Selection of yeast strain Kluyveromyces marxianus for alcohol and biomass production on whey

This paper emphasizes the suitability of five different strains of yeast Kluyveromyces marxianus for alcoholic fermentation on deproteinized whey. The selection of yeast strains was performed at different cultivation conditions: temperatures were 30degreesC, 34degreesC and 37degreesC, respectively, and the concentration of lactose in the substrate varied from 5% to 15%. Cultivations were carried out in aerobic conditions on a rotary shaker, at pH 4.5-5.0. During cultivations the kinetics of alcoholic fermentations was analysed. Satisfactory results were achieved almost with all the yeast strains, but the best results were gained with K. marxianus VST 44 and ZIM 75, respectively. On the other hand, 34degreesC seemed to be the optimal temperature for both strains. To optimize the process fed-batch cultivations were performed with the chosen strains of K. marxianus at 34degreesC in aerobic/anaerobic conditions. The process ended after 12-14 hours. At the end of the process the biomass yield reached 10 g L-1 and the ethanol fraction was phi=7.31%. The results achieved in all experiments showed that the selected yeast strains, K. marxianus VST 44 and ZIM 75, could be successfully used in the ethanol and yeast biomass production on whey.