Engineering of Corynebacterium glutamicum For the Secretion of Lignin-modifying Enzymes

Lignin is a naturally abundant source of aromatic carbon but is largely underutilized inindustry because it is difficult to decompose. Recent research activity has targeted the development of a biological platform for the conversion of lignin and lignin-derived feedstock. Corynebacterium glutamicum is a standout candidate for the bacterial depolymerization and assimilation of lignin because of its performance as an industrial producer of amino acids, resistance to aromatic compounds in lignin, and low extracellular protease activity. Under the current study, nine experimental strains of C. glutamicum were engineered with sequencing-confirmed plasmids to overexpress and secrete lignin-modifying enzymes with the eventual goal of using lignin as raw feed for the sustainable production of valuable chemicals. Within the study, laccase and peroxidase activity were discovered to be decreased in C. glutamicum culture media. For laccase the decrease reached statistical significance, with an activity of about 10.9 U/L observed in water but only about 7.56 U/L and 7.42 U/L in fresh and spent BHI media, respectively, despite the same amounts of enzyme being added. Hypothesized reasons for this inhibitory effect are discussed here, but further work is needed to identify causative factors and realize the potential of C. glutamicum for waste biomass valorization.