in order to achieve the advantageous results of the invention , it is crucial that the specific gravity be within a range which is effective to cause the beads to separate . if the specific gravity is too low , the beads will neither separate at the surface of the solution nor from the mold . if the specific gravity is too high , the beads will not form a layer separate from the mold or at the surface of the liquid . moreover , to the extent that the mixture of beads and mold float in the same layer , the layer will not separate at the surface of the liquid and the polymer beads cannot be recovered . suitable for use as nonionic adsorbents are porous fine particles having a large specific surface area and consisting of various synthetic resins , such as , polymers of one or more compounds selected from the group consisting of styrene , divinylbenzene , and acrylic esters . specific examples include adsorbents composed of styrene - divinylbenzene type synthetic resins , for example hp - 10 , hp - 20 , hp - 30 , hp - 40 , and hp - 50 , produced by mitsubishi kasei corporation ; amberlite xad - 2 and xad - 4 , produced by rohm and haas co . ; adsorbents composed of acrylic ester type resins , for example , amberlite xas - 7 , produced by rohm and haas co . ; and the like . particularly preferred among these nonionic adsorbents are those having a particle size of form about 50 to about 1 , 000 μm , a specific surface area of from about 50 to about 1 , 000 m 2 / g and a pore volume of from about 0 . 2 to about 1 . 5 ml / g . the specific gravity range which is effective to accomplish the desired result will vary depending on the particular nature of the broth , the mold and the beads . generally , we have found that a specific gravity range of from about 1 . 05 to about 1 . 20 is preferred . the specific gravity of the broth may be adjusted to the required value by the addition of an appropriate water soluble material , such as , an inorganic salt or an organic compound which is effective to change the specific gravity of the solution . typical of such salts and compounds are nacl , kcl , na 2 so 4 , mgso 4 , glycerol , glucose , sucrose , and combinations thereof . nacl is the most preferred material because it is the most economical . the absorbent polymer beads ( resin ) with the antibiotic adsorbed thereon can be recovered by physically separating the upper layer , e . g ., by filtration , decanting , and the like . the separated beads can then be washed with water , dried , and then subjected to an extraction step to extract the antibiotic . of course , any drying step would be carried out at a temperature which would not be adverse to either the beads or the antibiotic , e . g ., under 40 ° c . the raw antibiotics thus obtained can be subjected to conventional column - chromatographic purification directly , without recrystallization or reprecipitation . the extracted polymer beads can be re - used by removing the organic solvent , for example , by evaporation and then boiling with water . a sterile medium ( seed medium ) having the following composition was prepared in a 500 ml . flask , inoculated with streptomyces spectabilis atcc27465 , and incubated for 72 hours at 27 ° c . on a rotary shaker at 200 rpm . to produce a seed culture . ______________________________________seed medium : ______________________________________hydrolysed casein ( n - z - amine a ) 1 . 25 gglucose 0 . 63enzyme - decomposed extract 0 . 63of soybean ( soytone ) k . sub . 2 hpo . sub . 4 0 . 16kh . sub . 2 po . sub . 4 0 . 16distilled water 100 . 00______________________________________ a preproduction culture was prepared by inoculating a sterile medium ( preproduction medium ) having the following composition in a 500 ml . flask , with 2 ml of the foregoing seed culture and incubating for 48 hours at 27 ° c . on a rotary shaker at 200 rpm . ______________________________________preproduction medium : ______________________________________corn dextrin 2 . 0 gdefatted soybean meal 1 . 0 ( kay soy ) corn steep liquer 1 . 0beer yeast 0 . 25kcl 0 . 3caco . sub . 3 0 . 4distilled water 100 . 0______________________________________ a production medium having the following composition was inoculated with 5 ml of the thus obtained preproduction culture in a 500 ml flask and incubated for 6 days at 28 ° c . on a rotary shaker at 200 rpm . ______________________________________production medium : ______________________________________glucose 4 . 0 gsoybean meal 4 . 0beer yeast 0 . 25nacl 0 . 3caco . sub . 3 0 . 05mgso . sub . 4 0 . 25k . sub . 2 hpo . sub . 4 0 . 25diaion hp - 20 3 . 0 ( polystyrene beads - 50 % solid ) distilled water 100 . 0______________________________________ after 6 days , the mixture of hp - 20 ( resin ) and mold was removed from the broth by filtration . the mixture ( wet weight 10 g ) was then dispersed in a 20 % nacl solution ( specific gravity of 1 . 14 at 20 ° c . ), and left standing . the resin separated from the mold on the surface of the nacl solution and was recovered , leaving the mold at the bottom of the solution . after washing the resin with fresh water and drying it under a vacuum at 35 ° c ., it was extracted with 20 ml of ethyl acetate . 5 mg of crude streptovaricins containing 0 . 4 mg of streptovaricin c was obtained . the extracted resin could be reused as an adsorbent polymer after removing ethyl acetate under vacuum , and then boiling the resin in water . five nacl solutions having specific gravities of 1 . 04 , 1 . 07 , 1 . 15 , 1 . 20 , and 1 . 22 , were prepared and samples of the mixture of resin and mold obtained as in example 1 were dispersed within each of the solutions . clear separation was observed at specific gravities of 1 . 07 , 1 . 15 , and 1 . 20 , but not at 1 . 04 and 1 . 22 . 160 ml of the preproduction culture obtained from example 1 was inoculated in 3 liters of sterile medium having the following composition , which was prepared in a 5 liter jar fermenter . the medium was fermented for 9 days at 27 ° c ., 300 rpm and 1 v / v / m aeration . ______________________________________sterile medium : ______________________________________glucose 40 . 0 g / lsoybean meal 40 . 0beer yeast 2 . 5nacl 3 . 0caco . sub . 3 0 . 5mgso . sub . 4 2 . 5k . sub . 2 hpo . sub . 4 2 . 5monosodium fumarate 20 . 0defoamer ( km 75 ) 2 . 0diaion hp - 20 ( 50 % solid ) l00 . 0______________________________________ after fermentation , about 200 g of a wet mixture of resin and mold were obtained by filtration . the mixture was then dispersed in a 15 % kcl solution with a specific gravity of 1 . 10 at 20 ° c . and allowed to stand for 3 hours after which time the resin could be recovered from the surface of the solution . 0 . 5 g of crude streptovaricins , which included 150 mg of streptovaricin c , was obtained by extraction . the resin could be reused after evacuating the solvent and boiling with water . a fermentation was carried out as in example 3 . the contents of the jar fermenter were then transferred to a larger container and diluted to 10 liters . nacl was added to the container so that the specific gravity of the diluted broth was 1 . 14 . the solution was allowed to stand for 3 hours at which time the resin was recovered from the surface of the solution .