He Xianlin, Liu Bo, Xu Yali, Chen Ze, Li Hao
Beijing Key Laboratory of Bioprocess, College of Life Science and Technology, Beijing University of Chemical Technology, Beijing, 100029, China.
Shandong Provincial Key Laboratory of Biopharmaceuticals, Shandong Academy of Pharmaceutical Sciences, Jinan, 250101, China.
Appl Microbiol Biotechnol. 2021 Mar;105(6):2597-2611. doi: 10.1007/s00253-021-11198-x. Epub 2021 Mar 1.
The bioethanol fermentation by Saccharomyces cerevisiae is often challenged by bacterial contamination, especially lactic acid bacteria (LAB). LAB can inhibit the growth S. cerevisiae by secreting organic acids and competing for nutrients and physical space. However, the range of favorable effects attributed to LAB during bioethanol fermentation, and their associated mechanisms of regulation, are not fully understood. This study was performed to clarify the effects of Lactobacillus plantarum, an important contaminative LAB in bioethanol fermentation, on the mechanism of ethanol tolerance in S. cerevisiae. The results showed that the presence of L. plantarum increased the ethanol tolerance of S. cerevisiae by promoting or inhibiting various metabolic processes in the yeast cells: The metabolism of trehalose, ergosterol, certain amino acids, proton pumps, stress response transcriptional activators, and heat shock proteins were all promoted; amounts of intracellular monounsaturated fatty acids and the accumulation of reactive oxygen species were inhibited. Furthermore, the maintenance of the acquired higher ethanol tolerance of S. cerevisiae was dependent on the coexistence of L. plantarum. These results suggested a complex relationship existed between S. cerevisiae and the contaminating LAB that might also play a beneficial role during fermentation by promoting the ethanol tolerance of yeast. The results from this study suggested that the extent of controlling bacterial contamination on bioethanol fermentation efficiency should be given careful consideration. KEY POINTS: • L. plantarum improved the ethanol tolerance of S. cerevisiae. • L. plantarum regulated the ethanol tolerance-related metabolism of yeast cells. • L. plantarum coexistence facilitated maintenance of ethanol tolerance in yeast cells.
酿酒酵母进行生物乙醇发酵时常常受到细菌污染的挑战，尤其是乳酸菌（LAB）。乳酸菌可通过分泌有机酸以及竞争营养物质和物理空间来抑制酿酒酵母的生长。然而，乳酸菌在生物乙醇发酵过程中所产生的有利影响范围及其相关调控机制尚未完全明确。本研究旨在阐明植物乳杆菌（生物乙醇发酵中一种重要的污染性乳酸菌）对酿酒酵母乙醇耐受性机制的影响。结果表明，植物乳杆菌的存在通过促进或抑制酵母细胞中的各种代谢过程提高了酿酒酵母的乙醇耐受性：海藻糖、麦角固醇、某些氨基酸的代谢、质子泵、应激反应转录激活因子和热休克蛋白均得到促进；细胞内单不饱和脂肪酸的含量以及活性氧的积累受到抑制。此外，酿酒酵母所获得的较高乙醇耐受性的维持依赖于植物乳杆菌的共存。这些结果表明酿酒酵母与污染性乳酸菌之间存在复杂的关系，这种关系在发酵过程中可能通过提高酵母的乙醇耐受性发挥有益作用。本研究结果表明，在控制细菌污染对生物乙醇发酵效率的影响程度方面应予以慎重考虑。要点：• 植物乳杆菌提高了酿酒酵母的乙醇耐受性。• 植物乳杆菌调节了酵母细胞与乙醇耐受性相关的代谢。• 植物乳杆菌的共存促进了酵母细胞乙醇耐受性的维持。
