Glucose and xylose co-fermentation of pretreated wheat straw using mutants of S. cerevisiae TMB3400
Wheat straw was pretreated and fermented to ethanol. Two strains, which had been mutated from the genetically modified Saccharomyces cerevisiae TMB3400, KE6-12 and KE6-13i, have been used in this study and the results of performance were compared to that of the original strain. The glucose and xylose co-fermentation ability was investigated in batch fermentation of steam-pretreated wheat straw (SPWS) liquid (undiluted, and diluted 1.5 and 2 times). Both strains showed improved xylose uptake in diluted SPWS liquid, and increased ethanol yields compared with the original TMB3400 strain, although xylitol formation also increased slightly. In undiluted SPWS liquid, however, only KE6-13i performed better than the original strain regarding xylose utilization.Fed-batch fermentation of 1.5 and 2 times diluted liquid was performed by adding the glucose-rich hydrolysates from enzymatic hydrolysis of the solid fraction of SPWS at a constant feed rate after 5 h of fermentation, when the glucose had been depleted. The modified strains showed improved xylose conversion; however, the ethanol yield was not significantly improved due to increased glycerol production. Fed-batch fermentation resulted in faster xylose utilization than in the batch cases.
► Performance of the mutants of S. cerevisiae TMB3400 was investigated. ► Improved xylose conversion has been shown by the mutated strains. ► Increased ethanol yield is reported for the mutated strains. ► Fed-batch fermentation has been shown to be beneficial for all strains.
Journal: Journal of Biotechnology - Volume 164, Issue 1, 10 March 2013, Pages 50–58