OPTIMIZING ETHANOL PRODUCTION SELECTIVITY

Lactococcus Lactis metabolizes glucose homofermentatively to lactate.However, after disruption of the gene coding for lactate dehydrogenase, LDH -, a key enzyme in NAD+ regeneration, the glycolytic flux shifts from homolactic to mixed acid fermentation with the redirection of pyruvate towards production of formate, acetate, ethanol and carbon dioxide.A mathematical model of the pyruvate metabolism pathway that enhances our understanding of ethanol production was developed from in vivo nuclear magnetic resonance (NMR) time series measurements that describes the dynamics of the metabolites in L. lactis.An S-system model based on the power law representation was able to capture the observed dynamics of the pyruvate metabolism pathway in L. lactis in vivo.The model provides insights into the maximization of selectivity of ethanol with respect to acetate and carbon dioxide as undesired products in multiple reactions.High concentrations of NADH and acetyl-CoA and low concentrations of pyruvate and NAD appear to maximize ethanol selectivity.These conclusions help to design strategies for improvement of ethanol products from sugars or others biomass.The results bear relevance in the educational field due to its usefulness in metabolic engineering applications.