Poly(L-lactic acid) Depth Filter Membrane Prepared by Nonsolvent-Induced Phase Separation with the Aid of a Nonionic Surfactant

摘要

Poly(L-lactic acid) (PLLA) membranes prepared via a nonsolvent-induced phase separation method with a nonionic surfactant (Tween 80) have been applied as depth filters in the filtration of bacterial cell suspensions and mammalian cell broths. Finger-like pores captured the cells inside the membrane, avoiding the formation of a dense cell cake on the membrane surface. The filtration rate of lactic acid bacterial cell suspensions increased 4–5 times during depth filtration compared to that observed during screen filtration with a smooth surface. During depth filtration, the connected cellular structure as well as the finger-like pores captured the bacterial cells. The plots of the reciprocal of permeation flux vs. the permeate volume per unit filtration area suggest that capturing the bacterial cells in the pores resulted in reduced blocking constants during depth filtration compared to screen filtration. During the filtration of CHO cell broths, the cells were captured in the finger-like pores of the PLLA depth filter and on the screen filter membranes of cellulose acetate. The permeation flux was sustained at high levels for longer durations during depth filtration compared to screen filtration, although the initial flux was lower than that in screen filtration. The PLLA depth filter will be useful as a prefilter in the filtration of suspensions of compressible bacterial and mammalian cells.