초록
Experimental investigation on cross-flow and pressure ultrafiltration (UF) fermentation broth of lactic acid during the whey fermentation using a bioreactor equipped with zirconium oxide stainless steel (ZOSS) membrane was carried out. Different filtration resistance (R<SUB>f</SUB> and R<SUB>i</SUB>) components were calculated to understand better the interactions between the membrane and fermentation feed. Various raw materials (deproteinated synthetic whey S1, model/synthetic whey S2 and ultrafiltration dairy whey permeate S3) were used as a feed for UF tests under constant conditions. It was found that the highest concentration of lactic acid in permeate (0.69+/-0.95%wt.) as well as permeate flux (0.5+/-5.5.10<SUP>-6</SUP>m<SUP>3</SUP>m<SUP>-2</SUP>s<SUP>-1</SUP>) was obtained with the transmembrane pressure of 2.10<SUP>6</SUP>Pa and the cross-flow velocity of 1ms<SUP>-1</SUP>. Under these conditions the fouling resistance of 6.87.10<SUP>11</SUP>m<SUP>-1</SUP> was minimal. The integration of bioreactor with ZOSS membranes seems to be promising concept in the production and filtration of lactic acid in the dairy industry.