Production of an Alcoholic Beverage by Fermentation of Whey Permeate withKluyveromyces fragilisI: Primary Metabolism

Abstract

Whey permeate from the ultrafiltration processing of cheese manufacturing was used for alcoholic fermentation with Kluyveromyces fragilis, the objective being the production of an alcoholic beverage of low alcoholic grade. The effect of temperature, initial pH, agitation and initial biomass on yeast growth and ethanol production were assayed in batch cultures. In addition, continuous culture behaviour was studied due to interest in a continuous industrial process for a new product. An unstructured kinetic model (a Riccati kinetic equation) is proposed; batch data being employed to obtain the kinetic parameters. This model fits the continuous culture results well except for ethanol production, where calculated values were lower than experimental data. When the fermentation temperature was changed from 18 to 37°C, a maximum of YP/S close to 30°C was observed, which gives an efficiency in the conversion of lactose to ethanol of 88%. The initial pH of the whey did not affect yeast growth significantly. Experiments carried out at different initial biomass concentrations showed that an initial dry weight close to 0.5 g/litre was sufficient to carry out the fermentation. An increase in ethanol concentrations was found at higher rates of agitation. In continuous culture, a maximum productivity for biomass and ethanol was attained at a dilution rate of 0.11 h−1. Higher efficiencies (96%) were achieved in continuous culture rather than in batch cultivation mode.