BIOTECHNOLOGY OF ALCOHOLIC FERMENTATION WITH YEAST RECIRCULATION

Abstract

In recent decades, there has been a tendency in the world to increase ethanol production significantly in order to solve energy problems, that is, to use it as a biofuel. The factors determining the production cost of targeted biotechnological products include the output of these products from the raw materials used. One of the modern and effective ways to intensify alcoholic fermentation and reduce the cost of fuel ethanol is yeast recirculation. The research objects were: raw material (sugarbeet molasses), molasses wort, yeast Saccharomyces cerevisiae of the strain M-5, fermented wash and its distillates. In the raw materials, intermediate products, and fermented wash, the techno-chemical parameters recommended by the current technology regulations for obtaining spirit from molasses have been determined. Acoholic fermentation was carried out in an industrial environment, in a battery of series-connected fermentors. Recirculation of yeast was carried out by separating it from the final stage of fermentation, concentrating it on the separator, and introducing it into the first fermentor. The experimental data obtained prove that for wort fermentation, it is effective to use yeast that recirculates in the anaerobic stage. It has been established that the alcohol-forming power of recycled yeast increases as the yeast adapts to the environment in which it has been staying for a long time. The yeast becomes more active biochemically, with more efficient metabolism. Its need for continuously cultured biomass is reduced, the share of aerobically assimiliated sugars decreases, and, consequently, the losses during yeast generation are fewer. At the same time, accelerating the initial period of anaerobic fermentation helps inhibit the biosynthesis of glycerol, the formation of which consumes the largest amount of sugar among all the secondary products. The parameters of molasses wort fermentation, with yeast biomass recirculating, have been determined in an industrial environment. It has been established that the alcohol output from the raw materials increases as the synthesis of secondary metabolic products weakens. The advantages of this fermentation method will be used in further studies, namely when fermenting molasses wort, with an increased concentration of dry matter, in order to reduce the specific heat energy consumption in production and to make it cheaper. The developed biotechnology of alcohol can be usefully employed to produce fuel ethanol, and increasing its production will contribute to Ukraine’s energy self-sufficience.