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Glutamate and histidine improve both solvent yields and the acid tolerance response of Clostridium beijerinckii NCP 260
Author(s) -
Reeve B.W.P.,
Reid S.J.
Publication year - 2016
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.13067
Subject(s) - clostridium beijerinckii , chemistry , clostridium , histidine , solvent , biochemistry , food science , biology , bacteria , amino acid , genetics
Aims This study aims to examine the effect of amino acid supplementation on solvent production by Clostridium beijerinckii during the acetone‐butanol fermentation and to determine whether amino acids are involved in the acid tolerance response (ATR), which results in increased solvents. Methods and Results Fermentation studies with Cl. beijerinckii NCP 260 in limited‐nitrogen media supplemented with glutamate, glutamine, lysine, proline, histidine or asparagine revealed that only glutamate, glutamine or histidine increased butanol titres comparable to control media. Acid survival tests at pH 5 showed that glutamate and histidine were effective in protecting Cl. beijerinckii cells against acid shock, and may be involved in the ATR. Using quantitative PCR, the transcription of the glutamine synthetase, nitrogen regulator and glutamate synthase operon ( glnA‐nitR‐gltAB ) was monitored during acid shock conditions, and expression of both the nitR and gltA genes was shown to be increased twofold. Conclusions Glutamate and histidine specifically enhance the ATR in Cl. beijerinckii NCP 260, and the genes encoding glutamate synthase and the NitR regulator are both upregulated, predicted to lead to increased endogenous glutamate pools during acidogenesis. This may enhance the ATR and allow more viable cells to enter solventogenesis, thereby increasing butanol titres. Glutamine, glutamate and histidine may also afford protection from butanol stress directly. Significance and Impact of the Study Using substrates naturally rich in glutamine, glutamate and histidine in industrial fermentations is a promising means to increase acid survival and solvent yields in solventogenic Clostridium .