Optimization of the Synthetic Medium Using RSM for Ethanol Production by Thermoanaerobacter sp. X514

Ling Xiaofang1 Xie Tian2 Yang Jing1(1The Key Laboratory of Biofuels,Qingdao Institute of Bioenergy and Bioprocess Technology,Chinese Academy of Sciences,Qingdao 266101; 2Applied and Environmental Microbiology Center,Chengdu Institute of Biology,Chinese Academy of Sciences,Chengdu 610041)

CBP Thermoanaerobacter Ethanol fermentation B family vitamins RSM

Thermoanaerobacter sp.X514 can ferment both xylose and pentose to ethanol,which is a promising strain to be applied into the cellulosic ethanol production.In the primary screening experiment,B family vitamins in yeast extract are found to be the main components contributing to the ethanol production.The further experiment reveals the most important six kinds of vitamins among B family vitamins.Together with three other factors,pH,NH4Cl,MgCl2 which contribute to the fermentation,totally nine variables are introduced in the medium optimization process.Further study with Plackett-Burman design reveals that among all factors in the synthetic medium,NH4Cl,nicotinic acid and thiamine are critical to the ethanol production.By means of the steepest ascent experiment and the followed Response Surface Methodology(RSM),it is found out that the fermentation can theoretically reach its maximum,when the concentrations of NH4Cl,nicotinic acid and thiamine reach 1.05 g/L,6.4 mg/L and 7.0 mg/L,respectively.Under the optimal condition,with 5 g/L glucose as the substrate,the predicted ethanol production is 34.46 mmol/L,in good agreement with the experimental production in the batch fermentation 33.78 mmol/L,which is about 5.1 times the original ethanol production of X514 in mineral medium.