Phenolic acids are lignin-derived fermentation inhibitors formed during many pretreatment processes of lignocellulosic biomass. In this study, vanillic, p-hydroxybenzoic, and syringic acids were selected as the model compounds of phenolic acids, and the effect of short-term adaptation strategies on the tolerance of S. cerevisiae to phenolic acids was investigated. The mechanism of phenolic acids tolerance in the adapted yeast strains was studied at the morphological and physiological levels. The multiple phenolic acids exerted the synergistic inhibitory effect on the yeast cell growth. In particular, a significant interaction between vanillic and hydroxybenzoic acids was found. The optimal short-term adaptation strategies could efficiently improve the growth and fermentation performance of the yeast strain not only in the synthetic media with phenolic acids, but also in the simultaneous saccharification and ethanol fermentation of corncob residue. Morphological analysis showed that phenolic acids caused the parental strain to generate many cytoplasmic membrane invaginations with crack at the top of these sites and some mitochondria gathered around. The adapted strain presented the thicker cell wall and membrane and smaller cell size than those of the parental strain. In particular, the cytoplasmic membrane generated many little protrusions with regular shape. The cytoplasmic membrane integrity was analyzed by testing the relative electrical conductivity, leakage of intracellular substance, and permeation of fluorescent probe. The results indicated that the short-term adaptation improved the membrane integrity of yeast cell. The inhibition mechanism of phenolic acid might be attributed to the combined effect of the cytoplasmic membrane damage and the intracellular acidification. The short-term adaptation strategy with varied stressors levels and adaptive processes accelerated the stress response of yeast cell structure to tolerate phenolic acids. This strategy will contribute to the development of robust microbials for biofuel production from lignocellulosic biomass.

中文翻译：

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短期适应提高酿酒酵母对木质素衍生酚酸在木质纤维素乙醇发酵中的耐受性的生理机制

酚酸是在木质纤维素生物质的许多预处理过程中形成的源自木质素的发酵抑制剂。本研究选择香草酸、对羟基苯甲酸和丁香酸作为酚酸的模型化合物，研究短期适应策略对酿酒酵母对酚酸耐受性的影响。在形态和生理水平上研究了适应酵母菌株中酚酸耐受的机制。多种酚酸对酵母细胞生长发挥协同抑制作用。特别是，发现香草酸和羟基苯甲酸之间存在显着的相互作用。优化的短期适应策略不仅可以有效提高酵母菌株在酚酸合成培养基中的生长和发酵性能，而且可以在玉米芯残渣的同时糖化和乙醇发酵中有效地提高酵母菌株的生长和发酵性能。形态学分析表明，酚酸导致亲本菌株产生许多细胞质膜内陷，这些位点顶部有裂缝，一些线粒体聚集在周围。与亲本菌株相比，适应菌株具有更厚的细胞壁和细胞膜以及更小的细胞大小。特别是细胞质膜上产生了许多形状规则的小突起。通过测试相对电导率、细胞内物质渗漏、和荧光探针的渗透。结果表明，短期适应提高了酵母细胞的膜完整性。酚酸的抑制机制可能归因于细胞质膜损伤和细胞内酸化的共同作用。具有不同压力源水平和适应过程的短期适应策略加速了酵母细胞结构对酚酸耐受的应激反应。该策略将有助于开发用于从木质纤维素生物质生产生物燃料的强大微生物。具有不同压力源水平和适应过程的短期适应策略加速了酵母细胞结构对酚酸耐受的应激反应。该策略将有助于开发用于从木质纤维素生物质生产生物燃料的强大微生物。具有不同压力源水平和适应过程的短期适应策略加速了酵母细胞结构对酚酸耐受的应激反应。该策略将有助于开发用于从木质纤维素生物质生产生物燃料的强大微生物。