L-lactic acid fermentation at low pH reduces the use of neutralizers during fermentation and the generation of solid wastes in purification processes. Most lactic acid bacteria exhibit weak tolerance and poor cell viability at low pH. This study proposes a pH shifting adaptive evolution method to improve the low-pH tolerance of an engineered Pediococcus acidilactici strain. In the first stage, cells were cultured at a moderate pH to maintain the cell viability, then shifted to a low pH to enhance low-pH tolerance. Long-term pH shifting evolution culture of the engineered P. acidilactici between the moderate and low pH resulted in a 43 % increase in L-lactic acid production at pH 4.6 (110.4 g/L) and a 2.1-fold increase at pH 4.4 (80.7 g/L) compared to the parental strain when using wheat straw as a feedstock. This pH-shifting adaptive evolution strategy provides an effective tool for improving the low-pH tolerance of lactic acid bacteria.

中文翻译：

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pH 值变化适应性进化刺激乳酸片球菌的低 pH 耐受性和高 L-乳酸发酵效率


在低 pH 值下进行 L-乳酸发酵可减少发酵过程中中和剂的使用以及净化过程中固体废物的产生。大多数乳酸菌在低 pH 值下表现出较弱的耐受性和较差的细胞活力。本研究提出了一种 pH 值变化适应性进化方法，以提高工程酸性片球菌菌株的低 pH 耐受性。在第一阶段，将细胞在中等 pH 值下培养以维持细胞活力，然后转移到低 pH 值以增强低 pH 值耐受性。在中等和低 pH 值之间，工程化的酸乳假单胞菌的长期 pH 值变化进化培养导致，当使用小麦秸秆作为原料时，与 pH 4.6 （110.4 g/L） 相比，L-乳酸产量增加了 43%，在 pH 值 4.4 （80.7 g/L） 时增加了 2.1 倍。这种 pH 值变化的适应性进化策略为提高乳酸菌的低 pH 耐受性提供了有效的工具。