Food Fermentation Laboratory, Agricultural Research Service, U.S. Department of Agriculture, and North Carolina Agricultural Research Service, Department of Food Science, North Carolina State University, Raleigh, North Carolina 27695-7624.
Appl Environ Microbiol. 1990 Jul;56(7):2120-4. doi: 10.1128/aem.56.7.2120-2124.1990.
In this study, we determined the internal cellular pH response of Leuconostoc mesenteroides and Lactobacillus plantarum to the external pH created by the microorganisms themselves or by lactic or acetic acids and their salts added to the growth medium. Growth of Leuconostoc mesenteroides stopped when its internal pH reached 5.4 to 5.7, and growth of L. plantarum stopped when its internal pH reached 4.6 to 4.8. Variation in growth medium composition or pH did not alter the growth-limiting internal pH reached by these microorganisms. L. plantarum maintained its pH gradient in the presence of either 160 mM sodium acetate or sodium lactate down to an external pH of 3.0 with either acid. In contrast, the DeltapH of Leuconostoc mesenteroides was zero at pH 4.0 with acetate and 5.0 with lactate. No differences were found between d-(-)- and l-(+)-lactic acid for the limiting internal pH for growth of either microorganism. The comparatively low growth-limiting internal pH and ability to maintain a pH gradient at high organic acid concentration may contribute to the ability of L. plantarum to terminate vegetable fermentations.
在这项研究中，我们确定了肠膜明串珠菌和植物乳杆菌对由微生物自身产生的外部 pH 以及添加到生长培养基中的乳酸或乙酸及其盐所产生的内部细胞 pH 响应。当肠膜明串珠菌的内部 pH 值达到 5.4 至 5.7 时，其生长停止，而当植物乳杆菌的内部 pH 值达到 4.6 至 4.8 时，其生长停止。生长培养基组成或 pH 值的变化不会改变这些微生物达到的生长限制内部 pH 值。在外部 pH 值为 3.0 时，无论是哪种酸，植物乳杆菌都能在 160mM 醋酸钠或乳酸钠存在的情况下维持其 pH 梯度。相比之下，在 pH 值为 4.0 时，肠膜明串珠菌的ΔpH 值为零，在 pH 值为 5.0 时，ΔpH 值为零。对于这两种微生物的生长限制内部 pH 值，d-(-)-和 l-(+)-乳酸之间没有发现差异。较低的生长限制内部 pH 值和在高有机酸浓度下维持 pH 梯度的能力可能有助于植物乳杆菌终止蔬菜发酵。
