Stimulation of D- and L-lactate dehydrogenases transcriptional levels in presence of diammonium hydrogen phosphate resulting to enhanced lactic acid production by Lactobacillus strain
Stimulation of D- and L-lactate dehydrogenases transcriptional levels in presence of diammonium hydrogen phosphate resulting to enhanced lactic acid production by Lactobacillus strain
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DOI：
10.1016/j.jbiosc.2017.07.009
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发表时间：
2017-12-01
影响因子：
2.8
通讯作者：
Sonomoto, Kenji
中科院分区：
文献类型：
--
作者：
Singhvi, Mamata;Zendo, Takeshi;Sonomoto, Kenji
研究了氮源对乳酸杆菌NCIM2368及其突变株RM2-24经紫外线诱变后产生的D-乳酸脱氢酶和L-乳酸脱氢酶活力的影响。对亲本菌株和突变菌株在对照和改良培养基中的ID-乳酸产量进行了评价。改良后的培养基对双亲的乳酸产量没有显着影响，而突变株的D-乳酸产量显着提高，发酵液中出现L-乳酸。突变株的乳酸脱氢酶活力和比活力均高于亲本菌株。这些结果表明，改良培养基中的磷酸氢二铵触发了乳酸脱氢酶基因的表达，从而提高了乳酸产量。用定量RT-PCR法研究了亲本和突变体的D-和L-乳酸脱氢酶基因在对照和改良培养基中的表达水平，证实了这一点。在突变株中，D-乳酸脱氢酶和L-乳酸脱氢酶在改良培养基中的转录水平分别比对照培养基高17倍和1.38倍。亲本细胞在对照和改良培养基中培养时，D-乳酸脱氢酶和L-乳酸脱氢酶的转录水平均无明显变化。本研究表明，突变体RM2-24含有L-乳酸脱氢酶基因，该基因在磷酸二氢铵存在下表达，导致L-乳酸的产生。D-乳酸发酵过程中的L-乳酸联产可能不利于聚乳酸的生产。(C)2017年，日本生物技术学会。版权所有。
The present study revealed the effect of nitrogen sources on lactic acid production and stimulation of D- and L-lactate dehydrogenases (LDH) of parent Lactobacillus lactis NCIM 2368 and its mutant RM2-24 generated after UV mutagenesis. Both the parent and mutant strains were evaluated for ID-lactic acid production in control and modified media. The modified media did not show remarkable effect on lactic acid production in case of parent whereas mutant exhibited significant enhancement in D-lactic acid production along with the appearance of L-lactic acid in the broth. Both LDH activities and specific activities were found to be higher in mutant than the parent strain. These results suggested that the diammonium hydrogen phosphate in modified media triggered the expression of LDH genes leading to enhanced lactic acid production. This observation has been proved by studying the expression levels of D- and L-LDH genes of parent and mutant in control and modified media using quantitative RT-PCR technique. In case of mutant, the transcriptional levels of D-LDH and L-LDH increased similar to 17 fold and similar to 1.38 fold respectively in modified medium compared to the values obtained with control medium. In case of parent, no significant change in transcriptional levels of D- and L-LDH was found when the cells were grown in either control medium or modified medium. This study suggested that the mutant, RM2-24 has L-LDH gene which is expressed in presence of (NH4)(2)HPO4 resulting in L-lactic acid production. Co-production of L-lactic acid in D-lactic acid fermentation may be detrimental in the PLA production. (C) 2017, The Society for Biotechnology, Japan. All rights reserved.