Separation of protein from suspended particles using submerged membrane filtration

In this study, bovine serum albumin (BSA) molecules are separated from suspended particles using submerged membrane filtration. Several methods, including constant-pressure filtration with backwash, air bubble sparging and a stepwise increase in pressure, are used to reduce filtration resistance and to enhance filtration flux. The effects of filtration pressure, backwash flow rate, backwash duration, air flow rate and stepwise pressure increase on filtration flux, filtration resistances, BSA rejection and BSA production are discussed. The results show that internal fouling of the filter membrane is the most important contributor to the overall filtration resistance, while cake formation is the main determinant of BSA rejection. An increase in filtration pressure leads to lower filtration flux and lower BSA rejection due to more severe internal fouling of the membrane. Although additional periodic backwash or air bubble sparging increases the filtration flux relative to solely constant-pressure filtration, the filtration flux and BSA production when using a stepwise pressure increase is much higher than with the other operations, especially when the latter is combined with a periodic backwash. Moreover, the calculated filtration flux and BSA rejection results for constant-pressure filtration under various filtration pressures agree fairly well with experimental data.

Research highlights▶ To increase protein recovery by considering both filtration flux and protein rejection is an important issue in membrane bio-separation processes. ▶ The main purpose of this study is to understand how to enhance the filtration flux and protein recovery in submerged membrane filtration by using hydrodynamic methods. ▶ PMMA particles and BSA were selected as the sample cells and proteins, respectively. ▶ A low BSA rejection membrane was selected to increase the BSA transmission; however, the depositions of PMMA particles on and in the membrane resulted in significant filtration resistances. ▶ Therefore, to increase filtration flux and simultaneously maintain high BSA transmission was a clear goal of this study. ▶ Several hydrodynamic operating conditions, including constant-pressure filtration, air bubble sparging, periodic backwash and a stepwise increase in filtration pressure, were used for reducing membrane fouling, enhancing the permeating flux and increasing the BSA production. ▶ The effects of these operations on the filtration resistances, filtration fluxes and BSA rejection were thoroughly discussed.