Effect Of Ca²⁺ On Acetone-Butanol Fermentation From Corn Stalk Hydrolysate

Butanol production from corn stover hydrolysates(CSH)has obvious advantages in the field of biomass conversion.On the one hand,energy production relaxed the crisis that petroleum energy shortage formed,on the other hand,it solved environmental problems that burned down or thrown out agricultural waste materials formed.In order to explore the effect mechanism of exogenous Ca2+ on butanol fermentation from corn stalk hydrolysate and an efficient technology system for butanol fermentation of corn stalk hydrolysate was obtained.The content of this research is as follows:(1)The influence of Ca2+ on the butanol fermentation from corn stalk hydrolysate was explored.The intracellular Ca2+ content was significantly reduced by the hydrolysate butanol fermentation,and the Ca2+ level in the cell could be restored by adding exogenous Ca2+.The addition of exogenous Ca2+ can also significantly improve the utilization rate of sugar,but the increased sugar consumption is mainly used to produce acetic acid and butyric acid while only a small fraction is used to generate solvents.Enzyme activity analysis found that adding exogenous Ca2+ can promote acetate kinase and butyric acid kinase activity,but Ca CO3 inhibits the coenzyme A transferase activity,which is no difference in the activity of the enzyme related to the solvent;adding Ca CO3 can significantly improve the overall level of coenzyme,and decrease the ratio of NAD+/NADH,as well as increase the overall level of intracellular ATP,but reduce the ratio of ATP/ADP.(2)Adding intracellular Ca2+ inhibitor(BAPTA-AM)to inhibit intracellular Ca2+ levels,the effect of intracellular Ca2+ concentration on the butanol fermentation process was investigated.The results indicated that the addition of bapta-am in trace amount had a significant effect on the intracellular Ca2+ level,and the inhibitory effect could be alleviated by adding Ca CO3.The inhibitory effect of BAPTA-AM was to restrict intracellular Ca2+ levels and inhibit metabolic activity,including glucose consumption,coenzyme A transferase activity,NADH and NADPH levels.(3)Single factor experimental results indicated that the total sugar content of 70 g/L,the amount of added Ca CO3 to 5 g/L have the most obvious promoting effect on the yield of solvent.Electron transportor neutral red,riboflavin and reducing substances Na2 S,Fe SO4 promote the production of solvent in varying degrees.The orthogonal experimental results show that the effect of neutral red-Na2 S on solvent yield is not significant.Riboflavin-Fe SO4 has obvious promoting effect to solvent production(P < 0.05),the addition of riboflavin and Fe SO4 were 0.1g /L and 0.15 g /L have the highest yield of butanol and total solvent(9.685 g/L and 13.64 g/L),which were increased by 31.59% and 45.88% compared with the control(addition of calcium carbonate alone),respectively;neutral red-Fe SO4 also have obvious promoting effect to solvent production(P < 0.05),the addition of neutral red and Fe SO4 were 0.1 g/L and 0.1 g/L have the highest yield of butanol and total solvent(11.5 g/L and 14.72 g/L),which were increased by 56.25% and 57.43% compared with the control,respectively.Adding electron transportor can significantly increase the proportion of butanol in solvent,the butanol rate were 79.34% and 78.23% with separate add neutral red and add riboflavin Fe SO4 combination,respectively,which increased by 9.9% and 8.9% than that of control.