specifically , the main body of the trypsinizing zone in the invention is a cylinder , which is equivalent to or slightly larger than the seed reactor in volume . the ratio of height to diameter of the said cylinder is about 0 . 5 ˜ 1 . 5 . the said cylinder may be made of stainless steel or glass . the said cover is hermetically affixed to the top of the cylinder . the said cover may be made of stainless steel . in the center of the cover , there is a hole through which extends the pivot of the agitation device . along the peripheral part distal to the said center are distributed the said feed inlet ( s ) for introducing the culture from the previous seed bioreactor , and the said gas outlet ( s )/ inlet ( s ) for introducing the sterile gas to control the pressure and the atmosphere in the said cylinder . the exit of the gas pipe ( s ) in the cylinder must be above the liquid level therein . all the said inlets and outlets are hermetically connected to the said cover in a fluid interconnection . for this purpose , many means and methods are available and well - known in the art . in one embodiment of the invention , the seal between the said cylinder and the said cover is accomplished by placing an o - ring in the cover flange and secure the upper edge of the cylinder in the seal groove in the o - ring . surrounding the cylinder , there may be several fixing bolts vertically extending from the bottom to the cover symmetrically distributed in order to press the said cover , cylinder and bottom to form strict seals among each other . the agitating device of the invention may be , for example , anchor impeller agitator , arrow - shaped paddle , disk agitator , pitched turbine agitator and crew propeller agitator , which may be arranged in monolayer or multilayers . the diameter of the paddle of the agitator is about 30 ˜ 95 % of the inner diameter of the said cylinder . the lowest paddle is about 3 ˜ 50 millimeters vertically distant from the upper surface of the screen . the hermetic and rotatable attachment between the agitating device and the cover may be accomplished via , e . g ., mechanical pivot gland or magnetic transmission sealing techniques . the main body of the said separating zone is the said bottom that is hermetically connected to the said cylinder . the said bottom may be of any type commonly used in the bioreactors . also , it may be modified into a conical shape . the said bottom may be made of stainless steel . it is hermetically connected to the cylinder in usual ways . in one embodiment of the invention , the seal between the said cylinder and the said bottom is accomplished by placing an o - ring in the bottom and secure the lower edge of the cylinder in the seal groove in the o - ring . surrounding the cylinder , there may be several fixing bolts vertically extending from the bottom to the cover symmetrically distributed in order to press the said cover , cylinder and bottom to form strict seals among each other . the screen of the invention may be tightly affixed to the fixing ring by pressing , adhering or welding . then , the said fixing ring is placed in the bottom flange so that the screen and the flange of the bottom is in the same surface , see fig2 . the said screen may be selected from the commercially available types usually made of stainless steel or nylon . the mesh size of screen must be larger than the diameter of the cells and smaller than the diameter of the microcarriers , in order to retain the carriers with / without cells on the screen while permitting the detached cells to pass through . thereby , after the trypsinization and before the separation of the cells from the carriers , the trypsin solution can be completely removed , leaving the carriers with the attached cells retained in the trypsinizing zone , which advantageously prevents damaging the cells caused by the trypsin residue . moreover , during the said separation , the mesh size as said above permits the passage of the free cells through the screen into the bottom , but not the carriers . thereby , a single cell suspension is obtained in the bottom that are then discharged and transferred to the subsequent bioreactor . given the cell line and microcarrier , informations regarding the diameters of both the cells and the carriers are quite accessible to the skilled in the art , which makes the determination of the mesh size quite easy . in a preferred embodiment of the invention , the surface of the screen is siliconized in order to prevent the microcarriers from adhering to the screen to block the mesh and finally decrease the filtering efficiency . the siliconization may be carried out by using , for example , trimethyl chlore silane , dichlorodimethylsilane ( davis et al . ( ed . ), basic methods in molecular biology , prentice - hall international inc ( 1994 )) or hexamethyldisilane ( ezheng ( ed . ), tissue culture and molecular cytotechnology , beijing press , ( 1995 )). there are at least one inlet / outlet for the medium , at least one inlet for the wash solution / trypsin solution and at least one outlet for the wash solution / trypsin solution hermetically connected to the bottom in a fluid interconnection . the said inlet ( s )/ outlet ( s ) for the medium are used to introduce medium to make single cell suspension after trypsinization and , later , drain off the said suspension to be further transferred into the subsequent bioreactor for culture . the said inlet ( s ) for the wash solution / trypsin solution and outlet ( s ) for the wash solution / trypsin solution are controlled , as desired , by the valves in the connected pipelines . the said wash solution or the said trypsin solution is introduced through the reactor of the invention down to up , and drained off through the outlet on the bottom of the reactor after the treatment with either . in an embodiment of the invention , after the completion of the incubation in the previous seed bioreactor , the culture containing the seed cells attached to the microcarriers is introduced into the said trypsinizing zone of the said cell - detaching reactor through the feed inlet on the cover . sterile gas at appropriate pressure ( 0 . 01 ˜ 0 . 15 mpa constant pressure ) is introduced into the reactor through the gas inlet to raise the inner pressure of the reactor to dischage the supernatant through medium inlet / outlet at the bottom under pressure . alternatively , a pump , such as a peristaltic pump , may be used to drain off the said supernatant through the said medium inlet / outlet . additionally , other drainage methods well - known in the art can also be used alone or in combination . then , the wash solution is introduced into the cell - detaching reactor from the bottom through the said inlet ( s ) for wash solution / trypsin solution . after wash , the wash solution is discharged through the said outlet ( s ) for the wash solution / trypsin solution . then , trypsin solution is introduced into the cell - detaching reactor from the bottom through the said inlet ( s ) for wash solution / trypsin solution . during the trypsinization , agitator works at such a low speed that the trypsinization is carried out evenly throughout the said trypsinizing zone , while maintaining the cells attached to the microcarriers . after the trypsinization is completed , the trypsin solution is completely discharged through the outlet ( s ) for the wash solution / trypsin solution at the bottom . then , the medium is introduced into the cell - detaching reactor through medium inlet / outlet at the bottom , and the agitation is switched to a high speed to detach / separate the cells from the microcarriers . then , the resultant single cell suspension are discharged through the medium inlet / outlet at the bottom and , then , transferred into the subsequent bioreactor . the cell - detaching reactor of the invention can advantageously change the way of inoculation , significantly improve the culture efficiency and permit the scale - up of the anchorage - dependent cell culture . the cell - detaching reactor of the invention may be widely used in various applications including , for example , commercially culturing anchorage - dependent cells such as cho , bhk , vero cells , etc , to produce recombinant proteins , viral vaccines and recombinant virus for gene therapy . further scope of applicability of the present invention will become apparent from the detailed description given hereinafter . however , it should be understood that the detailed description and specific examples , while indicating preferred embodiments of the invention , are given by way of illustration only , since various changes and modifications within the spirit of the invention will become apparent to those skilled in the art from this detailed description . the present invention will become more fully understood from the detailed description given hereinbellow and the accompanying drawings which are given by way of illustrations only , and thus are not limitative of the present invention , wherein , [ 0036 ] fig2 shows the attachment and fixation of the screen in the cell - detaching reactor of the invention ; [ 0037 ] fig3 shows the flows of the materials in a typical operation of the cell - detaching reactor of the invention ; [ 0038 ] fig4 shows the growth profiles of vero cells inoculated form a 1 - liter seeds reactor using the cell - detaching reactor of the invention into a 5 - liter culture reactor . to culture the cho cells , the cell - detaching reactor of the invention is utilized to conduct the inoculation from a 1 - liter reactor to a 5 - liter reactor . the 1 - liter reactor has a work volume of about 0 . 7 liter and is used for microcarrier based culture . the 5 - liter reactor has a work volume of about 3 . 5 - liter and is a packed - bed based bioreactor . the structure of the cell - detaching reactor is shown in fig1 and the flow of the materials therein is shown in fig3 . the volume of the cell - detaching reactor is 3 . 5 liter . as shown in the fig1 - 2 , the cylinder 7 made of glass is 186 mm in height and 143 mm in diameter . the cover 8 is made of stainless steel . the agitator 5 is installed through the central hole ( not shown ) in the cover , and hermetically and rotatably affixed to the cover using the mechanical pivot gland . the o - ring ( not shown ) is fixed in cover 8 . four open holes for bolts 6 are distributed evenly along the periphery of the flange of the cover . as said above , the cover and the cylinder are hermetically connected by the flange , o - ring and fixing bolts 6 . the agitator 5 in this example is a monolayer of cambered stirring paddles , having a diameter of 95 % of that of the cylinder . the lower surface of the paddle is 50 millimeters distant from the upper surface of screen . the stirring paddle is affixed to the pivot of a driving motor by fixing screws ( not shown ). the bottom 4 is conical and made of stainless steel . the seal ring 13 is fixed in the seal ring cavity 13 in the bottom . four open holes for the bolts 6 are distributed evenly along the periphery of the flange 14 of the bottom . as said above , the bottom and the cylinder are hermetically connected by the flange , o - ring and fixing bolts 6 . the fixed ring 12 on which the screen is fixed is placed in the bottom . the screen 11 is a 200 mesh screen made of 316l stainless steel . it is known that the average diameter of cho cells is 15 μm and the microcarrier cytodex - 1 , 180 μm . thus , the mesh size of screen 11 is determined to be 60 μm . the screen is further siliconized with 2 % trimethylchlorosilane in chloroform . initially , phosphate buffer solution is introduced into the cell - detaching reactor . after autoclaved at 121 ° c . for 30 min , the cell - detaching reactor is connected , under sterile condition , to the 1l seed bioreactor via the feed inlet 10 on the cover and to the 5 - l culture bioreactor via the medium inlet / outlet 3 . when the cell density in the 1 - l seed bioreactor reaches 10 × 10 6 cells per milliliter , the culture is pressed into the trypsinizing region of the cell - detaching reactor through the feed inlet 10 by sterile gas . then , sterile gas at constant pressure of 0 . 1 mpa is introduced into the cell - detaching reactor through gas inlet / outlet 9 . thus , the supernatant of the culture is completely discharged through medium inlet / outlet 3 on the bottom under increased inner pressure . the microcarriers with attached cells are retained on the screen . wash solution preheated to 37 ° c . is introduced through inlet 1 for the wash solution / trypsin solution on the bottom . wash is conducted for about 1 min under agitation at 20 rpm . the inner pressure is increased again as said above to completely press out the wash solution through outlet 2 for the wash solution / trypsin solution . then , the trypsin solution preheated to 37 ° c . is introduced through inlet 1 for the wash solution / tyrosine solution on the bottom . trypsinization is conducted for about 6 min under agitation at 20 rpm . the inner pressure is increased again as said above to completely press out the trypsin solution through outlet 2 for the wash solution / trypsin solution . then , the culture medium preheated to 37 ° c . is introduced into the cell - detaching reactor through medium inlet / outlet 3 on the bottom , and agitated at 120 rpm for 6 minutes to detach the cells from the microcarriers . the inner pressure is increased again , as said above , to completely press the resultant single cell suspension out of the cell - detaching reactor through the medium inlet / outlet 3 . the said suspension is then transferred into the subsequent 5 - liter culture bioreactor at the seeding cell density of 2 × 10 5 cells / ml for further perfusion culture . after culturing for 11 days , the final cell density in the 5l packed - bed bioreactor is 1 . 2 × 10 7 cells / ml . to culture the vero cells , the cell - detaching reactor of the invention are utilized to conduct the inoculation from a 1 - liter reactor to a 5 - liter reactor . the 1 - liter reactor has a work volume of about 0 . 7 and the 5 - liter reactor , 3 . 5 - liter . both reactors are used for microcarrier based culture . the structure of the cell - detaching reactor is shown in fig1 and the flow of the materials therein is shown in fig3 . the volume of the cell - detaching reactor is 3 . 5 liter . as shown in fig1 - 2 , cylinder 7 made of glass is 186 mm in height and 143 mm in diameter . the cover 8 is made of stainless steel . the agitator 5 is installed through a central hole ( not shown ) in the cover , and hermetically and rotatablly affixed to the cover using the mechanical pivot gland . the o - ring ( not shown ) is fixed in the cover 8 . four open holes for the bolts 6 are distributed evenly along the periphery of the flange of the cover . as said above , the cover and the cylinder are hermetically connected by the flange , the o - ring and the fixing bolts 6 . the agitator 5 in this example is a monolayer of cambered stirring paddles , having a diameter of 30 % of that of the cylinder . the lower surface of the paddle is 3 millimeters distant from the upper surface of the screen . the stirring paddle is affixed to the pivot of a driving motor by fixing screws ( not shown ). the bottom 4 is conical and made of stainless steel . the seal ring 13 is fixed in the seal ring cavity 13 in the bottom . four open holes for the bolts 6 are distributed evenly along the periphery of the flange 14 of the bottom . as said above , the bottom and the cylinder are hermetically connected by the flange , o - ring and fixing bolts 6 . the fixed ring 12 on which the screen is fixed is placed in the bottom . the screen 11 is a 200 mesh screen made of 316l stainless steel . it is known that the average diameter of cho cells is 15 μm and the microcarrier cytodex - 1 , 180 μm . thus , the mesh size of the screen 11 is determined to be 60 μm . the screen is further siliconized with 2 % trimethylchlorosilane in chloroform . initially , phosphate buffer solution is introduced into the cell - detaching reactor . after autoclaved at 121 ° c . for 30 min , the cell - detaching reactor is connected , under sterile condition , to the 1 l seed bioreactor via the feed inlet 10 on the cover and to the 5 - l culture bioreactor via the medium inlet / outlet 3 . when the cell density in the 1 - l seed bioreactor reaches 1 . 3 × 10 6 cells per milliliter , the culture is pressed into the trypsinizing region of the cell - detaching reactor through the feed inlet 10 by sterile gas . then , sterile gas at constant pressure of 0 . 1 mpa is introduced into the cell - detaching reactor through gas inlet / outlet 9 . thus , the supernatant of the culture is completely discharged through medium inlet / outlet 3 on the bottom under the increased inner pressure . the microcarriers with attached cells are retained on the screen . wash solution preheated to 37 ° c . is introduced through the inlet 1 for the wash solution / trypsin solution on the bottom . wash is conducted for about 1 min under agitation at 20 rpm . the inner pressure is increased again as said above to completely press out the wash solution through the outlet 2 for the wash solution / trypsin solution . then , the trypsin solution preheated to 37 ° c . is introduced through the inlet 1 for the wash solution / tyrosine solution on the bottom . trypsinization is conducted for about 6 min under agitation at 20 rpm . the inner pressure is increased again as said above to completely press out the trypsin solution through the outlet 2 for the wash solution / trypsin solution . then , the culture medium preheated to 37 ° c . is introduced into the cell - detaching reactor through the medium inlet / outlet 3 on the bottom , and agitated at 120 rpm for 6 minutes to detach the cells from the microcarriers . inner pressure is increased again , as said above , to completely press out the resultant single cell suspension out of the cell - detaching reactor through the medium inlet / outlet 3 . the said suspension is then transferred into the subsequent 5 - liter culture bioreactor at the seeding cell density of 2 . 6 × 10 5 cells / ml for further perfusion culture . after culturing for 4 days , the final cell density in the sl bioreactor is 1 . 6 × 10 6 cells / ml . the growth profile of vero cells cultured in the 5 - liter reactor is shown in fig4 .