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

Wltey permeate from the ultrafiltration processing of cheese manufacturing zvas 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 groivth and ethatwl production were assayed in batch cultures.In addition, continuous culture behaviour was studied due to interest in a continuous industrial process for a nezv 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 ivas changed from 18 to 37°C, a maximum ofYPls close to 30°C was observed, ivhich gives an efficiency in the conversion of lactose to ethanol of 88%.The initial pH of the zvhey did not affect yeast groivth 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 ivas 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-\ Higher efficiencies (96%) were achieved in continuous culture rather than in batch cultivation mode.