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M n 2+ and M g 2+ synergistically enhanced lactic acid production by L actobacillus rhamnosus FTDC 8313 via affecting different stages of the hexose monophosphate pathway
Author(s) -
Lew L.C.,
Choi S.B.,
Tan P.L.,
Liong M.T.
Publication year - 2014
Publication title -
journal of applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 1364-5072
DOI - 10.1111/jam.12399
Subject(s) - lactic acid , lactobacillus rhamnosus , biochemistry , dehydrogenase , hexose , chemistry , lactobacillus , enzyme , biology , bacteria , fermentation , genetics
Aims The study aimed to evaluate the effects of M n 2+ and M g 2+ on lactic acid production using response surface methodology and to further study their effects on interactions between the enzymes and substrates along the hexose monophosphate pathway using a molecular modelling approach. Methods and Results A rotatable central composite design matrix for lactic acid production was generated with two independent factors namely, manganese sulfate and magnesium sulfate. The second‐order regression model indicated that the quadratic model was significant ( P < 0·05), suggesting that the model accurately represented the data in the experimental region. Three‐dimensional response surface showed that lactic acid production was high along the region where the ratio of M n SO 4 to M g SO 4 was almost 1 : 1, justifying the need for both M g 2+ and M n 2+ to be present simultaneously in stimulating the production of lactic acid. Molecular docking simulation was performed on a total of 13 essential enzymes involved in the hexose monophosphate pathway for the production of lactic acid with four different conditions namely in the presence of M g 2+ , M n 2+ , both M g 2+ and M n 2+ and in the absence of metal ions. Results showed that the presence of both M g 2+ and M n 2+ within the binding site improved the binding affinity for substrates in five enzymes namely, glucose‐6‐phosphate dehydrogenase, phosphogluconate dehydrogenase, glyceraldehyde‐3‐phosphate dehydrogenase, phosphopyruvate hydratase and pyruvate kinase. Conclusions Using response surface methodology and molecular modelling approach, we illustrated that M g 2+ and M n 2+ synergistically enhanced lactic acid production by L actobacillus rhamnosus FTDC 8313 via affecting different stages of the hexose monophosphate pathway. Significance and Impacts of the Study M g 2+ and M n 2+ synergistically improved lactic acid production of L act. rhamnosus via improved binding affinity of the enzyme–substrate along the hexose monophosphate pathway, instead of purely affecting growth as previously understood.