Comparative Characteristics of Kluyveromyces Lactis and Kluyveromyces Marxianus Ability to Ferment Cheese Whey Into Ethanol

The purpose of this study was to find out the features of the lactose conversion into ethanol by yeast Kluyveromyces lactis and Kluyveromyces marxianus in cheese whey as a variant of environmental biotechnology under conditions of changes in the composition and properties of the culture medium. To assess the differences related to the composition and properties, we changed the pH and concentration of manganese or cobalt ions in cheese whey. The main characteristics of the process were the percentage of lactose processing, ethanol produc tion, and fermentation efficiency during 72 hours of cultivation. As a result, K. lactis Y-2037 strain decreased lactose concentration by 9.89 times within 72 hours, K. marxianus Y-2042 strain decreased it by 5.82 times. The ethanol concentration in the final medium was 20.0 g/l and 17.0 g/l, and the fermentation efficiency was 97.8% and 90.8%, respectively. A decrease in the pH of the medium to 4.2 was not accompanied by significant changes in the parameters of the biotechnological process, a further decrease in the pH to 3.9 reduced the utilization of lactose, the fermentation efficiency of K. lactis Y-2037 and K. marxianus Y-2042 decreased by 9.7% and 8.0%, respectively. An increase in the concentration of manganese ions to 25 mg/l leads to the fact that K. lactis Y-2037 and K. marxiaunus Y-2042 strains utilized 91.8% and 87.8% of lactose, forming 20.5 g/l and 18.2 g/l of ethanol, respectively. The fermentation efficiency did not change. Cobalt ions at concentrations of 1 mg/l and 2 mg/l had no effect, and cobalt ions at concentrations of 5 mg/l reduced lactose processing by the K. lactis Y-2037 strain by 1.24 times and K. marxianus Y-2042 by 1.31 times. The fermentation efficiency decreased by 1.22 times and 1.28 times, respectively. The technology of processing lactose-containing dairy industry waste by converting lactose into ethanol with K. lactis and K. marxianus yeast cultures has been proposed to be used for reducing contamination and, if necessary, for producing bioethanol internally.