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Mechanism of the oxidative stress‐mediated increase in lipid accumulation by the bacterium, R. opacus PD630: Experimental analysis and genome‐scale metabolic modeling
Author(s) -
Sundararaghavan Archanaa,
Mukherjee Amitava,
Sahoo Swagatika,
Suraishkumar G. K.
Publication year - 2020
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.27330
Subject(s) - pentose phosphate pathway , aconitase , biochemistry , citric acid cycle , flux (metallurgy) , glycolysis , enzyme , dehydrogenase , chemistry , triosephosphate isomerase , oxidative stress , bacteria , oxidative phosphorylation , biology , genetics , organic chemistry
Appropriate species of oleaginous bacteria, with their high growth rates and lipid accumulation capabilities, can be good contenders for industrial triacylglycerol (TAG) production, compared to microalgae. Further, oxidative stress (OS) can be used to significantly increase TAG yields in oleaginous microbes, but the mechanism is unexplored. In a first, this study explored the mechanism behind OS‐mediated increase in TAG accumulation by the bacterium, Rhodococccus opacus PD630, through experimental analysis and metabolic modelling. Two mechanisms that could increase acetyl‐CoA (TAG‐precursor) levels were hypothesized based on literature information. One was OS‐mediated inactivation of the aconitase (TCA cycle), and another was the inactivation of the triosephosphate isomerase (TPI; glycolysis). The results negated the involvement of aconitase in increased acetyl‐CoA levels. Analysis of the metabolic model showed that inactivation of TPI, re‐routed the flux through the pentose phosphate pathway (PPP), supplying both NADPH and acetyl‐CoA for TAG synthesis. Additionally, inactivation of TPI increased TAG flux by 143%, whereas, inactivating both TPI and aconitase, increased it by 152%. We present experimental evidence for OS‐mediated decrease in TPI activity and increase in activity of glucose‐6‐phosphate dehydrogenase (PPP enzyme). The findings indicate that increased flux through PPP can be explored to improve TAG accumulation on a large‐scale.