing 92, 900 mg/kg of lead. Additionally, it accumulated 4, 829 mg/kg of lead when it was grown

The two types of mosses *Scopelophila cataractae* and *Funaria hygrometrica* were also identified as hyperaccumulators. *S. cataractae*, which is known as "copper moss" in Japan, was found in soil containing high concentrations of copper and could accumulate copper selectively at the cell wall. Moreover, a breed belonging to *S. cataractae* could accumulate lead as well as copper. *F. hygrometrica* additionally showed a very high ability of absorbing lead [45, 46]. The reports by Riken (Japan) suggested that *F. hygrometrica* adsorbed 70 % of lead per dry biomass when an effluent containing lead was supplied to the column containing the moss [47]. An advantage

higher than other plants.

254 Advances in Bioremediation of Wastewater and Polluted Soil

**3.2. Phytoextraction of lead by a hyperaccumulator**

from nickel.

(700 g/ha/year) [42].

in mine soil for six months [44].

Ornamental plants adapted for phytoextraction were also screened. However, one such plant, *Chlorophytum comosum*, could only accumulate 516 mg/kg when 1, 250 mg/kg of lead was supplied in the soil [48]. The advantage of using ornamental plants is that the flowers may be reused after remediation [48, 49]. Moreover, ornamental plants do not show a high tolerance to lead. Therefore, they may be readily adapted for soil pollution in urban places because the lead concentrations in these areas are relatively low and the plants can be used in landscaping.

Trees have interesting characteristics for phytoextraction. The advantage of using a tree is that the root is much deeper, and therefore, it can be applied to the remediation of soil at a depth of 3–5 m. Conversely, the disadvantages are a slow growth rate and low tolerance to lead, although the biomass per land area is high. To overcome these disadvantages, the best trees were screened [50-52] and a combination of aspen and rowan trees [53], a combination of *Ixora coccinea* and *Ficus benjamina* [54], and the use of ornamental trees and timber trees [55] were examined to enhance the remediation efficiency. Additionally, a field trial experiment was performed [56, 57] and the tree showing the highest ability for phytoextraction was *Acacia mangium*, which is widely used in an artificial forest in Malaysia because it is capable of growing well even in nutrient-poor soil and shows a high ability to adapt to its environment. It is known that the forest is the first stage in maintaining air and soil safety by capturing lead in the leaves [58]. The best candidate tree will be one that can effectively transfer lead to its leaves or sap, because leaves and sap can be easily and continuously collected.

**Table 1.** Amounts of lead absorbed by important hyperaccumulators

#### **3.3. Enhancement of the efficiency of phytoextraction using ethylenediaminetetraacetic acid (EDTA)**

Lead readily converts to lead(II) oxide (PbO) through contact with oxygen in the air. The resultant PbO slowly converts to inorganic salts of lead, such as Pb(NO3)2, PbSO4, and PbCO3, by acid rain containing nitrate and sulfate ions or water saturating carbon dioxide (containing carbonate ions). Table 2 shows the solubility of inorganic salts of lead [59]. The solubility of PbSO4 and PbCO3 is very low. Inorganic salts and free lead ions are adsorbed on particles in the soil by forming a complex with organic compounds contained in the particles [60, 61] and gradually changed to more insoluble compounds by reacting with phosphate. Therefore, the concentration of free lead ions in the soil is extremely low. The rapid absorption by plants is disturbed due to the low concentration of free lead ions or its inorganic salts. The amount of free lead ions must be increased by removing lead salts adsorbed in the soil particles for rapid absorption.

Many methods to increase the efficiency of phytoextraction have been reported [62], and the best method was to supply ethylenediaminetetraacetic acid (EDTA) to the soil. The complex formation constants (pK) of EDTA to Pb(II), Cd(II), Zn(II), and Fe(III) are 18.3, 16.6, 16.7, and 24.2, respectively. Therefore, the lead ions of inorganic salts (or PbO) in the soil positively conform the complex followed by the addition of EDTA (pH < 7) [63]. In a pilot experiment, when the soil containing 1, 935 mg/kg of lead was washed with water containing EDTA, 97 % of lead was extracted from the soil [64, 65].

**Table 2.** Solubility of lead and its inorganic salts in water. This table is based on the WEB data [59]

Moreover, the processing time and accumulation in phytoextraction can be drastically shortened and enhanced by EDTA. For example, *Scirpus Maritimus* L. could adsorb 80 % of lead in the root within 60 days when 5 mmol/kg EDTA was supplied [66]. Absorbed amounts of lead in *Zea mays* L. and *Pisum sativum* L. were enhanced to 120 times [67], and Indian mustard *Brassica juncea* had increased absorption when EDTA was supplied [68]. Kos et al. [38] investigated the effect of 5 mmol/kg EDTA or 10 mmol/kg ethylenediamine-N, N'-disuccinic acid (EDDS) on lead accumulation in various plants, and the results suggest that *Cannabis sativa* contained the best phytoremediation potential (26.3 kg/ha) and accumulated 1, 053 mg/ kg of lead. Furthermore, for cabbage (a high-biomass crop), the accumulation and treatment period was enhanced (5, 010 mg/kg) and shortened, respectively, when 3.0 mmol/kg EDTA was supplied for seven days [40]. When buckwheat was cultivated in soil containing 13, 032 mg/kg of lead and EDTA and citric acid were supplied for two months, 22, 363 mg/kg of lead was accumulated in the shoots and leaves [69]. These results suggest that EDTA is effective for increasing the absorption of lead in plants.

However, there are several disadvantages for the use of EDTA. One is the low degrading characteristic of EDTA [70]. EDTA supplied in the soil exists without degradation for a long period of time and slowly degrades to diketopiperazines, which are toxic compounds. To solve this problem, EDDS, which has a higher biodegradability than EDTA, has been used [71-73], although the complex formation constants (pK) of EDDS are lower than that of EDTA and an unfavorable exchange between lead and the others often occurred [67, 68]. Another disadvant‐ age is the elution of other metal ions following the use of EDTA. The addition of EDTA in the soil causes the leakage of important minerals (e.g., Mg and Ca) necessary for the plant growth, and the effluent containing toxic ions (e.g., Pb, Hg, and As) pollutes the groundwater [74]. Therefore, EDTA or EDDS must be applied to the soil at the lowest effective concentrations.

#### **3.4. Improved procedure for the phytoextraction of lead**

by acid rain containing nitrate and sulfate ions or water saturating carbon dioxide (containing carbonate ions). Table 2 shows the solubility of inorganic salts of lead [59]. The solubility of PbSO4 and PbCO3 is very low. Inorganic salts and free lead ions are adsorbed on particles in the soil by forming a complex with organic compounds contained in the particles [60, 61] and gradually changed to more insoluble compounds by reacting with phosphate. Therefore, the concentration of free lead ions in the soil is extremely low. The rapid absorption by plants is disturbed due to the low concentration of free lead ions or its inorganic salts. The amount of free lead ions must be increased by removing lead salts adsorbed in the soil particles for rapid

Many methods to increase the efficiency of phytoextraction have been reported [62], and the best method was to supply ethylenediaminetetraacetic acid (EDTA) to the soil. The complex formation constants (pK) of EDTA to Pb(II), Cd(II), Zn(II), and Fe(III) are 18.3, 16.6, 16.7, and 24.2, respectively. Therefore, the lead ions of inorganic salts (or PbO) in the soil positively conform the complex followed by the addition of EDTA (pH < 7) [63]. In a pilot experiment, when the soil containing 1, 935 mg/kg of lead was washed with water containing EDTA, 97 %

**Compound Solubility to water**

Pb 3.1 x 10-5 PbO 5.04 x 10-3 (α form)

Pb3(PO4)2 1.4 x 10-5 PbHPO4 2.187 x 10-2 Pb(NO3)2 54.3 PbCO3 7.269 x 10-5 PbS 6.77 x 10-13 PbSO4 3.836 x 10-3 Pb(OH)2 1.615 x 10-3 Pb(CH3COO)2 44.3

Moreover, the processing time and accumulation in phytoextraction can be drastically shortened and enhanced by EDTA. For example, *Scirpus Maritimus* L. could adsorb 80 % of lead in the root within 60 days when 5 mmol/kg EDTA was supplied [66]. Absorbed amounts of lead in *Zea mays* L. and *Pisum sativum* L. were enhanced to 120 times [67], and Indian mustard *Brassica juncea* had increased absorption when EDTA was supplied [68]. Kos et al. [38] investigated the effect of 5 mmol/kg EDTA or 10 mmol/kg ethylenediamine-N, N'-disuccinic acid (EDDS) on lead accumulation in various plants, and the results suggest that *Cannabis sativa* contained the best phytoremediation potential (26.3 kg/ha) and accumulated 1, 053 mg/

**Table 2.** Solubility of lead and its inorganic salts in water. This table is based on the WEB data [59]

**g/100g H2O (20 °C)**

absorption.

of lead was extracted from the soil [64, 65].

256 Advances in Bioremediation of Wastewater and Polluted Soil

Two devises have been proposed to enhance the concentration of free lead ions or its inorganic salts. One is an electro-phytoextraction process. Electro-phytoextraction is performed under an electric field and can enhance the performance. For example, the absorption in ryegrass was enhanced when 1.0 V/cm of DC electrical field was given to the soil in a vertical direction [75], and the absorption in *Brassica juncea* was enhanced when an electric field was given at four times over 30 V [76]. Additionally, when 1.0 V/cm of AC electrical field, as well as DC, was given to rapeseed (*Brassica napus*) and tobacco (*Nicotiana tabacum*), the absorption of Cd and Pb in the shoots was enhanced [77].

Another device used to improve phytoextraction is the use of acid [78, 79]. The concentration of free lead is increased when the pH of the soil is more acidic (near pH 5). The solubility of lead phosphate, which is an insoluble compound, was enhanced by a 0.15 M citric acid solution [80], and oxalic acid was the best at enhancing the solubility of pyromorphite (Pb5(PO4)3Cl), an insoluble phosphate [81, 82]. Because microorganisms can secrete various acids, such as acetic, citric, and lactic acids, the soil pH may be decreased by supplements of these microor‐ ganisms. The effects of urea [83] and other chelate compounds [84, 85], as well as the effect of acids, were examined. The cells of *Rhizobacteria* could enhance the concentration of free lead by secreting siderophores [86] and aided in plant growth by secreting indoleacetic acid (IAA), a plant growth factor. Such microorganisms are referred to as "plant-growth-promoting rhizobacteria" (PERG) [87, 88].

#### **3.5. Transgenic approach to improve the phytoextraction of lead**

The improvement of a hyperaccumulator via gene manipulation is the most effective way to enhance its ability. Transgenic plants have been energetically developed since the 1990s [89-92]. Transgenic plants which could increase the volatility of heavy metals or decrease the toxicity of heavy metals may be the best candidates because the remediation process can be continuously carried out without removing the plants. Transgenic *B. juncea*, for example, expressing the cystathionine gamma-synthase gene of *Arabidopsis thaliana* L. could convert selenium to volatile dimethylselenium [93, 94], and a plant expressing the methylmercury lyase gene decreased the toxicity by reducing methylmercury to mercury [95]. However, vaporization is not acceptable for lead because methylated lead diffuses into the air and exhibits a high toxicity as previously described.

Thus, the following two mechanisms have been proposed. One method is to enhance the number of compounds capable of combining heavy metals, such as metallothionein, gluta‐ thione, and phytochelatin. For example, the absorption efficiency of transgenic *B. juncea* expressing adenosine triphosphate sulfurylase, glutamyl-cysteine synthetase, and glutathione synthetase genes was 4.3 times higher than that in the wild plant [96]. Moreover, the accumu‐ lation in *Nicotiana glauca* expressing phytochelatin synthase was also enhanced [97]. The other mechanism is to obtain a high lead tolerance by enhancing the transport into the cell and vascular membranes. Higher tolerance and accumulation of Zn, Mn, and Cd were realized by the plants transformed with a zinc transporter (*ZAT* or *AtMTP1*), *ShMTP*, *CAX2*, *AtMHX* [89-91] or the *AtNramp, AtPDR8*, and *AtATM3* genes of ABC transporters [98, 99]. For lead accumulation, the following transgenic plants were studied: tobacco plants expressing the calmodulin-binding protein gene of *Nicotiana tabacum* (*NtCBP4*) [100] and *Arabidopsis* plants expressing the *ZntA* [101], which codes for the zinc transporter in *E. coli*, and an enhanced accumulation of lead, as well as other heavy metals, was observed. The yeast *YCF1* gene codes for a transporter of vacuolar storage of Cd/Pb. *A. thaliana* expressing the *YCF1* gene showed a high resistance to Cd and Pb and accumulated those heavy metals [102]. Transgenic poplar trees expressing the *YCF1* gene also developed a high resistance to Cd and Pb [103]. Moreover, a study conducted by Mizuno et al. showed that transgenic *A. thaliana* had longer roots (2.5 times longer) and a higher (3–14 times higher) accumulation of lead when the *FeMRP3* gene of buckwheat was expressed in *A. thaliana*.

#### **3.6. Assessment of efficiency of phytoextraction**

The author assessed the efficiency of phytoextraction in contaminated soil by lead. The most advantageous point of phytoremediation is its profitability. By the author's rough estimate, the income generated by the phytoremediation process is approximately 340, 000 dollars/ha for cases where it is assumed that (1) pollution is present at 1 m in depth and 10 g/kg of lead is contained in the soil (density: 1.7), (2) 100 % of the lead is extracted from the soil, and (3) the price of lead is 2, 000 dollars/ton. However, the approximation of the necessary expenses is much higher according to some reports and are estimated to be as high as 300, 000–5, 000, 000 dollars/ha (lowest estimation: 2, 500–15, 000) [104]. The difference in the costs suggests that further efforts are necessary to decrease the expenses in order to improve the application of phytoextraction.

The high necessary expenses of phytoextraction are due to the low yield per treatment period and the time-consuming posttreatment heavy metal recycling from the biomass. Even in buckwheat, which is one of the best hyperaccumulators for lead, the amount of lead absorption is only 20 kg/year (dual cropping), when the yield and adsorption ability are assumed to be 1 t/ha and 10 g/kg. Moreover, the plant absorbing lead must be dried, burned, and extracted to recycle the lead. The cost for those operations accounts for half of the total cost. Consequently, a hyperaccumulator with a fast growth time and a fast absorption rate, as well as a high accumulation ability, is required to overcome the problem of high necessary expenses.

Furthermore, the effect on the environment should be considered. Indigenous species do not necessarily have a superior ability for phytoremediation, although the use of indigenous species is acceptable [105]. The planting of a nonnative hyperaccumulator often changes the natural flora or may destroy the indigenous species because hyperaccumulators have an increased ability to adapt to the environment. This is particularly true for transgenic plants. Therefore, special consideration for the environment and a general consensus in the society are necessary.

In conclusion, further efforts to decrease the necessary expenses must be undertaken for the widespread use of phytoextraction, although phytoextraction is a remarkable procedure for recycling lead in the soil. For example, some weeds are capable of easily and rapidly repro‐ ducing even when most of the shoots and leaves are removed. The advantages of using a weed for phytoextraction include the following: (1) lead can be continuously obtained from the leaves and shoots, (2) the growth and absorption can be completed in a short period of time, and (3) the posttreatment is inexpensive. Therefore, the author suggests that the ideal phy‐ toextraction process includes the use of such a weed.


**1. Introduction**

Corrosion can be defined as an attack on materials because of an interaction of materials with the surrounding environment. Based on this definition, all materials can corrode. But in practice, the term corrosion is mainly associated with the degradation of metals [1]. Metals are widely used materials due to having remarkable properties such as high electrical and thermal conductivity, ductility, malleability, and high strength. Apart from gold, platinum, and a few others, most metals are prone to corrosion. This problem can be more important when using metal alloys as the type, speed, and rate of corrosion are different for each element. In fact, more than one type of corrosion can occur in the corrosion of alloys. Corrosion is a common and costly phenomenon that should be prevented to avoid irreparable risks such as damage to structures and human life. There are several factors that influence the rate of corrosion including diffusion, temperature, conductivity, humidity, type of ions, pH value, and electrochemical potential [2]. The corrosion rate of metals can be controlled or reduced by taking various measurements. The most common methods include

cathodic protection, galvanizing, painting, and coatings. Coatings are probably the most convenient method to prevent the corrosion of metals due to the low cost, availability of raw materials, flexibility, and simplicity. There are many different types of industrial coatings, including organic (alkyd coatings, epoxy coating, polyurethane coatings, etc.) and inorganic coatings (ceramic coatings, metalized coating, etc.).

Despite having many advantages, coatings are subject to problems such as cracking and degradation. Therefore, they must be repaired or replaced. Being exposed to a corrosive environment for a long time leads to the weakening of the mechanical properties of the coating, and as a result, microcracks form and propagate. The failure of the coatings is inevitable and hence they must be repaired or replaced. In order to improve the properties of the coatings, several methods such as adding fillers in a polymer matrix have been proposed and implemented. Various fillers including zinc oxide, titanium dioxide, and silicon dioxide have been used and commercialized which enhance both mechanical properties and corrosion inhibition performance of coatings. During the past two decades, new-generation protective coatings, self-healing coatings, have been introduced and developed that can repair the damage caused by corrosive media and as a result, increase the coating lifetime. Self-healing coating has become a research hotspot in the coating field. Thus underlying their properties, mechanism, and synthesis procedures could be interesting. However, the development of these coatings is still in its early stages and it is very important to know their various aspects, including their properties, mechanism, performance, and application. This chapter provides basic information about metal corrosion and the development of methods to inhibit this phenomenon. In addition, different mechanisms of self-healing materials and published reports in this field are reviewed.


Paranasal Sinuses - Surgical Anatomy and Its Applications

*Edited by Balwant Singh Gendeh*

Published in London, United Kingdom

Paranasal Sinuses - Surgical Anatomy and Its Applications http://dx.doi.org/10.5772/intechopen.107675 Edited by Balwant Singh Gendeh

#### Contributors

Balwant Singh Gendeh, Daniel F. à Wengen, Dragan Krasic, Ferit Bayram, Gokhan Gocmen, Hardip Singh Gendeh, Karamveer Narang, Karan Jolly, Kharoubi Smail, MengDi Zhang, Milos Trajkovic, Natalya Serova, Nebojsa Stojanovic, Olga Pavlova, Ozan Ates, Sergey Ternovoy, SiRui Guo, Stasa Krasic, Ya Mo, YueJiao Yao

#### © The Editor(s) and the Author(s) 2024

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Recent Advances in Plant in vitro Culture

*Edited by Annarita Leva and Laura M. R. Rinaldi*

**RECENT ADVANCES IN**

Edited by **Annarita Leva**  and **Laura M. R. Rinaldi**

**PLANT** *IN VITRO* **CULTURE**


**4. Analysis of interviews**

In this section, the resilience of residents in Dutch neighborhoods is analized on the basis of ten interviews with key persons. In the appendix, a short description is given of the interviewees and their involvement into the subject. In the report, randomly assigned letters refer to the ten interviewees. The reporting is in the order of the elements of the conceptual model. However, we start in the center of the model with the descriptions of the concept of resilience, as given by the interviewees.

#### **4.1 In-practice definitions or resilience**

Most interviewees relate the term resilience to social progress. C gives a rich description: 'It is a wonderful word. It includes strength and optimism. It expresses dynamics. It dents in and out and brings you further. […] It helps to make connections. It is taking blowes as well'. According to A, resilience can be triggered by experiences of inequality. 'You have to rely on your inner anchor', says E. F adds to that: 'It has to be tensive. If you cannot lose, you cannot win.' However, some conditions have to be met in order to be resilient:. 'Have attention for the problems. […] One needs to have a safe base. One needs to be sheltered and to have a basic income', D states.

Remarkably some interviewees address individual differences in resiliency. Some people show no tendency to be resilient (A). 'They are probably not self-reliant, nor will they become so. And (yet) we pretend that it will happen. Everybody resilient in the neighborhoods, everybody happy', A relates. Used in this way, resilience has become an empty word, H states. Furthermore, F suggests to mobilize the silent force of modest people as well: 'They are not the people who are always omnipresent in the commissions and meetings in the neighborhood.' Resilience concerns the relationship between people and their environment: 'What you inflicts on the planet, you inflict do on yourself. If you are not be aware of that, it becomes a zero sum game.' It is a referral to spillover effects and lack of environmental responsibility.


*2.1. Materials*

All of the compounds chosen for this research were conducted without additional purification. Zinc acetate dihydrate (Zn(CH3COO)2·2H2O) (BHD, Poole, UK), silver nitrate AgNO3 (Sigma, Ronkonkoma, NY, USA), hexamethylenetetramine (C6H12N) (HMTA, Merck, Darmstadt, Germany). The ammonia (NH3) and ionized water were available in the laboratory of School of Physics Universiti Sains Malaysia.

#### *2.2. Preparation of Ag-Doped ZnO Thin Films and Measurements*

The simple hydrothermal method was employed to synthesize Ag-doped ZnO thin film growth on the glass. The solution was prepared by mixing 0.1 mol of Zinc acetate dihydrate and 0.1 mol of hexamethylenetetramine in 100 mL of ionized water. After that, the mixture was vigorously stirred for half hour. AgNO3 (0, 0.5, 1.0, 3.0, and 5.0 wt%) was introduced to the prepared solution and continuously stirred for 1 h to obtain a homogeneous solution. Then, NH3 was added dropwise into the solution until the transparent solution was acquired. The solution was then poured into 150 mL Teflon autoclave, with the immersion of the glass substrate (slab glass that deposited the thin films on it), before it was closed tightly and heated at 180 ◦C in the furnace for 12 h, after which it was cooled to ambient temperature. The thin film was rinsed several times using deionized water. Finally, the sample was annealed at 400 ◦C for 1 h in the furnace for impurity removal. This procedure was performed several times for different concentrations of Ag, as previously mentioned.

Meanwhile, the structure analysis of pure ZnO and Ag-doped ZnO thin films was measured by X-ray diffraction (XRD) (Malvern PANalytical, Malvern, UK) and equipped with a Cu-K emission wavelength at (0.154 nm), for the range of 2θ at 20◦ ≤ 2 θ ≤ 80◦. Besides that, the morphology of the thin films was studied by scanning electron microscope (SEM) (JSM-6460LV SEM JEOL Ltd, Tokyo, Japan). The nanocomposite of the thin films was depicted via energy-dispersive X-ray (EDX) (Tokyo, Japan) analysis. In addition, photoluminescence (PL) (Jobin Yvon HR 800 UV Jobin Yvon, Kyoto, Japan) was investigated using a laser with a power of 0.18 mW, and the excitation source's wavelength was 325 nm. Ultraviolet visible (UV–vis) spectrophotometry (Model Cary 5000 UV-VIS-NIR Agilent Technologies, Santa Clara, CA, USA) was applied to measure the transmittance.


**1. Introduction**

The consumption of fresh fruits and vegetables is essential for a healthy diet [1]. However, their production can be affected by microbial pathogens (mostly fungus) during the production chain [2]. In order to reduce the presence of pathogens, several post-harvest technologies have been applied [2]. One of them is the application of chemical fungicides; however, this practice is not accepted due to environmental and health issues [3]. Other alternatives are the use of eco-friendly substances such as generally recognized as safe (GRAS) compounds and emergent technologies like ultrasound and fogging. Currently, consumers demand fresh products free of chemical residues; therefore, it is necessary to develop technologies eco-friendly, effective to protect against pathogens infection, and that these technologies can maintain the fruit quality. Alternative systems such as edible coatings, essential oils, salts, natural compounds (plant extracts), among others to chemical use are suitable approaches for post-harvest disease management. These alternatives can be applied in combination with other control systems like emerging technologies (ultrasound) in order to improve their efficacy. The aim of this chapter is to make a compilation of several studies conducted on fruits for controlling important pathogens in several crops.