Abstract:
Improved screen filter modules, related compartmentalized filtration modules, and related filtration processes, suitable for filtering fluid to eliminate suspended particulate matter, such as living cells or microcarriers anchoring living cells, or to separate particulate matter based on size. The improvement is the presence of a barrier that channels redirected filtrate to the portion of the filter most susceptible to clogging by the particulate matter and induces flow patterns that act against clogging.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. provisional application 61/099,633 filed Sep. 24, 2008 and U.S. provisional application 61/099,813 filed Sep. 24, 2009. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to a device and methods for separating fluid from particulate matter such as living cells in suspension or attached to a solid matrix such as “microcarriers,” or nonliving particles suspended in the fluid. 
       BACKGROUND OF THE INVENTION 
       [0003]    Living cells suspended in fluid growth medium, for example in a bioreactor, have been used to generate pharmaceutically useful molecules. In many cases, the molecules produced by the cells are discharged into the growth medium; in other cases, the product is within the cells or may constitute the cells themselves; simultaneously, in search of increased productivity, the practice of cell culture has evolved. In one culture method, cells are grown in a continuous manner and to high concentrations by removing waste products from the culture and replacing with fresh media. In many cases, therefore, separation of cells from growth medium becomes an essential step in production of cell derived products. Separation of the molecules from the particulate cells in suspension or attached to microcarriers suspended in the growth medium can be achieved by a variety of methods. Not excluding other suspensions or solutions, the focus going forth will be on the use of anchorage dependent cells cultured on microcarriers. One separation method involves a “screen cage” with a mesh of pore size smaller than the microcarriers. The cage, in many cases, is placed in the culture vessel itself, and when appropriate, can be used to separate microcarriers from suspending medium, retaining the microcarriers within the vessel. The screen cage, while used in numerous processes, has a number of flaws, including that it is prone to clogging. Once clogged, it becomes useless and may result in premature termination of the production run at great cost and time loss. Furthermore, the volume of the internal screen cage reduces the capacity of the culture production vessel. 
         [0004]    Another method, somewhat like an external screen cage or using a chamber and a partitioning screen, has been used for separation of microcarriers from culture medium. It involves continuous pumping of culture suspension through the screen. The screen retains the microcarriers and the media flows through. This device results in concentration of microcarriers within the separation chamber; however, while effective for short separation steps, it may result in entrapment of the microcarriers within the screened chamber causing its eventual clogging. Another limitation of this method, inherently results from the concentration of microcarriers with attached cells within the chamber during the separation process, a process that can deprive the cells of essential nutrients and lead to cell damage. 
         [0005]    Another method for separating microcarriers from a culture medium involves a settling process, involving the of use of microcarriers, with attached cells, that together are heavier than the suspending medium. In a static culture, without agitation, the microcarriers, which are of specific gravity greater than the suspending medium, will settle to the bottom of the culture vessel, allowing removal of microcarrier-free medium from the top. While this method is reliable and commonly used, it is not preferred. The settling process is slow and time consuming, particularly at large scale, where settling distances are great. In addition, maintaining the cells in an unagitated environment can deprive the cells of oxygen and other nutrients. The current invention is designed to alleviate some of the limitations of other current systems. 
         [0006]    The prior art provides filters that allows the molecules, but not larger particulate matter or cells to pass through it. In order to maximize the production of the molecules, systems have been developed to replenish the medium removed from the suspended entities during the filtration step. This has been achieved in the prior art using alternating tangential flow systems (See U.S. Pat. No. 6,544,424). The system described in that patent, however, are not well adapted to disposability nor does it provide a mechanism for controlling the flow dynamics across the filter surface that may enhance the capacity and efficiency of the filter. The use of a device that can controls the flow dynamics or patterns across the filter membrane may be used to enhance the effectiveness of the filter. The term filter includes, but is not limited to, any of ultrafiltration filters microfiltration filters, macrofiltration filters as well as screens. The ability to control the flow dynamics across a screen filter facilitates its use, as exemplified, in production of vaccines, a multistep process; examples of the steps include an initial wash of microcarriers, meaning rapid removal suspending media through the screen filter and retaining the microcarriers and replenishing removed media with fresh media. Such step may be repeated more than once; another step, follows steam sterilization of the suspended microcarriers, which also requires a rapid media exchange step, removing sterilization media and replacement with fresh growth media, so that the subsequent inoculation with cells will result in rapid attachment and growth of the cells on the microcarriers; a further step may include removal of growth media from the culture, retaining microcarriers and attached cells, followed by addition of a second, production, media and simultaneously inoculation with a virus; following viral growth phase, the virus laden cells may result in cell lysis; in which case, the screen filter may be used to separate and harvest the virus, retaining the microcarriers and cell remnants in the culture vessel. Facilitation of such multistep process by an efficient separation device such as described by the invention can greatly enhance the viral production process and making the process more efficient, reliable and cost effective. it would be desirable to have a less expensive system, preferably one that could be considered disposable. A disposable system would not have to be washed or prepared for use, time consuming efforts that decrease system reliability and increase operating costs It would also be simpler to dispose of and replace a spent system by an unused filter module as needed. 
         [0007]    The present invention provides an enhanced screen filter module that can be used in a disposable manner if desired and an enhanced means for controlling the flow dynamics across a filter to enhance its filtration capacity and its usefulness in a greater range of applications. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    In its most general aspect, the invention is an improved screen filter module suitable for filtering fluid to separate suspended particulate matter, such as living cells or microcarriers anchoring living cells. The screen module is one adapted for use with an alternating pump that pulls the fluid through filter and then redirects a portion of the filtrate back through the filter. The module comprises a chamber within which, for example, particulate matter may be retained. The filter screen is part of the chamber wall. The improvement is the presence of a barrier that channels the redirected filtrate to the portion of the filter screen most susceptible to clogging by the particulate matter and generates flow dynamics within the filter chamber that inhibits clogging of the filter screen. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1   a  is a sectional view showing components and compartments of an assembled filtration module of the invention, also showing non-sectional views of portions of the assembly. The sectional view of the screen filter module within the compartmentalized filtration module is taken along the line  1 - 1  in  FIG. 2 . 
           [0010]      FIG. 1   b . Enlarged view of the indicated portion of  FIG. 1   a.    
           [0011]      FIG. 2  is a side view of a screen filter module of the invention, which module is shown in section as part of a. 
           [0012]      FIG. 3  is a sectional view of the screen filter module shown in  FIG. 2 , taken along the line  3 - 3  in  FIG. 2 . 
           [0013]      FIG. 4  is a side view of a screen filter module of the invention, which module employs a pleated screen filter. 
           [0014]      FIG. 5  is a top view of the module shown in  FIG. 4 . 
           [0015]      FIG. 6  is a 4× enlarged view of the indicated portion of  FIG. 7 . 
           [0016]      FIG. 7  is a sectional view of the screen filter module shown in  FIGS. 4 and 5 , the view taken along the line  7 - 7  in  FIG. 5 . 
           [0017]      FIG. 9  is a sectional view of the screen filter module shown in  FIG. 4 , taken along the line  9 - 9  in  FIG. 4 . 
           [0018]      FIG. 8  is a sectional view of the screen filter module shown in  FIG. 4 , taken along the line  8 - 8  in  FIG. 4 . 
           [0019]      FIG. 10  is a partial sectional view of a compartmentalized filtration module of the invention. 
           [0020]      FIGS. 11   a  and  11   b  are versions of  FIG. 10  in which arrows describe flow patterns if fluid is present in the compartmentalized filtration module.  FIGS. 11   a  and  11   b  show the flow patterns in opposite directions, depending on the force exerted by the alternating pump used in the compartmentalized filtration module. 
           [0021]      FIG. 11   c  is an enlarged view of the indicated portion of  FIG. 11   a.    
           [0022]      FIG. 11   d  is an enlarged view of the indicated portion of  FIG. 11   b.    
           [0023]      FIG. 12 . Isometric view of the screen filter module shown in  FIG. 10 . 
           [0024]      FIG. 13 . Sectional view of the screen filter module shown in  FIG. 12 . 
           [0025]      FIG. 14 . Sectional view of a compartmentalized filtration module of the invention, also showing a non-sectional views a portion of the module, the views being center isometric, the module an example of one where the flow barrier is internal to the retentate chamber. 
           [0026]      FIG. 15 . Sectional view of the compartmentalized filtration module of the invention shown in section in  FIG. 14  wherein the sectional view is along the line  15 - 15  in  FIG. 14 , but for the entire module, not just the portion of the module shown in cross section in  FIG. 14 . 
           [0027]      FIG. 16 . Variation of invention shown in  FIG. 10 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0028]    The invention has six general aspects: 
         [0029]    In a first aspect, the invention is a screen filter module enhanced with an external barrier, the module comprising: 
         [0030]    a) a retentate chamber, said chamber comprising a chamber wall and a chamber entrance, said chamber entrance permitting fluid containing suspended particulate matter (for example, fluid from a bioreactor) to enter or exit the chamber, and wherein the chamber wall comprises a filter screen, said screen comprising pores, such that said screen permits fluid and particles smaller than the pores but not suspended particulate matter larger than the pores to flow through it; 
         [0031]    b) a barrier, said barrier positioned exterior to the retentate chamber so as to redirect fluid moving through the filter screen area proximal to the chamber entrance so that the redirected fluid moves towards a filter screen area more distal to the chamber entrance; 
         [0032]    c) an exiting space between the filter screen and the barrier, said space for permitting fluid flow; 
         [0033]    d) an opening between the filter screen and the perimeter of the barrier, said opening providing a means for fluid to leave the exiting space and escape the module; and 
         [0034]    e) an upper adapter for attachment to the (preferably tubular) filter screen (preferably at the upper end of said screen when said screen with its main axis vertically disposed), said adapter also attached to a rigid portion of the screen filter module, so as to prevent collapse of the_filter screen. 
         [0035]    In the first aspect of the invention, it is optional and preferable that the filter screen module further comprise a base adapter for attaching the barrier to the retentate chamber and/or anchoring the filter screen when used in a compartmentalized filtration module. 
         [0036]    In a second aspect, the invention is a screen filter module enhanced with an internal barrier, the module comprising: 
         [0037]    a) a filtrate chamber, said chamber comprising a chamber wall and a chamber entrance, said chamber entrance permitting fluid to exit or enter the chamber, and wherein the chamber wall comprises a filter screen, said screen comprising pores, such that said screen permits fluid and particles smaller than the pores but not suspended particulate matter that is larger than the pores, to flow through it; 
         [0038]    b) a barrier, said barrier positioned inside the filtrate chamber so as to redirect filtrate chamber fluid moving towards a filter screen area distal to the filtrate chamber entrance so that the redirected fluid moves within the filtrate chamber towards a filter screen area more proximal to the filtrate chamber entrance and exits the filtrate chamber so as to flow into the retentate chamber; 
         [0039]    c) an opening in said barrier to allow limited fluid flow through the barrier; 
         [0040]    d) a bypass space between said barrier and the filtrate chamber wall, said space for permitting fluid entering the filtrate chamber through the filter screen to bypass the barrier and flow to the filtrate chamber exit; and 
         [0041]    e) a lower adapter attached to the filter screen. 
         [0042]    In the second aspect of the invention, it is optional and preferable that the filter screen module further comprise a base adapter for attaching the barrier to the filtrate chamber and/or anchoring the screen filter module when used in a compartmentalized filtration module. 
         [0043]    In a third aspect, the invention is a compartmentalized filtration module (also referred to herein simply as a “filtration module”) that contains a screen module enhanced with an external barrier such that the screen filter module comprises a retentate chamber, the filtration module comprising: 
         [0044]    a) a retentate chamber, said retentate chamber comprising a retentate chamber wall and a retentate chamber entrance, said entrance permitting fluid containing suspended particulate matter to enter and exit the chamber, said retentate chamber wall comprising a filter screen, said screen comprising pores, such that said that said screen permits fluid and particles smaller than said pores but not suspended particulate matter larger than the pores to flow through it; 
         [0045]    b) a filtrate chamber adjoining said retentate chamber, said filtrate chamber comprising a filtrate chamber wall and a filtrate chamber entrance, said filtrate chamber wall comprising the filter screen also comprised by the retentate chamber wall, said filtrate chamber entrance permitting fluid to enter or exit the filtrate chamber; 
         [0046]    c) an alternating pump connected to the filtrate chamber entrance, said pump for pumping fluid in alternating directions through the filtrate chamber entrance and thereby for pumping fluid in alternating directions through the filter screen; 
         [0047]    d) a barrier, said barrier positioned inside the filtrate chamber so as to redirect fluid moving through the filter screen area proximal to the retentate chamber entrance so that the redirected fluid moves towards a filter screen area more distal to the retentate chamber entrance; 
         [0048]    e) an exiting space between the filter screen and the barrier, said space for permitting fluid flow; 
         [0049]    f) an opening between the filter screen and the perimeter of the barrier, said opening providing a means for fluid to escape the exiting space and the retentate chamber; 
         [0050]    g) an upper adapter for attachment to the (preferably tubular) filter screen (preferably at the upper end of said screen when said screen with its main axis vertically disposed), said adapter also attached to a rigid portion of the screen filter module, so as to prevent collapse of the filter screen; and 
         [0051]    h) a harvest port for removing fluid from the filtrate chamber. 
         [0052]    In the third aspect of the invention, it is optional and preferable that the filter screen module further comprise a base adapter for attaching the barrier and/or anchoring the filter screen module in the compartmentalized filtration module. 
         [0053]    In a fourth aspect, the invention is a compartmentalized filtration module that contains a screen filter module enhanced with an internal barrier such that the screen filter module functions as the filtrate chamber, the filtration module comprising: 
         [0054]    a) a retentate chamber, said retentate chamber comprising a retentate chamber wall and a retentate chamber entrance, said entrance permitting fluid containing suspended particulate matter to enter and exit the chamber, said retentate chamber wall comprising a filter screen, said screen comprising pores such that said screen permits fluid and particles smaller than said pores but not suspended particulate matter larger than said pores to flow through it; 
         [0055]    b) a filtrate chamber adjoining said retentate chamber, said filtrate chamber comprising a filtrate chamber wall and a filtrate chamber entrance, said filtrate chamber wall comprising the filter screen also comprised by the retentate chamber wall, said filtrate chamber entrance permitting fluid to enter or exit the filtrate chamber; 
         [0056]    c) an alternating pump connected to the filtrate chamber entrance, said pump for pumping fluid in alternating directions through the filtrate chamber entrance and thereby for pumping fluid in alternating directions through the filter screen; 
         [0057]    d) a barrier, said barrier positioned inside the filtrate chamber for redirecting fluid moving towards a filter screen area distal to the filtrate chamber entrance so that said redirected fluid moves through the filter screen area more proximal to the filtrate chamber entrance; 
         [0058]    e) a bypass space between said barrier and the filtrate chamber wall, said space for permitting fluid entering the filtrate chamber through the filter screen to bypass the barrier and flow to the filtrate chamber entrance; 
         [0059]    f) an opening in said barrier to allow limited fluid flow through the barrier; 
         [0060]    g) a lower adapter for attachment to the filter screen, said adapter also attached to a rigid portion of the filtration module, so as to prevent movement of the filter screen; and 
         [0061]    h) a harvest port connected to said alternating pump, said port for removing fluid pumped from the filtrate chamber. 
         [0062]    In the fourth aspect of the invention, it is optional and preferable that the compartmentalized filtration module further comprise a base adapter for attaching the barrier to the filtrate chamber and/or anchoring the screen filter module in the compartmentalized filtration module. 
         [0063]    In a fifth aspect, the invention is a process for removing particulate matter from a fluid in which it is suspended, the process being an example of one that utilizes the screen filter module enhanced with an external barrier, the process comprising the steps of: 
         [0064]    a) feeding a suspension into a retentate chamber via an entrance in that chamber, said entrance being the retentate chamber entrance, said suspension comprising the particulate matter suspended in the fluid, said retentate chamber connected to a filtrate chamber via a shared filter screen in their respective walls, said filter screen comprising pores of a size that allow the fluid and particles smaller than the screen pores but not the suspended particulate matter that are larger than the screen pores to pass through, said filtrate chamber comprising an entrance connected to an alternating pump; 
         [0065]    b) directing the suspension at the filter screen so that fluid but not said suspended particulate matter passes through the filter screen, said directing achieved by the action of the alternating pump; 
         [0066]    c) collecting, in the filtrate chamber, the fluid that passed through the screen filter, said collected fluid being the filtrate fluid; 
         [0067]    d) removing a portion of the filtrate fluid from the filtrate chamber, thereby leaving unremoved filtrate fluid in the filtrate chamber; 
         [0068]    e) directing the unremoved filtrate fluid back at the screen filter, such filter screen directing achieved by the alternating pump exerting a force on said unremoved filtrate fluid, such that a barrier redirects filtrate fluid moving towards a filter screen area proximal to the retentate chamber entrance so that the redirected fluid moves towards a screen filter area more distal to the retentate chamber entrance; and 
         [0069]    f) repeating steps (a) through (e). 
         [0070]    In a sixth aspect, the invention is a process for removing particulate matter from a fluid in which it is suspended, the process being an example of one that utilizes the screen filter module enhanced with an internal barrier, the process comprising the steps of: 
         [0071]    a) feeding a suspension into a retentate chamber via an entrance in that chamber, said entrance being the retentate chamber entrance, said suspension comprising the particulate matter suspended in the fluid, said retentate chamber connected to a filtrate chamber via a shared filter screen in their respective walls, said filter screen comprising pores, said pores of a size that allow the fluid and particles smaller than the pores but not the suspended particulate matter that are larger than the screen pores to pass through, said filtrate chamber comprising an entrance connected to an alternating pump; 
         [0072]    b) directing the suspension at the screen so that fluid but not said suspended particulate matter passes through the filter screen, said directing achieved by the action of the alternating pump; 
         [0073]    c) collecting, in the filtrate chamber, the fluid that passed through the filter screen, said collected fluid being the filtrate fluid; 
         [0074]    d) removing a portion of the filtrate fluid from the filtrate chamber, thereby leaving unremoved filtrate fluid in the filtrate chamber; 
         [0075]    e) directing the unremoved filtrate fluid back at the screen filter, such directing achieved by the alternating pump exerting a force on said unremoved filtrate fluid, such that a barrier redirects fluid moving towards a screen filter area distal to the filtrate chamber entrance so that the redirected fluid moves towards a screen filter area more proximal to the filtrate chamber exit; and 
         [0076]    f) Repeating steps (a) through (e). 
         [0077]    In the sixth aspect of the invention, a portion of the fluid (preferably less than 50 percent, more preferably less than a third) is permitted to flow through the barrier which may have small openings. 
         [0078]    As can be seen from the modules exemplified in the drawings, it is preferable that the filter screen be elongated in the direction of its main axis and be symmetrical as possible around that axis. 
         [0079]    The materials used to make the filter screen module and the compartmentalized two-chamber module are preferably synthetic polymers or plastics so as to reduce material and production cost relative to a metal construction and make it more economical to treat it as a disposable module. Preferred plastic for the filter module body are polysulfone, polycarbonate, kynar and others, and for the base adapter, barrier, and upper adapter they are: polysulfone, polycarbonate, kynar and others, and the screen material they are: polyester, PVDF, Kevlar and others; preferably such plastics are high performance capable of withstanding steam sterilization or sterilization by other means. 
         [0080]    The filter screen is preferably made of pores separated by the minimal amount of plastic required for structural integrity and stability. The filter screen will most likely correspond to a foldable, collapsible mesh whose collapse is prevented in the module because of the rigid support provided by other portions of the module to which the mesh is adhered to. 
         [0081]    Pore sizes capable of preventing passage of living animal cells or microcarriers generally range, respectively, from 0.1 micron to 80 microns. Spherical microcarriers typically have a diameter in the range 100 to 500 microns, so the pore size will have to be less than the microcarrier diameter used. The pores normally required in such case is about 75 micron in order to allow desired molecules, present in the fluid, to pass through the filter but not the larger microcarriers. Examples of desired molecules are antibodies, viruses, and other pharmaceutically active molecules. The minimum size will depend on that needed to allow the molecules to pass through the filters. The molecules will be those that were produced by the living cells, and therefore normally be smaller than the cells or microcarriers. 
         [0082]    The pore size can also be chosen to allow particles of a larger size to be separated from particles of a smaller size. 
         [0083]    The screen filter module is preferably used with aqueous fluids, usually enhanced with regard to pH, salts and nutrients as needed for living cells. 
         [0084]    Sterilization of the screen filter module prior to use can be achieved by autoclaving or other forms of steam sterilization or sterilization by radiation or by chemical means. Sterilization of the compartmentalized filter module can be achieved by similar means. When using plastic materials, the components can, where necessary, be caused to adhere to each other using adhesives such as high temperature epoxies, cyanoacrylates, heat, mechanical coupling, ultrasonic welding, or solvents. The surface area of the filter screen is based on application and volume of culture to be processes, and is preferably in the range between 10 and 10,000 cm 2 . The length, diameter and configuration of the screen are not limited but may vary considerably based on application. 
         [0085]    The filter screen may be tapered, so that, in the first aspect of the invention, for example, its attachment diameter at the point it meets the module&#39;s upper adapter is smaller than the attachment diameter where it meets to the lower scaffold perimeter. 
         [0086]    When the module is part of a compartmentalized filter module of this invention, the entrances of the two chambers and the alternating pump are preferably aligned along the main axis of symmetry of the screen filter module. 
         [0087]    When the barrier is external to the filter screen, it preferably redirects fluid away from portion of the filter that extends from the filter entrance almost the entire length of the filter (preferably at least 50 percent (more preferably at least 70 percent) of the entire length, preferably not more than 99 percent of the entire length) towards where it meets the upper adapter. 
         [0088]    The scaffold element is a structural component that is added to prevent collapse of the filter screen and/or its movement when subjected to fluid moving under pressure. For screen filter modules which are intended to be used while vertically disposed with the retentate chamber entrance at the lower end, the upper end of the filter screen (along with the attached upper adapter) would collapse under the force of gravity or stress created by the alternating flow, absent a scaffold element. The scaffold element in that case is preferably linked to the portion of the filter screen most distal to the chamber entrance (i.e., the higher end of the filter screen) to the surrounding barrier. The scaffold element may be attached directly to the filter screen or, preferably, indirectly by virtue of being attached to the upper adapter which in turn is attached to the filter screen. The scaffold element may be an extension of the barrier, and to some extent will therefore affect fluid flow but that is not its primary function. 
         [0089]    When the barrier is internal to the screen filter as in the second, fourth and sixth aspects of the invention, the screen filter module may be attached at its entrance end to the outer perimeter of the pump fluid chamber outlet. The other end of the module may be attached to a lower adapter. The lower adapter in turn is fixed within the filtration module by its attachment to the filtration module wall with a high strength bridge or link, preferably wire or thread that will not interfere with movement of retentate within the filtration module chamber. 
         [0090]    In addition to the advantages described above for the current invention, the invention is designed to allow or perform rapid separation steps of microcarriers or other particles from their suspending medium, as required in some production processes. It is also designed to allow rapid and continuous reversible flow of cells growing attached to the microcarriers between the culture vessel and filtration modules resulting in removal of cells from the culture vessel for only a short time, followed by the rapid return of the cells to the culture vessel where the cells are nourished. The reversible flow allows rapid equilibration of the content in the culture vessel with the culture in the filtration module, keeping the cells nourished and in good condition during the filtration process. As there may be several filtration steps during a production process, which may include several manipulations of the cultured cells, it is essential that the cells be maintained in optimally viable conditions during the filtration steps. Damaging the culture during any of the steps may be detrimental to the remainder of the production process. 
         [0091]    The inventions may be further understood by reference to the attached Figures. 
         [0092]      FIG. 10  illustrates a compartmentalized filtration module  401  that comprises a screen filter module  405 . The compartmentalized filtration module  401  is an example of the third aspect of the invention and the screen filter module  405  is an example of the first aspect of the invention. 
         [0093]      FIG. 12  shows a center isometric view of the screen module  405  of  FIG. 10 .  FIG. 13  shows a fully cross-sectional view of the screen module  405 .  FIG. 12  and  FIG. 13  together show that the screen filter module  405  is an example of the first aspect of the invention. The module comprises a retentate chamber  445 , a chamber wall  460 , a chamber entrance  443 , and a filter screen  417  that is part of the chamber wall. The chamber wall  460  comprises the screen filter  417  and a surface  534  of the upper adapter  441 . The module also comprises a barrier  419  exterior to the chamber  445  and further comprises an exiting space  464  between the screen filter  417  and the barrier  419 . The screen filter  417  adheres to upper adapter  441  by mechanical means ( FIG. 10 ) via an adhesive layer  526  ( FIG. 12 ; see also  FIGS. 4 ,  6 ,  7  and  13 ) or by other means. The upper adapter  441  is attached to the barrier  419  be means of fasteners, other mechanical means, heat, ultrasonic welding or adhesives; shown is attachment with a glue layer  527  and barrier adapter posts  449  that are part of the barrier  419  and that fit into the scaffold post receptacles (as shown for receptacles  300  in  FIG. 6 ) that are part of the upper adapter  441 . At the other end of the module, the screen and barrier are attached to the screen filter module base adapter  440 , (“also referred to as the “lower screen adapter”) the screen  417  by adhesive layer  448 , although other means of attachment are possible. Together, the upper adapter  441 , the base adapter  440 , the barrier  419 , and barrier adapter posts  449  provide support for the screen filter  417 , allowing it to be firmly stretched between the adapters  440  and  441 . The screen thus fixed at both ends to respective adapters  440  and  441  is firmly positioned, preventing its collapse during the stresses of the filtration process. The width of posts  449  is selected to optimize flow between retentate and filtrate chambers. Also considered in selecting the width of the posts is their indicated use as means of attaching adapter  441  with the attached screen  417  to the barrier body, where the width affects the flexibility of the post. Attachment of the post  449  to upper adapter  441  with a slight inward, (towards the center axis of the module), bend or tension so as to force the attached adapter  441  upward; thereby puling the attached screen  417  upward, maintaining it taught. The overcut  222  (lower portion of post  249 ), shown in  FIG. 4 , is designed to add flexibility to the post and to increase the range of bending. 
         [0094]    In  FIG. 13 , the majority of the fluid directed at the area  522  of the screen proximal to the retentate chamber entrance  443  will be redirected to the area  520  of the filter screen that is more distal to the retentate chamber entrance  443 . 
         [0095]    In  FIGS. 12 and 13 , it can further be seen that, between the filter screen  417  and the inner perimeter the restrictive platform  420 , (and therefore effectively between the filter screen  417  and the barrier  419 ) there is an opening  540 . The presence of the restrictive platform  420 , which is part of the barrier  419 , directs fluid, flowing from the pump exit end  478  (See  FIG. 10 ) into the filtrate compartment  410  (“compartment” and “chamber” are used interchangeably herein), into the retentate compartment  445 , through the upper area  418  of the screen  417  and restricts the fluid flow that otherwise would go into exiting space  464  between the screen  417  and the barrier  419 , areas of the screen that are more proximal to the retentate entrance opening  443 . 
         [0096]    The filter screen  417  will be porous, so as to allow fluid and particles smaller than the screen pores to pass through it. However, pores of the filter will be sufficiently small to retain and prevent suspended particulate matter larger than the screen pores to leave the chamber  445 . 
         [0097]      FIG. 10  shows a view of the compartmentalized filtration module  401  that comprises a screen filter module  405 .  FIG. 10  is a center isometric sectional view except for part of the screen filter module  405 . The screen filter module  405  is shown in a partially sectional isometric view that can be further understood from  FIGS. 11   a ,  11   b ,  12  and  13 . The compartmentalized filtration module  401  is essentially symmetrical around its longitudinal axis. (The harvest port  412  is, however, shown while only at one position is not limited to its length or configuration, nor are the numbers and positions of the post limited; preferably, harvest port opening  424  is positioned above the screen, such that when harvesting from the harvest port, removing air from the system and displacing it with liquid from the culture vessel flowing into the filtration module through the screen, thus immersing the screen in liquid and assuring full flow across the exit end  442  and upper screen area  418 , between retentate and filtrate compartments,  445  and  410 , respectively). 
         [0098]    In  FIG. 10 , the compartmentalized filtration module  401  comprises not only the screen filter module  405 , but also a filtrate chamber  410 . The filtrate chamber is enclosed by a filtrate chamber wall  504  that comprises the outer filtrate chamber wall  415  the base adapter plate  416  the filter screen  417  and an upper wall formed by the pump housing  404 , and specifically its external wall  433 . Accordingly, the filter screen  417  is part of both the filtrate chamber wall  504  and the retentate chamber wall  460  (See  FIG. 13 ). 
         [0099]      FIG. 10  also shows the alternating pump  404  which is connected to the filtrate chamber entrance  478  which, depending on the direction of fluid flow, can also function as the filtrate chamber exit. Here chamber entrance/exit  478  is also the pump opening through which fluid is exchanged between the pump and the filtrate chamber. The pump  404  comprises a fluid pump chamber  407 , an air pump chamber  408 , and a diaphragm  406  separating the fluid pump chamber  407  and the air pump chamber  408 . An air inlet assembly  421  that alternately directs compressed air into chamber  408  or exhausts that chamber is also shown connected to the pump  404 . 
         [0100]    Further evident in  FIG. 10  is a base adapter  510  which comprises an adapter plate  416  and a conical adapter  462 . The conical nature of the adapter inhibits settling of microcarriers on the adapter surface and facilitates their flow towards the fluid connector  403  through which fluid can flow from the retentate chamber entrance  443  to the culture vessel followed by flow from the culture vessel in the reverse direction. 
         [0101]    In  FIG. 10  the alternating pump  404  is connected directly to the filtrate chamber  410 . In a variation of the aspect of the invention illustrated in  FIG. 10 , the alternating pump is connected to the filtrate chamber by an intervening conduit  499  as shown in  FIG. 16 . 
         [0102]    Fluid flow across the filter screen  417  can be initially primed by activation of harvest pump  414  and removing air, through lines  412  and  413 , from the filtration module  401 , replacing air with liquid, flowing into the filtration module  401  through fluid connector  403 , which is connected at its other end to the culture container (not shown). Filling retentate chamber  445  with unfiltered retentate fluid, followed by flow into the filtrate chamber  410  into across screen  417 , filling both chambers and immersing barrier and screen in fluid so there is fluid contact between the chambers. Pressure on either the fluid within the chamber  445  or the fluid exterior to the chamber can be exerted by an alternating pump to move fluid through the filter screen. But the pores of the filter will be sufficiently small to prevent the suspended particulate matter larger than the screen pores to leave the chamber  445 , these capabilities in combination with harvesting liquid and particles smaller than the screen pores can be used to isolate small molecules that pass through the filter with the fluid or alternatively, by elimination of fluid from the chamber  445 , to isolate the particulate matter in more concentrated form. 
         [0103]    The restrictive platform  420 , the screen exit end  442 , and the barrier adapter posts  449 , can be understood by reference to  FIGS. 12 and 13  and the related descriptions. 
         [0104]      FIGS. 11   a  and  11   b  show the same compartmentalized filtration module  401  as is shown in  FIG. 10 , but shows how the direction of fluid flow is changed by the action of the pump  404 . 
         [0105]    In  FIG. 11   a , flow line arrows  470  shows air flow direction into the pump chamber  408 , pressurizing that chamber and forcing diaphragm  406  to expand into chamber  407 , forcing fluid from that chamber. Flow lines,  471 ,  473  and  474  illustrate one flow pattern for fluid directed by the pump  404  from the filtrate chamber  410  at the filter screen  417  is forced to flow to a filter screen exit end  442  (corresponding also to upper screen area  418 ), which exit end is distal to the retentate chamber entrance  443 . Flow thus generated will dislodge microcarriers or particulates attached to the corresponding, retentate chamber wall or inner screen wall  417 . The microcarriers thus dislodges will be diluted by the inflow of filtrate and forced to flow from the exit end  442  towards the entrance end  443  and back to the main culture via the fluid connector  403 . Absent the barrier  419 , the fluid emerging from pump  404  will flow from the filtrate side into the retentate side across the screen uncontrolled or directed. The flow across the screen may occur anywhere along the screen including predominantly at its base adjacent to the entrance  443 , which may in fact be the path of least resistance. Such flow would result in retaining microcarriers at increased concentration towards the distal end of the filter. Subsequent cycles of the pump and continued return of filtrate at the proximal end of the filter, at the entrance  443  side will further accumulate microcarriers at the distal end, which may eventually clog the screen. Continued removal of filtrate from the filtrate chamber  410  will add to the above indicated concentrating effect on the microcarriers. 
         [0106]    In  FIG. 11   b , flow line arrows  480  shows the exhaust of pump chamber  408  forcing diaphragm to move into the exhausted space of that chamber and inversely causing pump chamber  407  to expand and fill with the filtrate fluid. Arrows  481 ,  484 ,  485 , and  487  illustrate a second flow pattern for fluid directed by the pump  404  in a direction from the retentate chamber entrance  443 , into the retentate chamber  445 , through the filter screen  417  through filter exit end  442  and upper screen area  418 , into filtrate chamber  410 . The flow is completed by pump  404  return of the filtrate into pump chamber  407 . Noting the flow in this direction, towards the pump, it is preferable to have the flux of fluid flow from the retentate chamber to the filtrate chamber more uniformly distributed across the entire surface of the screen so as to minimize localized concentration of microcarriers within the filter module. More preferable, is that any concentration of microcarriers occur proximal to the entrance end  443  of the filter, to facilitate the return of microcarriers to the main culture vessel through fluid connector  403 . 
         [0107]    To facilitate objectives described in the above paragraph, secondary barrier openings  476  and a one directional check valves  477  are used. In the flow shown in FIG.  11   b , check valve  477  permit a fraction of the total fluid flow across screen  417  (see enlarged view  FIG. 11   d ) through barrier opening  476  from the proximal region to the entrance end  443  of the filter into filtrate compartment  410 ; thereby, reducing the concentrating microcarriers at filter distal end. Flow across the screen into exiting_space  464  facilitates this process. (This is further emphasized in  FIG. 1   a , by use of a constrictive “O” ring  30  around the screen  17  to permit greater unrestricted flow from the proximal end (proximal to entrance  43 ) of the retenate compartment to the filtrate compartment and through space  64 .) On the reverse flow shown in  FIG. 11   a , check valve  477  blocks flow through openings  476 , forcing the flow from the filtrate compartment to the retentate compartment through upper screen area  418  and adjacent screen region. These secondary barrier openings are optional and the degree of flow they allow when present does not change the fact that in  FIG. 11 , the majority of the fluid directed at the area  522  of the filter screen proximal to the retentate chamber entrance  443  will be redirected to an area  520  of the filter screen that is more distal to the retentate chamber entrance  443 . 
         [0108]    Also evident in  FIGS. 11   a  and  11   b  are the filtrate chamber  410 , and the retentate chamber  445 . Fluid flows from the retentate chamber into the filtrate chamber and then via the harvest port  412 , harvest pump  414 , and harvest line  413  for collection and/or further processing. 
         [0109]      FIGS. 4 through 9  together show a pleated version of a screen filter module  205  that is an example of the first aspect of the invention.  FIG. 4  is a side view except that part of that view, at the lower left, shows a side view with a portion of the barrier  219  absent. Without the barrier, the filter screen  217 , the adhesive layer  248 , and lower screen adapter (also a base adapter)  240  are visible. 
         [0110]      FIG. 4  shows a view of a version of the screen filter module  205  that contains a step  252  that is part of the lower screen adapter  240 . A similar step  52  that is part of the lower screen adapter  40  is shown in  FIGS. 1 and 2 ; its insertion into a counterpart receptacle  57  facilitates positioning and securing the screen filter module in a compartmentalized filter module (such as in  FIG. 1  where the step  52  facilitates insertion into a receptacle (socket) defined by the outer filtrate chamber wall  15  and the base adapter  110 .) An O-ring  251  ( 51  in  FIGS. 1 and 2 ) that encircles the lower screen adapter  240  ( 40  in  FIGS. 1 and 2 ) seals the lower screen adapter against the filter housing thus effectively preventing leakage of retentate into the filtrate compartment. 
         [0111]    The pleated version of the screen filter module  205  shown in  FIGS. 4 through 9  can be used the same as the screen filter modules shown in  FIGS. 1   a ,  1   b , and  10  through  13  and used in the compartmentalized filtration module  401  in a manner shown in  FIGS. 1 ,  10  and  11 . The lower screen adapter  240  and the O-ring  251 , shown in  FIGS. 4 and 7 , can be fitted into a housing similar to  415  in  FIG. 10  to form a fluid tight seal. The actual screen module shown in  FIG. 10  is, however, secured to base  510 . Cross-sectional views  FIGS. 8 and 9  show where the filter screen  217  has been gathered to form four pleats  246 . How the pleats  246  increase in size as one proceeds from the base to the top of the filter screen module is show not only by comparing  FIG. 8  to  FIG. 9 , but by viewing  FIG. 7 . While four pleats are shown, it is obvious that more or less pleats can be used, the depth of the pleats varies as well as their configuration. 
         [0112]    Evident in the module illustrated in  FIGS. 4 through 9  are the barrier adapter post  249  (also referred to as a scaffold element), the upper adapter  241  (also referred to as the scaffold adapter), the pleats  246 , the barrier  219  and the perimeter  227  of the barrier  219 . The scaffold adapter  241  is attached to the barrier  219  by means of barrier adapter posts  249  that are part of the barrier itself, where the posts fit into and are pinned or glued  327  to the scaffold post receptacles  300  that are part of the scaffold adapter  241 . Together, the upper adapter  241  and the barrier  219  provide support for the filter screen  217 , preventing its collapse during the filtration process. 
         [0113]    Also evident in the module illustrated in  FIGS. 4 through 9  are the retentate chamber  245 , upper screen area  218 , exiting space  264 , retentate chamber entrance  243 , and retentate chamber wall  260 . The chamber wall  260  comprises the filter screen  217  and a lower surface  334  of the upper adapter  241  and inner surface of lower screen adapter  240 . In  FIG. 4  adhesion layer  326 , attaching the screen to the upper adapter  241 , and adhesion layer  248 , attaching screen  217  to lower screen adapter  240 , are shown. 
         [0114]      FIGS. 1   a ,  1   b ,  2  and  3  together show another example of a reusable screen filter module  5  that is a first aspect of the invention as well as a compartmentalized filtration module  1  that utilizes filter module  5 .  FIG. 1   a  shows a filtration module that can be assembled or disassembled, noting the reversible “S” line sanitary connections, as common in the industry. Also shown are: fluid connector  3 , alternating pump  4 ,  6 , fluid chamber  7 , air pump chamber  8 , harvest line  13 , and sanitary connections and clamp  39  between parts; noting further, the sanitary gasket  25  used in such connections, including two adjacent flanges  37  and  38  and a clamp  39  to seal the flanges against the gasket to secure the seal.  FIG. 1   a  also shows filtrate chamber  10 , an, outer filtrate chamber wall  15 , barrier  19 , perimeter  27  of the barrier  19 , filter screen  17 , upper area  18  of the screen, air inlet adapter  21 , exit end  42 , retentate chamber entrance  43 , retentate chamber  45 , O-ring  51 , step  52 , surface  34  of the upper adapter  41 , the retentate chamber wall  60 , exiting space  64 , filtrate chamber entrance  78  (which overlaps with fluid chamber  7  and is not limited to the size shown) and the base adapter  110 , area  120  of the filter screen that is more distal to the retentate chamber entrance  43 , and area  122  of the screen proximal to the retentate chamber entrance  43 , opening  140  between the barrier perimeter  27  and the screen  17 , filtrate chamber wall  104  and the harvest port  12 . 
         [0115]    Also shown in  FIGS. 1   a ,  1   b ,  2  and/or  3  are a center post  128  that is connected to and supports the upper and lower screen adapters,  41  and  40 , respectively, where ledge  58  in post  128  upholds adapter  41  from sliding down and a pin or set screw  53  secures post  128  to the lower screen adapter  40 . Opening  54  in adapter wall  40  provides access to the set screw with a wrench or a tool for maneuvering the screw or pin  53  into opening  55  and forcing the screw against post  128  to secure its position against the lower adapter  40 . Noting “O” ring  26 , to which one end of the screen is mechanically attached, by sewing or other means, The “O” ring, in turn is mechanically secured against the base adapter  40 , also by common means; similar attachment of an “O” ring to the second end of the screen and their attachment to the upper adapter  41  is achieved; thereby, having the ability to slide adapter  40  against post  128  and securing the two adapters with screw  53  allows extension of the screen  17  between the two adapters and keeping it taught. Also shown is a pressure meter  130  to monitor pressure changed within the filtration module. Other instruments may be added by those skilled in the art to monitor various parameters within the filtration module; an air inlet assembly  32  containing a sterilizing air filter and the means for attaching to air inlet port  21 . The double arrow  23  illustrates the two directions for air flow to and from pump chamber  8 , resulting in pump action. 
         [0116]      FIGS. 14 and 15  together demonstrate another variation of the screen filter module  605  and the compartmentalized filtration module  601 . The variations are the second and fourth aspects of the invention (used for the sixth aspect), respectively. While variation in  FIG. 14  shows a sectional view of a compartmentalized filtration module of the invention, it also shows non-sectional views of a portion of the module, the views being center isometric. In these variations, the module is an example of one where the flow barrier  619  is internal to the filtrate chamber  610 .  FIG. 15  is a sectional view of the compartmentalized filtration module of the invention shown in section in  FIG. 14 . (In  FIG. 15 , the circular ring for the filter screen  617  is represented by a solid line but in fact represents a cross section of the filter screen  617 ). The filtrate chamber  610  is inside the screen  617  and the retentate chamber  645  is external to the screen; noting also that the barrier  619  is within the inner perimeter of the screen  617  and unlike the previous examples the screen filter module  605  is inverted and immersed in retentate. notwithstanding those differences, the two versions are similar in most other respects; both, filtrate and retentate chamber share a common screen wall  660 ; pump  604  which pumps filtrate reversibly into the filtrate chamber  610  which flows reversibly across the screen  617  into the retentate chamber, which retentate flows reversibly between said chamber and culture vessel through connecting conduit  603 ; noting other similar features: barrier  619 , now located within the screen  617  and within the screen filter module  605 , has a similar functions to previously ascribed to the external barrier; their function remains largely to direct fluid flow across the screen  617 ; platform  746 , which again directs filtrate flow from the filtrate chamber  610  to the retentate chamber  645 , preferably, at its more distal end from retentate chamber entrance  643 , dislodging microcarriers attached to the retentate screen wall  660  and facilitating their return to the culture vessel as before; further, openings  732  whose size and configuration may used to control the extent of filtrate flow between the distal and proximal segments, (relative to the retentate entrance  643 ), of the filtrate chamber  610 , thereby, controlling the extent of flow across different segments of the screen. Addition of air to pump chamber  608 , as previously described, generates flow from the filtrate chamber to the retentate chamber, towards the culture vessel; one such flow direction is shown by lines  671 . Exhausting chamber  608  reverses the flow direction as previously described. Means for removal of filtered harvest through the harvest port  612  is shown. The lower adapter  641  is the counterpart of upper adapters  41 ,  241  or  441  when it is used in  FIGS. 1 through 13 . Specific to  FIGS. 14 and 15  are the upper barrier surface  746 , the wires  736  which function as a stabilizing elements for the screen filter module by virtue of their attachment to base adapter  710 . 
         [0117]    Also shown in  FIGS. 14  and/or  15  are fluid connector  603 , alternating pump  604 , fluid chamber  607 , harvest port  612 , outer filtrate chamber wall  615 , upper area  618  of the screen, screen filter exit end  642 , retentate chamber entrance  643 , retentate chamber  645 , glue adhesive layer  648 , flow lines  671 , adhesive layer  726 , center post  731 , and small openings  732  (four are shown) in the barrier  619 , and bypass space  750 . 
         [0118]      FIG. 16  illustrates a filtration module  401  where the pump  404  is not directly attached to the filtration module, but which nevertheless, generates alternating flow as previously described; the alternating flow is transferred from pump into the filtration module through conduit  461 , entering the filtration module filtrate chamber  410  through the filtrate chamber entrance  478 . The flow dynamics through the filtration module remain otherwise similar to that shown in  FIGS. 11   a  and  11   b . The numbering and meaning of parts in  FIG. 16  remain essentially the same as those in  FIGS. 11   a  and  11   b . The separation of the pump from the module offers some benefits, including simplified scale up capability and the potential for greater pump flow control capability.