Modeling the influence of slurry concentration on Saccharomyces cerevisiae cake porosity and resistance during microfiltration

Abstract

Filtration of an isotonic suspension of baker's yeast through a 0.45-μm membrane was studied at two different pressures, 40 and 80 kPa, for yeast concentrations ranging from 0.14 to 51 kg/m(3) (dry weight). For a yeast volume fraction above 0.06 (~21.8 kg/m(3) ), the porosity of the yeast cake is less dependent on the suspension concentration. For highly diluted suspensions, the specific cake resistance approaches a minimum that depends on the filtration pressure. Correlation functions of cake porosity and specific cake resistance were obtained for the concentration range investigated showing that the Kozeny-Carman coefficient increases when the applied pressure increases. Both filtration pressure and slurry concentration can be process controlled. In the range of moderate yeast concentration, the filtrate flux may be increased by manipulating the filtration pressure and the slurry concentration, thereby improving the overall process efficiency. The complex behavior of yeast cakes at high slurry concentration can be described by a conventional model as long as part of yeast cells are assumed to form aggregates, which behave as single bigger particles. The aggregation effect may be accounted for using a binary mixture model.

Comparison of Polypropylene and Ceramic Microfiltration Membranes Applied for Separation of 1,3-PD Fermentation Broths and Saccharomyces cerevisiae Yeast Suspensions

“…Microfiltration (MF) is one of the oldest membrane technologies [1], which is characterized by operating pressure lower than 0.35 MPa and high permeate fluxes, mainly between 10 −4 and 10 −2 m/s [2]. Over the last two decades, many attempts have been made by researchers to comprehensively investigate the use of MF in the clarification of fermentation broths [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] and yeast suspensions [19][20][21][22][23][24][25][26][27][28][29][30][31][32]. It is due to the fact that separation of biological materials using conventional centrifugal methods is difficult and expensive [33].…”