The using of secondary raw materials as a nutrient medium for ergosterol synthesis by yeast Saccharomyces cerevisiae

Ergosterol (ergostrein), known as the precursor to vitamin D2, is widely used in various food and medical industries. The chemical synthesis of ergosterol is a complex, multi-step, and very costly process. For this reason, the industrial production of ergosterol is currently carried out by biosynthesis using various microorganisms, plant cells and microalgae. Among yeasts, Saccharomyces cerevisiae, Saccharomyces uvarum, Saccharomyces carlsbergensis, and Saccharomyces ellipsoideus are most widely used to produce ergosterol. The aim of this study was to study the intensity of ergosterol biosynthesis by two samples of Saccharomyces cerevisiae yeast using nutrient media with different glucose content (from 1 to 15 %) as the main carbon source for yeast nutrition. At the first stage of the research, the degree of yeast maturity was assessed by microscopy of a yeast preparation stained with Lugol's solution, as one of the important indicators of the technological suitability of a yeast culture for the synthesis and accumulation of ergosterol. Studies of ergosterol biosynthesis were carried out by determining its quantitative content in yeast biomass after 12, 24, 36 and 48 hours of fermentation. The results obtained showed that the nature of the process of ergosterol biosynthesis for both yeast samples was similar, and the quantitative content of glucose in the nutrient medium had a significant impact on the intensity of this process. So, the lack of glucose led to a sharp decrease in the efficiency of accumulation of ergosterol by yeast cells, after 48 hours the amount of ergosterol was 2.0-2.5 %. Excess glucose led to a significant time shift in the phase of active synthesis of ergosterol by yeast, by about 12 hours. It was found that among the studied samples, the synthesis of ergosterol proceeded most effectively when the glucose content in the nutrient medium was 8 %.