Lund University, Department of Chemical Engineering, PO Box 124, SE-221 00 Lund, Sweden.
J Biotechnol. 2013 Mar 10;164(1):50-8. doi: 10.1016/j.jbiotec.2012.12.003. Epub 2012 Dec 20.
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.
小麦秸秆经预处理后用于发酵生产乙醇。本研究采用了两株经过基因修饰的酿酒酵母突变株（KE6-12 和 KE6-13i），与原始菌株 TMB3400 的性能进行了比较。在蒸汽预处理小麦秸秆（SPWS）液体的分批发酵中（未稀释、稀释 1.5 倍和 2 倍），考察了两株菌的葡萄糖和木糖共发酵能力。与原始 TMB3400 菌株相比，两株菌在稀释的 SPWS 液体中对木糖的摄取能力均有所提高，乙醇得率也有所提高，尽管木糖醇的形成略有增加。然而，在未稀释的 SPWS 液体中，只有 KE6-13i 对木糖的利用优于原始菌株。当发酵 5 小时后葡萄糖耗尽时，采用恒速进料的方式，向酶解 SPWS 固体部分得到的富含葡萄糖的水解液中添加 1.5 倍和 2 倍稀释液，进行补料分批发酵。修饰后的菌株提高了木糖转化率；然而，由于甘油产量增加，乙醇得率并没有显著提高。与分批发酵相比，补料分批发酵能更快地利用木糖。
