Alcohol Production from Cheese Whey Permeate Using Genetically Modified Flocculent Yeast Cells

Abstract: Alcoholic fermentation of cheese whey perme-ate was investigated using a recombinant flocculating Saccharomyces cerevisiae, expressing the LAC4 (coding for b-galactosidase) and LAC12 (coding for lactose per-mease) genes of Kluyveromyces marxianus enabling for lactose metabolization. Data on yeast fermentation and growth on cheese whey permeate from a Portuguese dairy industry is presented. For cheese whey permeate having a lactose concentration of 50 gL−1, total lactose consumption was observed with a conversion yield of ethanol close to the expected theoretical value. Using a continuously operating 5.5-L bioreactor, ethanol produc-tivity near 10 g L−1 h−1 (corresponding to 0.45 h−1 dilution rate) was obtained, which raises new perspectives for the economic feasibility of whey alcoholic fermentation. The use of 2-times concentrated cheese whey permeate, cor-responding to 100 gL−1 of lactose concentration, was also considered allowing for obtaining a fermentation product with 5 % (w/v) alcohol. © 2001 John Wiley & Sons