乳酸菌的乙醇耐受机制及其在食醋生产中的应用

传统固态发酵食醋因其丰富的菌群在风味、品质等方面有着不可比拟的优势，乳酸菌作为固态食醋发酵中重要的功能微生物，广泛应用于食品、生物等领域。然而，食醋在发酵过程中乳酸菌会受到高乙醇环境的胁迫，因此探究乳酸菌如何在高乙醇环境下生存具有积极意义。该研究选择耐乙醇副干酪乳杆菌（PC-5）和不耐乙醇植物乳杆菌（PR-7）作为实验对比菌株，通过检测生物指标发现：在体积分数为8%的乙醇环境下，PC-5的多糖含量占比和细胞膜通透性分别提高至0.56%和75%，且显著高于PR-7。此外，代谢途径中的己糖激酶（Hexokinase,HK）、6-磷酸果糖激酶（6-Phosphofructokinase,PFK）、丙酮酸激酶（PyruvateKinase,PK）的活性均高于PR-7，并分别提高至99.82、2.78、3.43 U/mg。最后，在食醋不同发酵阶段中加入PC-5使其与酵母菌实现共同发酵，结果发现：共发酵食醋体系中多酚的生成和总抗氧化能力比单菌发酵分别提升了32.14%和55.56%。因此乳酸菌对食醋发酵有着良好的促进作用，为乳酸菌参与食醋共发酵提供了良好的理论依据。

Ethanol Tolerance Mechanism of Lactic Acid Bacteria and Its Application in Vinegar Fermentation

Traditional solid-state fermented vinegar has superior flavor and quality due to its rich flora. As lactic acid bacteria are important functional microorganisms in solid-state vinegar fermentation, they are widely used in food-related and biological fields. However, lactic acid bacteria are stressed by high ethanol concentrations during vinegar fermentation. Therefore, how lactic acid bacteria survive at high ethanol concentrations should be explored. In this study, ethanol-tolerant Lactobacillus paracasei PC-5 and ethanol-intolerant Lactobacillus plantarum PR-7 were selected for comparison. Based on the biological indicators, the polysaccharide content and cell membrane permeability of PC-5 increased to 0.56% and 75%, respectively, and were significantly higher than those of PR-7 in an ethanol environment with a volume fraction of 8%. PC-5 outperformed PR-7 in terms of the activities of hexokinase (HK), 6-phosphofructokinase (PFK), and pyruvate kinase (PK) in the metabolic pathway, with activities increasing to 99.80, 2.78, and 3.43 U/mg, respectively. Finally, PC-5 was added to the vinegar at different fermentation stages to achieve mixed culture co-fermentation with yeast. Polyphenol production and total antioxidant capacity were found to increase by 32.14% and 55.56%, respectively, compared with those of single culture bacteria fermentation. Therefore, lactic acid bacteria had positive stimulation effects on vinegar fermentation. Such findings provide a good theoretical basis for the use of lactic acid bacteria in mixed culture fermentation of vinegar.