Expression of Heterologous PEP Carboxylase in Methylococcus capsulatus MIR: Effect on Growth Parameters and Amino Acid Composition of the Biomass

Methylococcus capsulatus MIR is a strain of methanotrophic bacteria that is potentially suitable for production of feed protein and other value-added compounds from methane. Genomic analysis did not reveal in Mc. capsulatus MIR any known pathways of C3-carboxylation necessary for the replenishment of the tricarboxylic acid cycle intermediates and the full-scale metabolic functioning. The pepc gene encoding PEP carboxylase in Methylomonas rapida 12 was introduced into Mc. capsulatus MIR cells on a plasmid under the control of a medium-strength promoter. Expression of heterologous PEP carboxylase led to an increase in the content of glutamate, glycine, and lysine in the cells of the recombinant strain, but did not increase the growth rate of the culture. Consequently, the introduction of heterologous PEP carboxylase, which carries out the C3-carboxylation reaction, helps to increase the nutritional value of the methanotroph biomass.