The Growth And Fermentation Characteristics And Ethanol-tolerant Adaption Of Thermoanaerobacterium Saccharolyticum

This paper studied on the ethanol-tolerant adaption, growth and fermentation characteristics of T. saccharolyticum.This stain showed best growth characteristic while the carbon source of the medium was mannose, glucose or xylose. Optimum concentration of substrate is 15 g/L. Different ratio of glucose:xylose didn't show notable influence on the growth of'T. saccharolyticum. The highest tolerance of ethanol is 3%(v/v). The changes of product concentration and OD of the medium during the fermentation were studied. When the carbon source of the medium varied from 5 g/L xylan, xylose to cassava starch, the ethanol concentration after 60 h fermentation is 0.824,0.867,0.9162 g/L, respectively. When the T. saccharolyticum was cultured in medium containing 50 g/L xylose or cassava starch in a bioreactor with pH controlled at 6.0, the highest concentration of ethanol was 7.502 g/L and 5.83 g/L, which were obtained at 48 h and 72 h respectively.When T. saccharolyticum was cultured in 10 g/L cassava starch or xylan for 24 h, the activity of amylase and xylanase in the medium was 0.25 U/mL and 0.35 U/mL respectively. When T. saccharolyticum was cultured in 50 g/L cassava starch and xylan in the bioreactor, the highest activity of amylase and xylanase was 0.74 and 0.70 U/mL respectively, which were both achieved at 24 h., Ethanol-tolerance of T. saccharolyticum was adapted by enhancing the concentration of ethanol in the medium gradually. A mutant showed the ability to grow in the medium containing 5%(v/v) ethanol. Compared to the wildtype, the ethanol-tolerant ability of this mutant was improved by 67%. However, the mutant didn't show significant improvement in substrate-tolerance.When the wildtype and the mutant was cultured in 10 g/L xylose respectively, determined the concentration of substrates and products after 72 h. The wildtype utilized 7.24 g/L xylose while the mutant untilized 5.35 g/L xylose. The production of lacid acid by the willdtype and mutant was 2.91 g/L and 2.64 g/L with a yield of 0.40 and 0.49 g/g. The acetic acid production by the willdtype and the mutant was 0.73 g/L and 0.58 g/L with a yield of0.10�'�and 0.11 g/g, and the ethanol production by the willdtype and the mutant was 1.35 g/L and 1.36 g./L with a yield of 0.19 and 0.25 g/g.