THE COMPARATIVE STUDY ON TWO COMMERCIAL STRAINS OF SACCHAROMYCES CEREVISIAE FOR ETHANOL PRODUCTION FROM HARD-TO-FERMENT SUGAR-CONTAINING RAW MATERIALS

Abstract

The growth of bioethanol production in Ukraine is practical for both environmental and economic reasons. To reduce the cost of bioethanol production from sugar-containing raw materials, in particular, sugar beet molasses, it is effective to use high gravity wort and osmotolerant yeasts strains. Due to long exposure to high temperatures during sugar production and because of changes in the composition during storage, molasses accumulates compounds that adversely affect the function of yeast cells. For this type of raw material, a yeast strain should be found that will not only withstand high concentrations of sugars or the finished product, but will also be more resistant to inhibitors. The use of two industrial yeast strains (Deltaferm® AL-18 and Y 5007 (K-7)) for fermentation of high gravity molasses wort has been considered. It has been determined that sugar beet molasses, which is hard-to-ferment, can be used to produce ethanol from high gravity wort if some corrective measures are taken, in particular, resistant producer strains are used. It has been found that the yeast Deltaferm® AL-18 has a longer lag phase and consumes 50–60% of carbohydrates from the medium by 24 hours later than the yeast strain Y 5007 (K-7) does. It has been established how the parameters of the wash change depending on what yeast strains ferment high gravity wort based on hard-to-ferment molasses. It has been found that when using high gravity wort obtained from low-quality molasses, the yeast strain of foreign selective breeding does not allow achieving the calculated alcohol content in the fermented wash. According to the research results, under the same fermentation conditions, the distiller’s yeast strain Y 5007 (K-7) is more effective in fermenting high gravity wort based on hard-to-ferment molasses. Unlike it is with dry yeast, the industrial use of this strain according to the classical two-stream fermentation scheme does not require additional investments.