Greetham D, Takagi H, Phister T P
School of Biosciences, University of Nottingham, Loughborough, Leicestershire, LE12 5RD, UK,
Antonie Van Leeuwenhoek. 2014 Apr;105(4):641-52. doi: 10.1007/s10482-014-0118-3. Epub 2014 Feb 6.
Fermentation of sugars released from lignocellulosic biomass (LCMs) is a sustainable option for the production of bioethanol. LCMs release fermentable hexose sugars and the currently non-fermentable pentose sugars; ethanol yield from lignocellulosic residues is dependent on the efficient conversion of available sugars to ethanol, a side-product of the process is acetic acid production. Presence of acetic acid reduced metabolic output and growth when compared with controls; however, it was observed that incubation with proline had a protective effect, which was proline specific and concentration dependent; the protective effect did not extend to furan or phenolic stressed yeast cells. Proline accumulating strains displayed tolerance to acetic acid when compared with background strains, whereas, strains with a compromised proline metabolism displayed sensitivity. Sensitivity to weak acids appears to be reduced with the addition of proline; proline is an imino acid freely available as a nitrogen source in the aerobic phase of fermentations. Yeast strains with higher intracellular proline concentrations would be desirable for industrial bioethanol fermentations.
从木质纤维素生物质（LCMs）中释放的糖发酵是生产生物乙醇的可持续选择。LCMs会释放可发酵的己糖和目前不可发酵的戊糖；木质纤维素残渣的乙醇产量取决于可用糖向乙醇的有效转化，该过程的一个副产品是乙酸的产生。与对照相比，乙酸的存在会降低代谢产量和生长；然而，观察到用脯氨酸孵育具有保护作用，这种保护作用具有脯氨酸特异性且依赖于浓度；这种保护作用并不扩展到呋喃或酚类胁迫的酵母细胞。与背景菌株相比，脯氨酸积累菌株对乙酸具有耐受性，而脯氨酸代谢受损的菌株则表现出敏感性。添加脯氨酸似乎会降低对弱酸的敏感性；脯氨酸是一种亚氨基酸，在发酵的需氧阶段可作为氮源自由获取。对于工业生物乙醇发酵而言，具有较高细胞内脯氨酸浓度的酵母菌株将是理想的。
