An optimal medium （300 g·L^-1 initial glucose） comprising 6.3 mmol·L^-1 Mg2＋, 5.0 mmol·L^-1 Ca2＋, 15.0 g·L^-1 peptone and 21.5 g·L^-1 yeast extract was determined by uniform design to impr...An optimal medium （300 g·L^-1 initial glucose） comprising 6.3 mmol·L^-1 Mg2＋, 5.0 mmol·L^-1 Ca2＋, 15.0 g·L^-1 peptone and 21.5 g·L^-1 yeast extract was determined by uniform design to improve very high gravity （VHG） ethanol fermentation, showing over 30% increase in final ethanol （from 13.1% to 17.1%, by volume）, 29% decrease in fermentation time （from 84 to 60 h）, 80% increase in biomass formation and 26% increase in glucose utilization. Experiments also revealed physiological aspects linked to the fermentation enhancements. Compared to the control, trehalose in the cells grown in optimal fermentation medium increased 17.9-, 2.8-, 1.9-, 1.8- and 1.9-fold at the fermentation time of 12, 24, 36, 48 and 60 h, respectively. Its sharp rise at the early stage of fermentation when there was a considerable osmotic stress suggested that trehalose played an important role in promoting fermentation. Meanwhile, at the identical five fermentation time, the plasma membrane ATPase activity of the cells grown in optimal medium was 2.3, 1.8, 1.6, 1.5 and 1.3 times that of the control, respectively. Their disparities in enzymatic activity became wider when the glucose levels were dramatically changed for ethanol production, suggesting this enzyme also contributed to the fermentation improvements. Thus, medium optimization for VHG ethanol fermentation was found to trigger the increased yeast trehalose accumulation and plasma membrane ATPase activity.展开更多
This study optimized ethanol production from sweet sorghum stem juice(SSJ)by Saccharomyces cerevisiae NP01 under very high gravity(VHG)fermentation in 500-mL air-locked flasks at 30℃.Response surface methodology base...This study optimized ethanol production from sweet sorghum stem juice(SSJ)by Saccharomyces cerevisiae NP01 under very high gravity(VHG)fermentation in 500-mL air-locked flasks at 30℃.Response surface methodology based on a Box-Behnken design was employed to optimize initial sugar(267 g/L),urea(3.24 g/L),and cell concentration(1.32×10^(8) cells/mL)for maximization of ethanol concentration(PE),productivity(QP),and sugar consumption(%SC).The experimental values(PE,119.29 g/L;QP,2.49 g/L.h and%SC,91.83%)under optimal conditions were close to the predicted values,verifying the optimization process.Aeration(2.5 vvm for 4 h)increased viable cell counts and decreased glycerol production(a by-product),but not fermentation efficiency.An osmoprotectant(40 mM potassium chloride combined with 10 mM potassium hydroxide,KCl/KOH)at 30℃ had no positive effect on ethanol fermentation efficiency.However,at 25℃,the osmoprotectant increased PE from 106 to 116 g/L and ethanol yield from 0.46 to 0.49 g/g.At 35-37℃,it prolonged cell viability,increasing PE by 5-12 g/L and%SC by 3-8%without affecting ethanol yield.However,at 39℃,no positive impact occurred on ethanol fermentation efficiency.The findings from this study,particularly the optimized fermentation conditions and stress tolerance strategies,could guide the scale-up to an industrial level of bioethanol production from sweet sorghum stem juice or other feedstocks using VHG fermentation,contributing to the development of more efficient and sustainable biofuel production processes.展开更多
Background:The energy crisis and climate change necessitate studying and discovering of new processes involved in the production of alternative and renewable energy sources.Very high gravity(VHG)fermentation is one su...Background:The energy crisis and climate change necessitate studying and discovering of new processes involved in the production of alternative and renewable energy sources.Very high gravity(VHG)fermentation is one such process improvement aimed at increasing both the rate of fermentation and ethanol concentration.The technology involves preparation and fermentation of media containing 300 g or more of dissolved solids per liter to get a high amount of ethanol.Findings:Saccharomyces cerevisiae was inoculated to the very high gravity medium containing 30%to 40%w/v glucose with and without supplementation of three selected fruit pulps(mango,banana,and sapota).The fermentation experiments were carried out in batch mode.The effect of supplementation of 4%fruit pulp/puree on the metabolic behavior and viability of yeast was studied.Significant increase in ethanol yields up to 83.1%and dramatic decrease in glycerol up to 35%and trehalose production up to 100%were observed in the presence of fruit pulp.The fermentation rate was increased,and time to produce maximum ethanol was decreased from 5 to 3 days with increased viable cell count.The physical and chemical factors of fruit pulps may aid in reducing the osmotic stress of high gravity fermentation as well as enhanced ethanol yield.Conclusions:It was found that fruit pulp supplementation not only reduced fermentation time but also enhanced ethanol production by better utilization of sugar.Production of high ethanol concentration by the supplementation of cheap materials in VHG sugar fermentation will eliminate the expensive steps in the conventional process and save time.展开更多
基金Supported by the Natural Science Foundation of Fujian Province of China （E0810018）
文摘An optimal medium （300 g·L^-1 initial glucose） comprising 6.3 mmol·L^-1 Mg2＋, 5.0 mmol·L^-1 Ca2＋, 15.0 g·L^-1 peptone and 21.5 g·L^-1 yeast extract was determined by uniform design to improve very high gravity （VHG） ethanol fermentation, showing over 30% increase in final ethanol （from 13.1% to 17.1%, by volume）, 29% decrease in fermentation time （from 84 to 60 h）, 80% increase in biomass formation and 26% increase in glucose utilization. Experiments also revealed physiological aspects linked to the fermentation enhancements. Compared to the control, trehalose in the cells grown in optimal fermentation medium increased 17.9-, 2.8-, 1.9-, 1.8- and 1.9-fold at the fermentation time of 12, 24, 36, 48 and 60 h, respectively. Its sharp rise at the early stage of fermentation when there was a considerable osmotic stress suggested that trehalose played an important role in promoting fermentation. Meanwhile, at the identical five fermentation time, the plasma membrane ATPase activity of the cells grown in optimal medium was 2.3, 1.8, 1.6, 1.5 and 1.3 times that of the control, respectively. Their disparities in enzymatic activity became wider when the glucose levels were dramatically changed for ethanol production, suggesting this enzyme also contributed to the fermentation improvements. Thus, medium optimization for VHG ethanol fermentation was found to trigger the increased yeast trehalose accumulation and plasma membrane ATPase activity.
基金supported by the Graduate School,Khon Kaen University,Thailand(Research Fund for Supporting Lecturer to Admit High Potential Student to Study and Research on His Expert Program Year 2020,Grant number 631 T104)Fermentation Research Center for Value Added Agricultural Products(FerVAAP),Khon Kaen University,Thailand。
文摘This study optimized ethanol production from sweet sorghum stem juice(SSJ)by Saccharomyces cerevisiae NP01 under very high gravity(VHG)fermentation in 500-mL air-locked flasks at 30℃.Response surface methodology based on a Box-Behnken design was employed to optimize initial sugar(267 g/L),urea(3.24 g/L),and cell concentration(1.32×10^(8) cells/mL)for maximization of ethanol concentration(PE),productivity(QP),and sugar consumption(%SC).The experimental values(PE,119.29 g/L;QP,2.49 g/L.h and%SC,91.83%)under optimal conditions were close to the predicted values,verifying the optimization process.Aeration(2.5 vvm for 4 h)increased viable cell counts and decreased glycerol production(a by-product),but not fermentation efficiency.An osmoprotectant(40 mM potassium chloride combined with 10 mM potassium hydroxide,KCl/KOH)at 30℃ had no positive effect on ethanol fermentation efficiency.However,at 25℃,the osmoprotectant increased PE from 106 to 116 g/L and ethanol yield from 0.46 to 0.49 g/g.At 35-37℃,it prolonged cell viability,increasing PE by 5-12 g/L and%SC by 3-8%without affecting ethanol yield.However,at 39℃,no positive impact occurred on ethanol fermentation efficiency.The findings from this study,particularly the optimized fermentation conditions and stress tolerance strategies,could guide the scale-up to an industrial level of bioethanol production from sweet sorghum stem juice or other feedstocks using VHG fermentation,contributing to the development of more efficient and sustainable biofuel production processes.
基金financial support given in the form of research projects entitled‘Studies on Rapid and Enhanced Production of Ethanol through Very High Gravity(VHG)Fermentation’(Ref No:38(1310)/11/EMR-II)‘Biotechnological production of Acetone-Butanol-Ethanol(ABE)from agricultural biomass using solventogenic bacteria’(Ref No:SR/FT/LS-79/2009).
文摘Background:The energy crisis and climate change necessitate studying and discovering of new processes involved in the production of alternative and renewable energy sources.Very high gravity(VHG)fermentation is one such process improvement aimed at increasing both the rate of fermentation and ethanol concentration.The technology involves preparation and fermentation of media containing 300 g or more of dissolved solids per liter to get a high amount of ethanol.Findings:Saccharomyces cerevisiae was inoculated to the very high gravity medium containing 30%to 40%w/v glucose with and without supplementation of three selected fruit pulps(mango,banana,and sapota).The fermentation experiments were carried out in batch mode.The effect of supplementation of 4%fruit pulp/puree on the metabolic behavior and viability of yeast was studied.Significant increase in ethanol yields up to 83.1%and dramatic decrease in glycerol up to 35%and trehalose production up to 100%were observed in the presence of fruit pulp.The fermentation rate was increased,and time to produce maximum ethanol was decreased from 5 to 3 days with increased viable cell count.The physical and chemical factors of fruit pulps may aid in reducing the osmotic stress of high gravity fermentation as well as enhanced ethanol yield.Conclusions:It was found that fruit pulp supplementation not only reduced fermentation time but also enhanced ethanol production by better utilization of sugar.Production of high ethanol concentration by the supplementation of cheap materials in VHG sugar fermentation will eliminate the expensive steps in the conventional process and save time.
