Batonal Production By Clostridium Acetobutylicum And Primary Studies On Metabolic Regulation

Butanol as the end product is toxic to the cell,which restrict the the total final concentration of solvent.As a result,the following costs are relatively high and it is difficult to compete with chemical synthesis.Strain improvements,therefore,focus on the isolation of strains with high butanol production and tolerance so as to reduce the production costs.In this paper,a strain named Clostridium acetobutylicum UV-1 treated with UV was selected and the butanol yeids were 9.88g/L,10.02% higher than the original strain.Then C.acetobutylicum UV-1 was treated with nitrous acid,which resulted of a strain named C.acetobutylicum NA-34.At last, C.acetobutylicum NA-34 was treated by a serial enrichment procedure with butanol.The butanol yeids reached 12.81g/L .The mutant was genetically stable.Compared with C.acetobutylicum E3-1,theα-amylase activity of C.acetobutylicum BR8-1elevated by 58.20%.As the metabolites glucose,maltose and dextrin all can inhibit theα-amylase activity of C.acetobutylicum E3-1 more than C.acetobutylicum BR8-1.Among them,glucose had the strongest inhibitory effect.With the increase of the glucose concentration,the effect of inhibitory elevated.When the glucose concentration reached 4.00%,more than 88.00%α-amylase activity were repressed.At the same time,it was found that glucose impacted theα-amylase activity mainly in the logarithmic phase.These studies indicated that C.acetobutylicum BR8-1 was a strain Resistant to catabolite repression.But it can not resist catabolite repression completely.With solvent production as the main index, the cassava starch pretreatment coditions as well as fermentation conditions were studied.The cassava starch pretreatment coditions:60 mesh,temperature 90℃for 60min;fermentation conditions:initial pH5.2;temperature37℃; inoculation size 7.00%; inoculation time 26h. with solvent production and residual sugar amount as indexs,7.00% cassava starch was selected as carbon source,1.00% wheat bran plus 0.25% yeast extract were slected as nitrogen source,and 25.00%waste liquid.Neutral red made the flow towards butanol and ethanol.When 0.10% neutral red was added to the culture, the ratio of butanol increased from 60.35% to 66.43%,and the ratio of ethnol increased from 10.19% to 15.84%;meanwhile,the ratio of acetone decreased from 29.46% to 17.73%.Sodium acetate played a role in making the flow towards butanol and acetone.When 0.60% sodium acetate was added to the culture,the ratio of butanol increased from 60.97% to 64.78%,and the ratio of acetone increased from29.00% to 33.44%.