The aim of this study was to prove that Terrilactibacillus laevilacticus SK5-6, a novel D-lactate producer, exhibited a good fermentation performance comparing to the reference D-lactate producer Sporolactobacillus sp. Glucose bioconversion for D-lactate production and the activity of five key enzymes including phosphofructokinase (PFK), pyruvate kinase (PYK), D-lactate dehydrogenase (D-LDH), L-lactate dehydrogenase (L-LDH), and lactate isomerase (LI) were investigated in the cultivation of T. laevilacticus SK5–6 and S. laevolacticus 0361T. T. laevilacticus SK5–6 produced D-lactate at higher yield, productivity, and optical purity compared with S. laevolacticus 0361T. T. laevilacticus SK5–6, the catalase-positive isolate, simultaneously grew and produced D-lactate without lag phase while delayed growth and D-lactate production were observed in the culture of S. laevolacticus 0361T. The higher production of D-lactate in T. laevilacticus SK5–6 was due to the higher growth rate and the higher specific activities of the key enzymes observed at the early stage of the fermentation. The low isomerization activity was responsible for the high optical purity of D-lactate in the cultivation of T. laevilacticus SK5–6. The lowest specific activity of PFK following by PYK and D/L-LDHs, respectively, indicated that the conversion of fructose-6-phosphate was the rate limiting step. Under the well-optimized conditions, the activation of D/L-LDHs by fructose-1,6-phosphate and ATP regeneration by PYK drove glucose bioconversion toward D-lactate. The optical purity of D-lactate was controlled by D/L-LDHs and the activation of isomerases. High D-LDH with limited isomerase activity was preferable during the fermentation as it assured the high optical purity.

中文翻译：

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D-乳酸发酵性能和新型细菌特异乳杆菌SK5-6的酶活性

这项研究的目的是证明与参考D-乳酸生产者Sporolactobacillus sp。相比，新型D-乳酸生产者latervilactbacillus laevilacticus SK5-6具有良好的发酵性能。葡萄糖的生物转化以产生D-乳酸以及包括磷酸果糖激酶（PFK），丙酮酸激酶（PYK），D-乳酸脱氢酶（D-LDH），L-乳酸脱氢酶（L-LDH）和乳酸异构酶（ LI）在T. laevilacticus SK5-6和S. laevolacticus 0361T的培养中进行了研究。与S. laevolacticus 0361T相比，T。laevilacticus SK5-6以更高的产量，生产率和光学纯度生产D-乳酸。T. laevilacticus SK5-6（过氧化氢酶阳性分离株）在S. laevolacticus 0361T的培养中观察到同时生长并产生D-乳酸而没有滞后相，同时观察到生长延迟和D-乳酸的产生。T. laevilacticus SK5-6中D-乳酸的产量较高，这是由于发酵初期观察到的关键酶的较高生长速率和较高比活性。低的异构化活性是D.乳酸菌在T. laevilacticus SK5-6培养中高光学纯度的原因。分别由PYK和D / L-LDH引起的PFK最低比活表明，果糖6-磷酸酯的转化是限速步骤。在充分优化的条件下，果糖1，，6-磷酸对D / L-LDHs的激活和PYK对ATP的再生推动了葡萄糖向D-乳酸的生物转化。D-乳酸的光学纯度由D / L-LDH和异构酶的激活控制。在发酵期间优选具有有限的异构酶活性的高D-LDH，因为其确保了高光学纯度。