Selection of Yeast Strain Kluyveromyces marxianus for Alcohol and Biomass Production on Whey

S. Grba, V. Stehlik-Tomas, D. Stanzer, N. Vahčić and A. Škrlin

Abstract
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 30 °C, 34 °C and 37 °C, 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, 34 °C 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 34 °C 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 ϕ = 7,31 %. The results achieved in all experiments showed that the selected yeast strains, K. marxianus VST 44 and ZIM 75, could be succesfully used in the ethanol and yeast biomass production on whey.

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Keywords
Kluyveromyces marxianus, whey, fermentation, ethanol, biomass, cultivation conditions