Ethanol yield optimization of the synthetic glucose-ammonium medium composition for the Saccharomyces cerevisiae Y-1693 strain

One of the ways of processing unconventional non-wood plant raw materials is production of bioethanol. Since hydrolyzates are media that are hardly suitable for yeast life activity due to insufficient content of nitric and phosphoric compounds, nutrient salts must be additionally introduced into media compositions at an optimum quantity. The work is aimed at studying nutrient demands of Saccharomyces сerevisiae (Y-1693 strain) saccharomycetes and optimizing the synthetic glucose-ammonium medium composition by ethanol yield.Three parameters were varied in the experiments: glucose level, monosubstituted potassium phosphate concentration, and ammonium sulphate concentration. The dependence of the metabolism product accumulation, ethanol, by Saccharomyces сerevisiae strain Y-1693 on the synthetic glucose-ammonium medium composition was consequently demonstrated. To reveal the mutual influence between those parameters using Math CAD software, a regression equation was formulated. By the least square method, the regression equation coefficients were computed. Using the regression equation, a function graph for the desired product yield (ethanol) was plotted which corresponds to the ethanol yield of 95% of the theoretical one and represents a surface. The adequacy of the constructed regression equation has been validated in practice by conducting three more experiments and calculating the Fischer's criterion. The regression equation has been found to describe adequately the experiment with 95% confidence. The recommended concentrations of monosubstituted potassium phosphate and ammonium sulphate which should be added to the medium with the known glucose level were calculated by the formulated equation. The results obtained on model glucose-ammonium media will be exploited to optimize the composition of nutrient media based on hydrolyzates of non-traditional non-wood plant raw materials.

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