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

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 Kluyveromyces lactis CBS2359 were performed in flasks with or without agitation to select the best conditions to produce simultaneously ethanol and biomass with high β-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 β-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 β-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.