Optimization of baker`s yeast production on grape juice using response surface methodology

Abstract

There is an increasing interest in improving biological processes, including fermentation processes, improving fermentation conditions is difficult, as it requires the use of an appropriate improvement method that allows operating the biological fermenter under optimal conditions in order to obtain the largest possible amount of the final product. The aim of this work was to succeed in examples of fermentation conditions to produce the largest possible quantity of dry yeast biomass Saccharomyces cerevisiae using grape juice as the sole carbon source. The optimum values of five factors that have an effect on the production of dry biomass from baker`s yeast were determined. The design of the experiments was carried out using the central composite experimental design (CCD) and the number of experiments according to the design was (54) experiments, the response surface methodology method was used to determine the best possible amount of production of yeast, and has reached (41.44 g/L) after 12 hours of fermentation, under the following optimal conditions (temperature (30.11??), pH (4.75), sugar concentration (158.36 g/L), the ratio of carbon to nitrogen (an essential nutrient for yeast growth ) is (11.9), initial concentration of yeasts (2.5 g/L), the amount of urea was 6.65 g/L and the amount of ammonium sulfate used was 6.65 g/L, so that the concentration of added urea and ammonium sulfate was (50-50)% and the required C/N ratio was achieved, and the used agitation speed was equal to 200 r.p.m during the fermentation process. The fermenter power of the obtained yeast was 470 ml. Three kinematic models (Monod, Verhulst, and Tessier) were also selected for the purpose of studying the kinetic performance of Saccharomyces cerevisiae yeast. Monod and Tessier`s models did not give satisfactory results, while the best results were according to the Verhulst model. Also, the Leudeking Piret model has also been successfully used to predict substrate consumption during fermentation time.