Optimization Of Fermentation Conditions For Clostridium Beijerinckii

Due to the pressure of environmental and energy crisis, development of biofuel has become an important strategy. Butanol, as an alternative biofuel with a series of advantages than ethanol, has attracted the views of many countries. Biobutanol production by effective microorganism fermentation appears feasible solution that could control cost.Clostridium beijerinckii NCIMB 8052 was taken as the original strain in this study, treated with low-energy ion beam implantation(named Clostridium beijerinckii CN18) and continuous culturing domestication. Finally we obtained a mutant with better inhibitor tolerance as well as butanol productivity, named Clostridium beijerinckii CN88. Afterwards, anaerobic fermentation was processed to evaluate its fermentative capability through OD600 value, ABE production and residual sugar by using TYA mediums with various lignin concentrations. The optimization of fermentation conditions, which including carbon source, nitrogen source and inoculum size, was addressed for utilizing the diluted bamboo enzymatic hydrolysate directly via supplementing nutrient ingredients.The butanol tolerance for this mutant C. beijerinckii CN18 was increased to 11.0 g/L, and which was 10.0 g/L for the NCIMB 8052. The results for 5 L batch fermentation showed that C. beijerinckii CN18 produced 15.01 g/L butanol and 19.55 g/L total acetone, butanol, ethanol(ABE) solvents, respectively, which were 45.16% and 49.01% higher than the NCIMB 8052. The fermentation period was shortened from 48 h for NCIMB 8052 to 44 h for the CN18. The productivity increased from 0.27 g/(L· h) to 0.44 g/(L· h). The genetic stability experiment showed that CN18 could be serial y passaged 20 times, meanwhile, the production of solvents maintained stable. In addition, through continuously selective culture domestication, the eventual tolerance point of CN88 reached 1.2 g/L of inhibitor and it could produce 3.6 g/L ABE solvents. It could produce 14.4 g/L of total solvent under the conditions of 0.6g/L lignin concentration. After the optimization of fermentation condition and practical fermentation test, 40% diluted bamboo enzymatic hydrolysate without detoxification step for CN88 were established to produce 12.9 g/L ABE solvents through supplementing glucose to 29.1 g/L, xylose to 12.9 g/L, yeast extract 2 g/L, 10% inoculation size under pH value 6.8 at 37 ℃ for anaerobic fermentation.A better inhibitor tolerance and solvent production were showed by C. beijerinckii CN88 compared to NCIMB 8052. And after optimization of fermentation condition, CN88 could eventual y use non-detoxified bamboo enzymatic hydrolysate to produce biofuel, which could avoid the lignin removal step.