Genome-Scale Metabolic Network Reconstruction and In Silico Analysis of Hexanoic acid Producing <i>Megasphaera elsdenii</i>

• Main Authors: Na-Rae Lee, Choong Hwan Lee, Dong-Yup Lee, Jin-Byung Park
• Format: Article
• Language: English
• Published: MDPI AG 2020-04-01
• Series: Microorganisms
• Subjects: <i>Megasphaera elsdenii</i>; hexanoic acid; bifurcated pathway; genome-scale metabolic model; constraint-based modeling
• Online Access: https://www.mdpi.com/2076-2607/8/4/539

Hexanoic acid and its derivatives have been recently recognized as value-added materials and can be synthesized by several microbes. Of them, <i>Megasphaera elsdenii</i> has been considered as an interesting hexanoic acid producer because of its capability to utilize a variety of carbons sources. However, the cellular metabolism and physiology of <i>M. elsdenii</i> still remain uncharacterized. Therefore, in order to better understand hexanoic acid synthetic metabolism in <i>M. elsdenii</i>, we newly reconstructed its genome-scale metabolic model, <i>i</i>ME375, which accounts for 375 genes, 521 reactions, and 443 metabolites. A constraint-based analysis was then employed to evaluate cell growth under various conditions. Subsequently, a flux ratio analysis was conducted to understand the mechanism of bifurcated hexanoic acid synthetic pathways, including the typical fatty acid synthetic pathway via acetyl-CoA and the TCA cycle in a counterclockwise direction through succinate. The resultant metabolic states showed that the highest hexanoic acid production could be achieved when the balanced fractional contribution via acetyl-CoA and succinate in reductive TCA cycle was formed in various cell growth rates. The highest hexanoic acid production was maintained in the most perturbed flux ratio, as phosphoenolpyruvate carboxykinase (<i>pck</i>) enables the bifurcated pathway to form consistent fluxes. Finally, organic acid consuming simulations suggested that succinate can increase both biomass formation and hexanoic acid production.