Cheese whey permeate fermentation by <i>Kluyveromyces lactis</i>: a combined approach to wastewater treatment and bioethanol production

Abstract

Cheese whey is a dairy industry by-product responsible for serious environmental problems. Its fermentation would allow reducing its environmental impact and producing, at the same time, high-value products, hence ensuring cleaner production. Batch fermentations of cheese whey permeate, either as such or 1.5-fold or twice-concentrated, by <i>Kluyveromyces lactis</i> CBS2359 were performed in flasks with or without agitation to select the best conditions to produce simultaneously ethanol and biomass with high <i>β</i>-galactosidase activity. In shake cultures, the highest ethanol concentration (15.0 g L^-1), yield on consumed lactose (0.47 g g^-1) and productivity (0.31 g L^-1 h^-1), were obtained on cheese whey permeate as such, corresponding to 87.4% fermentation efficiency, but <i>β</i>-galactosidase activity was disappointing (449.3-680.0 U g^-1). In static cultures on twice-concentrated whey permeate, despite a decrease in fermentation efficiency and yield, ethanol production increased by 48% and <i>β</i>-galactosidase activity by no less than 209-367%. Therefore, cheese whey should be considered an alternative feedstock rather than an undesirable dairy industry by-product.