Comparative Study on Two Commercial Strains ofSaccharomyces cerevisiaefor Optimum Ethanol Production on Industrial Scale

Abstract

Two commercial strains of Saccharomyces cerevisiae, Saf-Instant (Baker's yeast) and Ethanol red (Mutant) were compared for ethanol production during hot summer season, using molasses diluted up to 6-7° Brix containing 4%-5% sugars. The yeasts were propagated in fermentation vessels to study the effects of yeast cell count and varying concentrations of Urea, DAP, inoculum size and Lactrol (Antibiotic). Continuous circulation of mash was maintained for 24 hours and after this fermenter was allowed to stay for a period of 16 hours to give time for maximum conversion of sugars into ethanol. Saccharomyces cerevisiae strain (Saf-instant) with cell concentration of 400 millions/mL at molasses sugar level of 13%–15% (pH 4.6 ± 0.2, Temp. 32°C ± 1), inoculum size of 25% (v/v), urea concentration, 150 ppm, DAP, 53.4 ppm and Lactrol,150 ppm supported maximum ethanol production (8.8%) with YP/S = 250 L ethanol per tone molasses (96.5% yield), and had significantly lower concentrations of byproducts. By selecting higher ethanol yielding yeast strain and optimizing the fermentation parameters both yield and economics of the fermentation process can be improved.

Chaotropicity: a key factor in product tolerance of biofuel-producing microorganisms

“…Cellular stress mechanisms and responses, and limits for biotic activity, depend on the net effect of the prevailing factors at each time-point of the fermentation process [2 ,120]. Although the optimum temperature for S. cerevisiae metabolism and vitality is 30-358C, temperatures can sometimes reach 408C during fermentations, exacerbating the problem of product chaotropicity thereby decreasing ethanol productivity and yield [121]. The fermentation process in Brazil, the country which is most successful at commercial bioethanol production and its utilization as transport fuel, uses very high yeast cell densities in a batch or semi-continuous fed-batch mode.…”

Enrichment of protein content in cassava (Manihot esculenta Crantz) by<br>supplementing with yeast for use as animal feed

“…Ali et al (2009) showed that urea could support maximum microbial biomass protein production. Furthermore, molasses contains readily utilizable carbohydrates available in the form of fermentable sugars and can be used for yeast growth (Mukhtar et al, 2010;Polyorach et al, 2011), almost 75% of the world's molasses come from sugarcane grown in tropical climates of Asia and South America (Piggot, 2005). The process of protein enrichment of animal feed using the microorganism to improve the nutritional value of cassava has been evaluated (Oboh, 2006).…”

Enhanced Production of Bioethanol by Fermentation of Autohydrolyzed and C4mimOAc-Treated Sugarcane Bagasse Employing Various Yeast Strains

“…Cells obtained as pellet were washed twice using sterile saline (0.9% NaCl) [30], and kept in the same solution to use for further experiments. Yeast cultures were stained with methylene blue, and live cells were counted with the help of a haemocytometer [31].…”