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
In this paper, a study of the bifurcation analysis of fermentation of sugar to ethanol in presence of Saccharomyces cerivisiae at very high gravity is described. The bifurcation analysis was done for a concentration 2...In this paper, a study of the bifurcation analysis of fermentation of sugar to ethanol in presence of Saccharomyces cerivisiae at very high gravity is described. The bifurcation analysis was done for a concentration 280 gl−1 of sugar, and the dilution rate was taken as the parameter of bifurcation. Two Hopf bifurcations (HB) at 280 gl−1 were found. At dilution rate of 0.027 h−1 the system exhibits damped oscillations and not sustained oscillations as previously reported because the system is close to a point of attraction, and we can attenuate these oscillations by the choice of initial conditions. The system exhibits sustained oscillations between the two Hopf Bifurcations, the first at 0.08028 h−1 and the second at 0.04395 h−1. These oscillations are the consequence of synchrony between the daughter and the mother yeast. Indeed, it is better to take a dilution rate between the two Hopf bifurcations (self sustained oscillations), in order to increase the ethanol productivity.展开更多
Due to its merits of drought tolerance and high yield,sweet potatoes are widely considered as a potential alterative feedstock for bioethanol production.Very high gravity(VHG)technology is an effective strategy for im...Due to its merits of drought tolerance and high yield,sweet potatoes are widely considered as a potential alterative feedstock for bioethanol production.Very high gravity(VHG)technology is an effective strategy for improving the efficiency of ethanol fermentation from starch materials.However,this technology has rarely been applied to sweet potatoes because of the high viscosity of their liquid mash.To overcome this problem,cellulase was added to reduce the high viscosity,and the optimal dosage and treatment time were 8 U/g(sweet potato powder)and 1 h,respectively.After pretreatment by cellulase,the viscosity of the VHG sweet potato mash(containing 284.2 g/L of carbohydrates)was reduced by 81%.After liquefaction and simultaneous saccharification and fer-mentation(SSF),thefinal ethanol concentration reached 15.5%(v/v),and the total sugar conversion and ethanol yields were 96.5%and 87.8%,respectively.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.
文摘In this paper, a study of the bifurcation analysis of fermentation of sugar to ethanol in presence of Saccharomyces cerivisiae at very high gravity is described. The bifurcation analysis was done for a concentration 280 gl−1 of sugar, and the dilution rate was taken as the parameter of bifurcation. Two Hopf bifurcations (HB) at 280 gl−1 were found. At dilution rate of 0.027 h−1 the system exhibits damped oscillations and not sustained oscillations as previously reported because the system is close to a point of attraction, and we can attenuate these oscillations by the choice of initial conditions. The system exhibits sustained oscillations between the two Hopf Bifurcations, the first at 0.08028 h−1 and the second at 0.04395 h−1. These oscillations are the consequence of synchrony between the daughter and the mother yeast. Indeed, it is better to take a dilution rate between the two Hopf bifurcations (self sustained oscillations), in order to increase the ethanol productivity.
基金financial support from the National Natural Science Foundation of China(Grant No.20736006)the National Basic Research Program of China(Grant No.2007CB714301)+1 种基金the international collaboration project of MOST(2006DFA62400)Key Projects in the National Science&Technology Pillar Program(No.2007BAD42B02).
文摘Due to its merits of drought tolerance and high yield,sweet potatoes are widely considered as a potential alterative feedstock for bioethanol production.Very high gravity(VHG)technology is an effective strategy for improving the efficiency of ethanol fermentation from starch materials.However,this technology has rarely been applied to sweet potatoes because of the high viscosity of their liquid mash.To overcome this problem,cellulase was added to reduce the high viscosity,and the optimal dosage and treatment time were 8 U/g(sweet potato powder)and 1 h,respectively.After pretreatment by cellulase,the viscosity of the VHG sweet potato mash(containing 284.2 g/L of carbohydrates)was reduced by 81%.After liquefaction and simultaneous saccharification and fer-mentation(SSF),thefinal ethanol concentration reached 15.5%(v/v),and the total sugar conversion and ethanol yields were 96.5%and 87.8%,respectively.
基金Supported by the National Key Sci&Tech Project of the 11th 5-year Plan of China(No.2007BAD78B04)the Provincial Key Sci&Tech Project of Sichuan,China(No.027.X028-037)
