Characteristics of different brewer’s yeast strains used for non-alcoholic beverage fermentation in media containing different fermentable sugars (original) (raw)
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Proceeding of the 2nd International Seminar on Chemistry, 2011
High sugar concentration is more preferred in industrial bioethanol production, as it can increase the amount of ethanol produced by the end of fermentation. However, when high sugar concentration is used in the media, yeast cells are exposed to high osmotic stress, which can affect the fermentation performance. The present experiment aimed to investigate the fermentation performance of the yeast S. cerevisiae at high sugar concentration, in poor (Yeast nitrogen base/YNB) and rich (yeast extract peptone/YEP) media. Growth parameters and sugar utilization were monitored during the fermentations. The results indicate that all three strains used had stuck fermentations, leaving 50 to 60% residual sugar. Therefore, a follow up experiment was conducted by using media of different nutritional value, including YNB with nitrogen supplementation and YEP, as well as different sugars (sucrose or glucose). Yeast cell grown in YEP had better fermentation performance indicated by higher sugar utilization. Addition of ammonium sulphate to YNB media did not change fermentation performance of the yeast cells. In YEP media, cells grown with glucose tended to maintain better viability than sucrose. Our study confirmed that nutrient availability is very important for fermentation performance. Comparison of YNB and YEP media indicates that nutritionally insufficient media are not suitable for high concentration sugar fermentation.
Research Article, 2013
Two ethanol fermenting Saccharomyces cerevisiae were isolated from date juice and grapes and grown in YEPD medium. They were characterized for alcoholic fermentation using sugarcane molasses and their growth conditions were optimized with respect to pH and sugar concentration. Results revealed a temperature of 30ºC, pH 6.0 and 6.5% sugar concentration as optimum for fermentation. Stress tolerance tests showed that date juice isolate was highly tolerant to temperature, pH and high ethanol concentration in the medium. Under optimized conditions, S. cerevisiaeisolated from date-juice produced 7.75% of ethanol in molasses as estimated by Conway method.
Alcoholic Fermentation Rate by Saccharomyces cerevisiae Utilizing Sucrose Versus Glucose
Metabolism can be defined as the chemical reactions occurring in a cell. Glucose metabolism and sucrose metabolism refer to the chemical reactions needed for the breakdown of glucose or the chemical reactions needed for breakdown of sucrose. This breakdown provides the cell with energy for biological processes. We evaluated the rates of alcoholic fermentation by comparing sucrose and glucose using Saccharomyces cerevisiae in order to determine which fermented the greatest. We hypothesized that the rate of fermentation would by greater in glucose than in sucrose because sucrose is a disaccharide with the composition of glucose and fructose while glucose is a monosaccharide. In test tubes containing a total volume of 24 ml with part buffer, glucose or sucrose solution and Saccharomyces cerevisiae suspension we observed that the rate of fermentation at 30 minutes of sucrose had no significant difference than the rate of alcoholic fermentation at 30 minutes of glucose.