The use of apple cake extracts for the intensification of ergosterol biosynthesis

The purpose of this study was to study the possibility of using secondary resources for processing apple raw materials in the technology of yeast biosynthesis of ergosterol. Ergosterol is produced on an industrial scale by microbiological synthesis. To increase the efficiency of this process, various approaches are used, including variations of the nutrient media used for yeast cultivation. In the present study, an extract obtained from the waste products of apple juice production was used as a nutrient medium. It was found that apple cake made up more than 70 % of all waste in the production of direct-pressed juice. To intensify the process of extracting valuable components from apple cake, low-frequency ultrasonic exposure was applied in the processing mode of 189 W and 5 min. Two samples of Saccharomyces yeast were selected for the study: dry baking yeast and dry wine yeast. As part of the study, a conditional assessment of the maturity and physiological state of yeast was carried out, which confirmed the possibility of their use for biosynthesis technologies. To assess the potential applicability of apple cake extract as a nutrient medium for yeast cultivation, its chemical composition was determined and the titratable acidity value was determined. The results showed a sufficient amount of sugars for the technology of ergosterol synthesis (9.3 %) and an acceptable value of titratable acidity (1.4 %). The effectiveness of ergosterol biosynthesis by yeast on the extract was evaluated in comparison with the control nutrient medium - YP with the addition of glucose. The results of the determination of the ergosterol content after cultivation showed that, regardless of the type of yeast used, the amount of ergosterol was higher when the yeast was cultured on apple cake extracts. At the same time, for baking yeast, the increase was more than 200 % in comparison with the control.