Abstract
Two yeast isolates of C.kefyr-T and C.kefyr-S, were isolated from crude whey, the optimum pH value was 5, and S.cerevisiae was significantly best in ethanol and Biomass production from all glucose concentrations compared to C.kefyr-T and C.kefyr-S which were significantly best ethanol and biomass production from all galactose concentrations comparing with S.cerevisiae. C.kefyr-T which was best in production compared to C.kefyr-S. Best ethanol production was 8.7% Ethanol from 10% sugar mixture, by mixed culture of (S. cerevisiae+ C.Kefyr-T), and best ethanol production was 4.6% from 8% synthetic lactose by mixed culture of (C.kefyr-T+C.kefyr-S). There is a significant decrease in ethanol and biomass production from all mixtures by using mixed culture of (C.kefyr-T+ C.kefyr-S+ S. cerevisiae) than using mixed culture of (C. kefyr + S. cerevisiae) and mixed culture of (C.kefyr-T + C.kefyr-S). Different period of times at (24, 36, 48, and 60) hof fermentation in bioreactor are presented. The initial sugar mixture concentration was 10% in all cases. The ethanol production during the 48 h gave a maximum value of 15.5 % by mixed culture of (C. kefyr + S. cerevisiae), but it remains at low levels within other periods, whereas the highest biomass16% gained at the same bioreactor conditions.
Highlights
Alternative fuels are important for the world to reduce their dependence on fossil fuels
Results & Discussion Figures (1: A-F) to (2: A-F) indicate to presence of relationship between sugar concentration and pH values in Ethanol and Biomass production from individual sugar by individual yeast (S.cerevisiae, C.kefy-T, C.kefyr-S), the production of ethanol and biomass were gradually increased with increasing of sugar concentrations in media, under constant pH value, and the best production was at pH=5, in agreement with [16] who found relationship between sugar and (H+) concentrations in ethanol production from by S. cerevisiae, and pH(5, 5.5) were the best values for production
At constant sugar concentration there was no significant differences in ethanol, biomass production at pH (4-6) values, and the best production was at pH average 5.0. This result was similar to those of [17], who found no high significant differences in ethanol production from (Helianthus tuberosus) plant by S. cerevisiae at (4.5-6.0) pH values, under constant sugar concentration, and the best production was at pH5
Summary
Alternative fuels are important for the world to reduce their dependence on fossil fuels. The industrial importance of yeast are: their ability to ferment wide range of sugar for, ethanol, single cell protein (feed source for human and animal), enzymes, fats, and vitamins production [6]. Different concentrations (2,4,6,8,10,12,14)% of glucose were prepared, by disolving different grams of this sugar in (100)ml of synthetic medium in (1000) ml of D.W according to[12] They Justified at different (3, 4,5,6,7) pH values and sterilized by autoclave under 15 psig at 121ْC for 15 minutes. Different concentration (2,4,6,8,10,12,14) % of equal ratio (glucose & galactose) mixture were prepared, justified at pH=5, each seven different concentrations were inoculated by one type of yeast inoculums, incubated as above. Mixed sugar were prepared and pH values were justified as above, each concentration was inoculated by mixed yeast culture (S.cerevisiae + C. kefyr-T) or (S.cerevisiae + C.kefyr-S) or (C.kefyr-T + C.kefyr-S) or (S. cerevisiae+ C.kefyr-T+C. kefyr- S), incubated as the same condition above
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