Studies On Butanol Production By Clostridium Acetobutylicum From Jerusalem Artichokes

Biobutanol is a new potential biofuel and has attracted worldwide attention.Although starch raw materials are traditionally used to produce butanol,due to the high cost of raw materials,it is not competitive with petroleum fuel in the price.Jerusalem artichoke(JA) is one of alternative raw materials to produce biobutanol and other bio-based chemicals.In this study Clostridium acetobutylicum L7 was employed to ferment the hydrolysate of JA,fructose and glucose in order to provide low-cost raw materials for the production of biobutanol.The main results are as follows:Culture medium and fermentation conditions for butanol production by C.acetobutylicum L7 were optimized with single factor and uniform design experiment.The optimum medium and the optimum fermentation conditions were as follows:glucose 50 g/L,ammonium acetate 2.3 g/L,KH₂PO₄ 0.5 g/L,K₂HPO₄ 0.5 g/L,MgSO₄·7H₂O 0.2 g/L,anthranilic acid 0.01 g/L,the initial pH 5.5,the optimum fermentation temperature 37.5℃.Under the optimized conditions for enlarge culture in 1 L fermentor,the concentration of butanol increased from original 5.84 g/L up to 8.09 g/L,which was 38.53%higher than before optimization;the concentration of total solvents up to 15.07 g/L,which was 33.72%higher than the original conditions and the ratio of butanol in total solvents increased 4.23%.The feasibility of producing butanol through the fermentation of Jerusalem artichoke was studied.The effluence of different substrates-glucose,fructose,JA and different concentration of JA(50 g/L,60 g/L,80 g/L) has been compared.The results showed that C. acetobutylicum L7 could ferment the hydrolysis of JA well.Glucose could be consumed more rapidly by C.acetobutylicum L7,comparing with other two substrates.There was no significant difference when fructose and JA juice were used as substrate.And the transformation from organic acids to solvents was slowly.Fermenting with different concentration of JA-50 g/L,60 g/L,80 g/L,the production of butanol was improved with the increasing concentration of JA juice,which was 8.67 g/L,11.99 g/L,12.56 g/L, respectively.When the concentration of JA juice reached 80 g/L,serious inhibition from substrates and products was observed.Both the percentage of sugar consumption and butanol yield were decreased,which were 59.2%and 0.13 g/g,respectively.In order to learn the growth characteristics of C.acetobutylicum L7,kinectics analysis for C.acetobutylicum L7 in batch fermentation had been conducted.Cell growth,substrate consumption and production of butanol,acetone,butyric acid and acetic acid were studied in -batch system.The results showed that there was different synthetical metabolize in different pH.The higher the fermentation pH,the more favor to the synthesis of organic acids,on the contrary,the more conducive to the synthesis of solvents.The optimum growth pH was between 5.0～5.5;butyric acid and acetic acid were produced mainly between pH5.5～6.0; solvents were synthesized below pH5.0.Butanol,butyric acid and acetic acid were important inhibitors.