REGULATION OF PRODUCT FORMATION DURING GLUCOSE OR LACTOSE LIMITATION IN NONGROWING CELLS OF STREPTOCOCCUS-LACTIS
REGULATION OF PRODUCT FORMATION DURING GLUCOSE OR LACTOSE LIMITATION IN NONGROWING CELLS OF STREPTOCOCCUS-LACTIS
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DOI：
10.1128/aem.48.2.332-337.1984
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发表时间：
1984-01-01
影响因子：
4.4
通讯作者：
THOMAS, TD
中科院分区：
文献类型：
--
作者：
FORDYCE, AM;CROW, VL;THOMAS, TD
不生长的S.在pH-stat中的乳酸菌中加入糖以允许以最大速率发酵，或者以低于最大速率的速率连续供给糖。在厌氧条件下，葡萄糖或乳糖的快速发酵基本上是纯乳酸的。对于菌株ML 3，限制发酵速率将大约一半的丙酮酸转移到甲酸盐、乙酸盐和乙醇。在限制葡萄糖发酵速率下，细胞含有较低浓度的乳酸脱氢酶激活剂（果糖1，6-二磷酸）和丙酮酸甲酸裂解酶抑制剂（磷酸丙糖）。因此，丙酮酸甲酸裂解酶和丙酮酸脱氢酶在丙酮酸代谢中发挥更大的作用。与菌株ML 3相反，菌株ML 8在厌氧条件下不产生相同的产物转移，并且细胞保留更高浓度的上述效应化合物。在有氧条件下，乳糖代谢导致丙酮酸分泌的两个S。乳酸菌ML 3和ML 8。在7%的最大利用率下，丙酮酸分别占ML 3和ML 8代谢乳糖的69%和35%。醋酸盐也是一种主要产品，尤其是ML 8。显然，在O2存在下，NADH氧化酶参与coenzme再循环，丙酮酸甲酸裂解酶失活，但丙酮酸脱氢酶复合物仍起作用。
Nongrowing cells of S. lactis in a pH-stat were dosed with sugar to allow fermentation at the maximum rate or were fed a continuous supply of sugar at rates less than the maximum. Under anaerobic conditions, rapid fermentation of either glucose or lactose was essentially homolactic. With strain ML3, limiting the fermentation rate diverted approximately half of the pyruvate to formate, acetate and ethanol. At limiting glucose fermentation rates, cells contained lower concentrations of lactate dehydrogenase activator (fructose 1,6-diphosphate) and pyruvate formate-lyase inhibitors (triose phosphates). As a result, pyruvate formate-lyase and pyruvate dehydrogenase play a greater role in pyruvate metabolism. In contrast to strain ML3, strain ML8 did not give the same diversion of products under anaerobic conditions, and cells retained higher concentrations of the above effector compounds. Lactose metabolism under aerobic conditions resulted in pyruvate excretion by both S. lactis ML3 and ML8. At 7% of the maximum utilization rate, pyruvate accounted for 69 and 35% of the lactose metabolized by ML3 and ML8, respectively. Acetate was also a major product, especially with ML8. Evidently, NADH oxidase is involved in coenyzme recycling in the presence of O2 and pyruvate formate-lyase is inactivated, but the pyruvate dehydrogenase complex still functions.