Enhancing D-lactic acid production from methane through metabolic engineering of Methylomonas sp. DH-1

BACKGROUND: Methane is an abundant and low-cost carbon source with great potential for conversion into value-added chemicals. Methanotrophs, microorganisms that utilize methane as their sole carbon and energy source, present a promising platform for biotechnological applications. This study aimed to engineer Methylomonas sp. DH-1 to enhance D-LA production through metabolic pathway optimization during large-scale cultivation. RESULTS: In this study, we regulated the expression of D-lactate dehydrogenase (D-LDH) using a Ptac promoter with IPTG induction to mitigate the toxic effects of lactate accumulation. To further optimize carbon flow away from glycogen, the glgA gene was deleted. However, this modification led to growth inhibition, especially during scale-up, likely due to the accumulation of ADP-glucose caused by the rewired carbon flux under carbon-excess conditions. Deleting the g…