Tangential flow filtration process and apparatus

Claim 2

A multi-stage process for separating species of interest having a molecular weight of about 1 to 1000 kDa from a mixture, which process comprises: (a) filtering the mixture by tangential-flow filtration through a filtration membrane having a pore size that separates said species of interest from the mixture, while maintaining flux at a level ranging from about 5 to 100% of transition point flux in the pressure-dependent region of the flux versus TMP curve, wherein transmembrane pressure is held substantially constant along the membrane at a level no greater than the transmembrane pressure at the transition point of the filtration, whereby the species of interest are selectively separated from the mixture, and (b) filtering the filtrate from the filtration in a second tangential-flow filtration stage through a membrane having a smaller pore size than the membrane used in the first filtration stage, and recycling the filtrate of this second filtration stages back to the first filtration stage, whereby the process is repeated.

Claim 3

The process of claim 1 wherein the flux in the second filtration stage is greater than about 100% of transition point flux.

Claim 4

The process of claim 1 wherein both filtration stages are ultrafiltrations.

Claim 5

A process for separating species of interest from a mixture, which process comprises (a) filtering the mixture in a first tangential-flow filtration stage through a membrane having a pore size that separates the species of interest from the mixture, while maintaining flux at a level ranging from about 5 to 100% of transition point flux in the pressure-dependent region of the flux versus TMP curve, wherein transmembrane pressure is held substantially constant along the membrane at a level no greater than the transmembrane pressure at the transition point of the filtration, (b) filtering the filtrate from the filtration in a second tangential-flow filtration stage through a membrane having a smaller pore size than the membrane used in the first filtration stage, and (c) filtering the filtrate from the second filtration stage in a third tangential-flow filtration stage through a filtration membrane having a pore size that is less than that of the second membrane, and recycling the filtrate from the third filtration stage back to a vessel for filtration in the first filtration stage, whereby the process is repeated.

Claim 6

A process for separating species of interest from a mixture, which process comprises (a) filtering the mixture in a first tangential-flow filtration stage through a membrane having a pore size that separates the species of interest from the mixture, while maintaining flux at a level ranging from about 5 to 100% of transition point flux in the pressure-dependent region of the flux versus TMP curve, wherein transmembrane pressure is held substantially constant along the membrane at a level no greater than the transmembrane pressure at the transition point of the filtration, (b) filtering the filtrate from the filtration in a second tangential-flow filtration stage through a membrane having a smaller pore size than the membrane used in the first filtration stage, and (c) filtering the filtrate from the second filtration stage in a third tangential-flow filtration stage through a filtration membrane having a pore size that is less than that of the second membrane, and recycling the filtrate from the third filtration stage back to a vessel for filtration in the first filtration stage, whereby the process is repeated.

Claim 7

The process of claim 4 wherein the flux in the third filtration stage is greater than about 100% of transition point flux.

Claim 8

The process of claim 5 wherein all three filtration stages are ultrafiltrations.

Claim 9

A multi-stage process for separating species of interest having a molecular weight of about 1 to 1000 kDa from a mixture, which process comprises: (a) filtering the mixture by tangential-flow filtration through a filtration membrane having a pore size that separates said species of interest from the mixture, while maintaining flux at a level ranging from about 5 to 100% of transition point flux in the pressure-dependent region of the flux versus TMP curve, wherein transmembrane pressure is held substantially constant along the membrane at a level no greater than the transmembrane pressure at the transition point of the filtration, whereby the species of interest are selectively separated from the mixture, and (b) filtering the filtrate in a second tangential-flow ultrafiltration stage through an ultrafiltration membrane having smaller pore size than the membrane of the first filtration stage, and recycling the filtrate back to the first filtration stage, whereby the process is repeated.

Claim 10

A multi-stage process for separating species of interest having a molecular weight of about 1 to 1000 kDa from a mixture, which process comprises: (a) filtering the mixture by tangential-flow filtration through a filtration membrane having a pore size that separates said species of interest from the mixture, while maintaining flux at a level ranging from about 5 to 100% of transition point flux in the pressure-dependent region of the flux versus TMP curve, wherein transmembrane pressure is held substantially constant along the membrane at a level no greater than the transmembrane pressure at the transition point of the filtration, whereby the species of interest are selectively separated from the mixture, and (b) filtering the filtrate in a second tangential-flow ultrafiltration stage through an ultrafiltration membrane having smaller pore size than the membrane of the first filtration stage, and recycling the filtrate back to the first filtration stage, whereby the process is repeated.

Claim 11

A process for separating species of interest having a molecular weight of about 1 to 1000 kDa from a mixture, which process comprises: (a) filtering the mixture in a first tangential-flow filtration stage through a filtration membrane having a pore size that separates said species of interest from the mixture, while maintaining flux at a level ranging from about 5 to 100% of transition point flux in the pressure-dependent region of the flux versus TMP curve, wherein transmembrane pressure is held substantially constant along the membrane at a level no greater than the transmembrane pressure at the transition point of the filtration, whereby the species of interest are selectively separated from the mixture (b) filtering the filtrate in a second tangential-flow ultrafiltration stage through an ultrafiltration membrane having a smaller pore size than the membrane of the first filtration stage, and (c) filtering the filtrate from the second filtration stage in a third tangential-flow ultrafiltration stage through an ultrafiltration membrane having a pore size that is less than that of the second membrane, and recycling the filtrate from the third filtration stage back to a vessel for filtration in the first ultrafiltration stage, whereby the process is repeated.

Claim 12

A process for separating species of interest having a molecular weight of about 1 to 1000 kDa from a mixture, which process comprises: (a) filtering the mixture in a first tangential-flow filtration stage through a filtration membrane having a pore size that separates said species of interest from the mixture, while maintaining flux at a level ranging from about 5 to 100% of transition point flux in the pressure-dependent region of the flux versus TMP curve, wherein transmembrane pressure is held substantially constant along the membrane at a level no greater than the transmembrane pressure at the transition point of the filtration, whereby the species of interest are selectively separated from the mixture (b) filtering the filtrate in a second tangential-flow ultrafiltration stage through an ultrafiltration membrane having a smaller pore size than the membrane of the first filtration stage, and (c) filtering the filtrate from the second filtration stage in a third tangential-flow ultrafiltration stage through an ultrafiltration membrane having a pore size that is less than that of the second membrane, and recycling the filtrate from the third filtration stage back to a vessel for filtration in the first ultrafiltration stage, whereby the process is repeated.

Claim 13

A tangential-flow filtration apparatus comprising a filtration unit having a plurality of layered filtering and filtrate chambers, all but the last filtrate chamber in the layering order having inlet and outlet means each in fluid communication with a separate vessel, and the last filtrate chamber having an outlet means for circulating filtrate to the vessel that is in fluid communication with the first filtering chamber in the layering order, each chamber having a means for pumping fluid from the vessel to the inlet means of the chamber, and each chamber being separated from its adjacent chamber by a filtration membrane, the apparatus being such that the flow of fluid from the inlet to the outlet means of all chambers is parallel and in the same direction, the first filtration membrane in the layering order has a pore size that retains species of interest of the largest size, the last filtration membrane in the layering order has a pore size that retains species of interest of the least size, and the middle filtration membrane(s) in the layering order have a pore size that retains species of interest of sizes in descending order from the first to the last of the middle layered membrane(s).

Claim 14

A tangential-flow filtration apparatus comprising a filtration unit having a plurality of layered filtering and filtrate chambers, all but the last filtrate chamber in the layering order having inlet and outlet means each in fluid communication with a separate vessel, and the last filtrate chamber having an outlet means for circulating filtrate to the vessel that is in fluid communication with the first filtering chamber in the layering order, each chamber having a means for pumping fluid from the vessel to the inlet means of the chamber, and each chamber being separated from its adjacent chamber by a filtration membrane, the apparatus being such that the flow of fluid from the inlet to the outlet means of all chambers is parallel and in the same direction, the first filtration membrane in the layering order has a pore size that retains species of interest of the largest size, the last filtration membrane in the layering order has a pore size that retains species of interest of the least size, and the middle filtration membrane(s) in the layering order have a pore size that retains species of interest of sizes in descending order from the first to the last of the middle layered membrane(s).

Claim 15

The apparatus of claim 9 wherein each filtration membrane constitutes a plurality of parallel, adjacent membranes with the same pore size, one on top of the other.

Claim 16

The apparatus of claim 10 wherein each membrane constitutes two parallel, adjacent membranes, one on top of the other, with the same pore size.

Claim 17

The apparatus of claim 9 wherein the filtration unit comprises three chamber and two vessels.

Claim 18

The apparatus of claim 9 wherein the filtration unit comprises four chamber and three vessels.

Claim 19

A process for separating species of interest from a mixture comprising filtering the mixture through the apparatus of claim 9.

Claim 20

The process of claim 14 wherein the species of interest have a molecular weight of about 1 to 1000 kDa.

Claim 21

A tangential-flow filtration apparatus comprising: (a) a first vessel in fluid communication with a first filtration unit having a first filtration membrane that separates said unit into a first filtering and filtrate chamber, said filtering and filtrate chamber having an inlet and an outlet, (b) means connecting an inlet of the first filtering chamber to the first vessel, which contains means for pumping fluid from the first vessel to the inlet of the first filtering chamber, (c) means for generating a pressure gradient within the first filtrate chamber, (d) a second vessel in fluid communication with a second filtration unit having a second filtration membrane that separates said unit into a second filtering and filtrate chamber, said filtrating and filtrate chamber having an inlet and an outlet, (e) means for circulating the filtrate from the outlet of the first filtrate chamber to the second vessel, (f) means connecting an inlet of the second filtering chamber to the second vessel, which contains means for pumping fluid from the second vessel to the inlet of the second filtering chamber, (g) means for generating a pressure gradient within the second filtrate chamber, (h) a third vessel in fluid communication with a third filtration unit having a third filtration membrane that separates said unit into a third filtering and filtrate chamber, said filtering and filtrate chamber having an inlet and an outlet, (i) means for circulating the filtrate from the outlet of the second filtrate chamber to the third vessel, (j) means connecting an inlet of the third filtering chamber to the third vessel, which contains means for pumping fluid from the third vessel to the inlet of the third filtering chamber, and (k) means for circulating the filtrate from the outlet of the third filtrate chamber to the first vessel, wherein the first filtration membrane has a pore size that retains species of interest of the largest size, the second filtration membrane retains species of interest of a size intermediate to the pore size of the first and third filtration membranes, and the third filtration membrane has a pore size that retains species of interest of the smallest size.

Claim 22

A tangential-flow filtration apparatus comprising: (a) a first vessel in fluid communication with a first filtration unit having a first filtration membrane that separates said unit into a first filtering and filtrate chamber, said filtering and filtrate chamber having an inlet and an outlet, (b) means connecting an inlet of the first filtering chamber to the first vessel, which contains means for pumping fluid from the first vessel to the inlet of the first filtering chamber, (c) means for generating a pressure gradient within the first filtrate chamber, (d) a second vessel in fluid communication with a second filtration unit having a second filtration membrane that separates said unit into a second filtering and filtrate chamber, said filtrating and filtrate chamber having an inlet and an outlet, (e) means for circulating the filtrate from the outlet of the first filtrate chamber to the second vessel, (f) means connecting an inlet of the second filtering chamber to the second vessel, which contains means for pumping fluid from the second vessel to the inlet of the second filtering chamber, (g) means for generating a pressure gradient within the second filtrate chamber, (h) a third vessel in fluid communication with a third filtration unit having a third filtration membrane that separates said unit into a third filtering and filtrate chamber, said filtering and filtrate chamber having an inlet and an outlet, (i) means for circulating the filtrate from the outlet of the second filtrate chamber to the third vessel, (j) means connecting an inlet of the third filtering chamber to the third vessel, which contains means for pumping fluid from the third vessel to the inlet of the third filtering chamber, and (k) means for circulating the filtrate from the outlet of the third filtrate chamber to the first vessel, wherein the first filtration membrane has a pore size that retains species of interest of the largest size, the second filtration membrane retains species of interest of a size intermediate to the pore size of the first and third filtration membranes, and the third filtration membrane has a pore size that retains species of interest of the smallest size.

Claim 23

The apparatus of claim 16 further comprising means for generating a pressure gradient within the third filtrate chamber.

Claim 24

The apparatus of claim 16 wherein all the generating means are means for recirculating filtrate through the filtrate chamber parallel to the direction of the fluid in the filtering chamber.

Claim 25

The apparatus of claim 18 the recirculating means is a pump.

Claim 26

The apparatus of claim 16 wherein the membranes are ultrafiltration membranes of decreasing pore size in the cascade.

Claim 27

A process for separating species of interest from a mixture comprising filtering the mixture through the apparatus of claim 16.

Claim 28

The process of claim 21 wherein the species of interest have a molecular weight of about 1 to 1000 kDa.

Claim 29

A tangential-flow filtration apparatus comprising a filtration unit having two layered filtering and filtrate chambers, wherein the first filtrate chamber in the layering order has inlet and outlet means each in fluid communication with a separate vessel, and the second filtrate chamber has an outlet means for circulating filtrate to the vessel that is in fluid communication with the first filtering chamber, each chamber having a means for pumping fluid from the vessel to the inlet means of the chamber, and each chamber being separated from its adjacent chamber by filtration membrane, the apparatus being such that the flow of fluid from the inlet to the outlet means of both chambers is parallel and in the same direction, the first filtration membrane in the layering order has a pore size that retains species of interest of the largest size, and the second and last filtration membrane in the layering order has a pore size that retains species of interest of the least size.

Claim 30

A tangential-flow filtration apparatus comprising a filtration unit having two layered filtering and filtrate chambers, wherein the first filtrate chamber in the layering order has inlet and outlet means each in fluid communication with a separate vessel, and the second filtrate chamber has an outlet means for circulating filtrate to the vessel that is in fluid communication with the first filtering chamber, each chamber having a means for pumping fluid from the vessel to the inlet means of the chamber, and each chamber being separated from its adjacent chamber by filtration membrane, the apparatus being such that the flow of fluid from the inlet to the outlet means of both chambers is parallel and in the same direction, the first filtration membrane in the layering order has a pore size that retains species of interest of the largest size, and the second and last filtration membrane in the layering order has a pore size that retains species of interest of the least size.

Claim 31

A tangential-flow filtration apparatus comprising: (a) a first vessel in fluid communication with a first filtration unit having a first filtration membrane that separates said unit into a first filtering and filtrate chamber, said filtering and filtrate chamber having an inlet and an outlet, (b) means connecting an inlet of the first filtering chamber to the first vessel, which contains means for pumping fluid from the first vessel to the inlet of the first filtering chamber, (c) means for generating a pressure gradient within the first filtrate chamber, (d) a second vessel in fluid communication with a second filtration unit having a second filtration membrane that separates said unit into a second filtering and filtrate chamber, said filtrating and filtrate chamber having an inlet and an outlet, (e) means for circulating the filtrate from the outlet of the first filtrate chamber to the second vessel, (f) means connecting an inlet of the second filtering chamber to the second vessel, which contains means for pumping fluid from the second vessel to the inlet of the second filtering chamber, and (g) means for circulating the filtrate from the outlet of the second filtrate chamber to the first vessel, wherein the first filtration membrane has a pore size that retains species of interest of the largest size, and the second filtration membrane has a pore size that retains species of interest of the smallest size.

Claim 32

A tangential-flow filtration apparatus comprising: (a) a first vessel in fluid communication with a first filtration unit having a first filtration membrane that separates said unit into a first filtering and filtrate chamber, said filtering and filtrate chamber having an inlet and an outlet, (b) means connecting an inlet of the first filtering chamber to the first vessel, which contains means for pumping fluid from the first vessel to the inlet of the first filtering chamber, (c) means for generating a pressure gradient within the first filtrate chamber, (d) a second vessel in fluid communication with a second filtration unit having a second filtration membrane that separates said unit into a second filtering and filtrate chamber, said filtrating and filtrate chamber having an inlet and an outlet, (e) means for circulating the filtrate from the outlet of the first filtrate chamber to the second vessel, (f) means connecting an inlet of the second filtering chamber to the second vessel, which contains means for pumping fluid from the second vessel to the inlet of the second filtering chamber, and (g) means for circulating the filtrate from the outlet of the second filtrate chamber to the first vessel, wherein the first filtration membrane has a pore size that retains species of interest of the largest size, and the second filtration membrane has a pore size that retains species of interest of the smallest size.

Claim 33

The apparatus of claim 24 further comprising means for generating a pressure gradient within the second filtrate chamber.

Claim 34

The apparatus of claim 24 wherein the generating means are means for recirculating filtrate through the filtrate chamber parallel to the direction of the fluid in the filtering chamber.

Claim 35

The apparatus of claim 26 the recirculating means is a pump.

Claim 36

The apparatus of claim 24 wherein the membranes are ultrafiltration membranes of decreasing pore size in the cascade.

Claim 37

A multi-stage process for separating species of interest having a molecular weight of about 1 to 1000 kDa from a mixture, which process comprises: (a) filtering the mixture by tangential-flow filtration through a filtration membrane having a pore size that separates said species of interest from the mixture, while maintaining flux at a level ranging from about 5 to 100% of transition point flux in the pressure-dependent region of the flux versus TMP curve, whereby the species of interest are selectively separated from the mixture, and (b) filtering the filtrate from the filtration in a second tangential-flow filtration stage through a membrane having a smaller pore size than the membrane used in the first filtration stage, and recycling the filtrate of this second filtration stage back to the first filtration stage, whereby the process is repeated.

Claim 38

A multi-stage process for separating species of interest having a molecular weight of about 1 to 1000 kDa from a mixture, which process comprises: (a) filtering the mixture by tangential-flow filtration through a filtration membrane having a pore size that separates said species of interest from the mixture, while maintaining flux at a level ranging from about 5 to 100% of transition point flux in the pressure-dependent region of the flux versus TMP curve, whereby the species of interest are selectively separated from the mixture, and (b) filtering the filtrate from the filtration in a second tangential-flow filtration stage through a membrane having a smaller pore size than the membrane used in the first filtration stage, and recycling the filtrate of this second filtration stage back to the first filtration stage, whereby the process is repeated.

Claim 39

A process for separating species of interest from a mixture, which process comprises (a) filtering the mixture in a first tangential-flow filtration stage through a membrane having a pore size that separates the species of interest from the mixture, while maintaining flux at a level ranging from about 5 to 100% of transition point flux in the pressure-dependent region of the flux versus TMP curve, (b) filtering the filtrate from the filtration in a second tangential-flow filtration stage through a membrane having a smaller pore size than the membrane used in the first filtration stage, and (c) filtering the filtrate from the second filtration stage in a third tangential-flow filtration stage through a filtration membrane having a pore size that is less than that of the second membrane, and recycling the filtrate from the third filtration stage back to a vessel for filtration in the first filtration stage, whereby the process is repeated.

Claim 40

A process for separating species of interest from a mixture, which process comprises (a) filtering the mixture in a first tangential-flow filtration stage through a membrane having a pore size that separates the species of interest from the mixture, while maintaining flux at a level ranging from about 5 to 100% of transition point flux in the pressure-dependent region of the flux versus TMP curve, (b) filtering the filtrate from the filtration in a second tangential-flow filtration stage through a membrane having a smaller pore size than the membrane used in the first filtration stage, and (c) filtering the filtrate from the second filtration stage in a third tangential-flow filtration stage through a filtration membrane having a pore size that is less than that of the second membrane, and recycling the filtrate from the third filtration stage back to a vessel for filtration in the first filtration stage, whereby the process is repeated.

Claim 41

A multi-stage process for separating species of interest having a molecular weight of about 1 to 1000 kDa from a mixture, which process comprises: (a) filtering the mixture by tangential-flow filtration through a filtration membrane having a pore size that separates said species of interest from the mixture, while maintaining flux at a level ranging from about 5 to 100% of transition point flux in the pressure-dependent region of the flux versus TMP curve, whereby the species of interest are selectively separated from the mixture, and (b) filtering the filtrate in a second tangential-flow ultrafiltration stage through an ultrafiltration membrane having smaller pore size than the membrane of the first filtration stage, and recycling the filtrate back to the first filtration stage, whereby the process is repeated.

Claim 42

A multi-stage process for separating species of interest having a molecular weight of about 1 to 1000 kDa from a mixture, which process comprises: (a) filtering the mixture by tangential-flow filtration through a filtration membrane having a pore size that separates said species of interest from the mixture, while maintaining flux at a level ranging from about 5 to 100% of transition point flux in the pressure-dependent region of the flux versus TMP curve, whereby the species of interest are selectively separated from the mixture, and (b) filtering the filtrate in a second tangential-flow ultrafiltration stage through an ultrafiltration membrane having smaller pore size than the membrane of the first filtration stage, and recycling the filtrate back to the first filtration stage, whereby the process is repeated.

Claim 43

A process for separating species of interest having a molecular weight of about 1 to 1000 kDa from a mixture, which process comprises: (a) filtering the mixture in a first tangential-flow filtration stage through a filtration membrane having a pore size that separates said species of interest from the mixture, while maintaining flux at a level ranging from about 5 to 100% of transition point flux in the pressure-dependent region of the flux versus TMP curve, whereby the species of interest are selectively separated from the mixture (b) filtering the filtrate in a second tangential-flow ultrafiltration stage through an ultrafiltration membrane having a smaller pore size than the membrane of the first filtration stage, and (c) filtering the filtrate from the second filtration stage in a third tangential-flow ultrafiltration stage through an ultrafiltration membrane having a pore size that is less than that of the second membrane, and recycling the filtrate from the third filtration stage back to a vessel for filtration in the first ultrafiltration stage, whereby the process is repeated.

Claim 44

A process for separating species of interest having a molecular weight of about 1 to 1000 kDa from a mixture, which process comprises: (a) filtering the mixture in a first tangential-flow filtration stage through a filtration membrane having a pore size that separates said species of interest from the mixture, while maintaining flux at a level ranging from about 5 to 100% of transition point flux in the pressure-dependent region of the flux versus TMP curve, whereby the species of interest are selectively separated from the mixture (b) filtering the filtrate in a second tangential-flow ultrafiltration stage through an ultrafiltration membrane having a smaller pore size than the membrane of the first filtration stage, and (c) filtering the filtrate from the second filtration stage in a third tangential-flow ultrafiltration stage through an ultrafiltration membrane having a pore size that is less than that of the second membrane, and recycling the filtrate from the third filtration stage back to a vessel for filtration in the first ultrafiltration stage, whereby the process is repeated.