Improvement of Ethanol Production Using Saccharomyces cerevisiae by Enhancement of Biomass and Nutrient Supplementation

Abstract

Optimization of ethanol production through addition of substratum and protein-lipid additives was studied. Oilseed meal extract was used as protein lipid supplement, while rice husk was used as substratum. The effect of oil seed meal extract and rice husk was observed at varying concentration of medium sugar from 8% to 20%. Of the three oil seed meal extracts used, viz. groundnut, safflower, and sunflower, safflower was found to be most efficient. The use of oilseed meal extract at 4% was found to enhance ethanol production by almost 50% and enhanced sugar tolerance from 8% to 16%. A further increase of almost 48% ethanol was observed on addition of 2 g of rice husk per 100 ml of medium. An increase in cell mass with better sugar attenuation was observed. Further optimization was sought through use of sugarcane juice as the sugar source. While 8.9% ethanol yield with 75% sugar attenuation was observed at 20% sucrose concentration, it was found to increase to 12% (v/v) with almost complete utilization of medium sugar when sugarcane juice was used. Cell weight was also observed to increase by 26%.

Current Trends in Bioethanol Production by Saccharomyces cerevisiae: Substrate, Inhibitor Reduction, Growth Variables, Coculture, and Immobilization

“…The supplementation of exogenous nitrogen sources such as yeast extract, malt extract, peptone, and (NH 4 ) 2 SO 4 to the natural growing media enhanced ethanol production in S. cerevisiae [ 49 , 51 ]. Supplements also enhance sugar utilization [ 19 , 40 , 49 , 51 , 69 ] which might be one reason for better ethanol yield with supplemented substrates. One reason for enhanced ethanol production with yeast extract supplementation was the presence of important cofactors like biotin and riboflavin [ 40 ].…”

“…Like [ 19 , 49 ], higher ethanol yield could be obtained from the addition of vitamins, amino acids, sterols, or yeast extract [ 69 ]. However, these supplements are too expensive to use at industrial level and hence cheap additives such as sunflower, groundnut, and safflower oilseed meal cakes, wheat mash, or soy flour could be used.…”

Effects of soy protein hydrolysates on the growth and fermentation performances of brewer's yeast

“…Nitrogen source plays an important role in yeast growth and product formation. In traditional beer brewing, free amino nitrogen, constituted by amino acids, ammonium ions and small peptides in wort, is utilised as a nitrogen source and has been proved to ensure efficient yeast cell growth and hence desirable fermentation performance (Sankh et al, 2011). The importance of free amino nitrogen in wort for brewery fermentation has been studied for many years (Jones & Pierce, 1964;Perp ete et al, 2005).…”

Strain improvement of industrially important microorganisms based on resistance to toxic metabolites and abiotic stress

“…It is well known that polyunsaturated oils and unsaturated fatty acids present in safflower oilseed play a great role in ethanol tolerance . Similarly, supplementation of safflower oilseed meal (4%) enhanced the ethanol production by 50% and the sugar tolerance was improved from 8 to 16%; the addition of 2% rice husk also raised the ethanol amount by 48% . This might lead to a conclusion that some sort of nutrients present in safflower might influence yeast metabolism toward higher ethanol yield.…”

“…It can be done by supplementation of fermentation broth with a source of unsaturated lipids, and alternatively by medium aeration to stimulate lipid biosynthesis . A significant increase in the ethanol content was obtained in all supplemented media in safflower oil seed meals compared to an unsupplemented one . It is well known that polyunsaturated oils and unsaturated fatty acids present in safflower oilseed play a great role in ethanol tolerance .…”