Chitosan/oleamide nanofluid as a significant medium for enhancing gas utilization efficiency in C1-gas microbial biotransformation

Abstract

Microbial biotransformation of C1 gas feedstocks such as CH4 and CO is a notable technique for sustainable, carbon–neutral chemical and fuel production. However, low C1-gas utilization efficiency in biological processes has hampered the efficient production of value-added materials, despite efficient, nonnative strains having been recently developed. Here, we constructed a nanofluid material mainly composed of chitosan and oleamide (CS/OA), which was stably suspended with a particle size of 120.7 ± 39.0 nm in aqueous culture media below pH 7.5 and attached to the cell surface, leading to a change in hydrodynamic properties mainly due to the decrease of surface tension and a decrease in mass-transfer resistance on the cell surface. The nanofluid was applied to three C1-gas-utilizing strains, Methylomonas sp. DH-1 (a type I methanotroph), Methylosinus trichosporium OB3b (a type II methanotroph), and Thermococcus onnurineus NA1 156 T (a hyperthermophilic CO-utilizing archaeon). Changes in culture media and cell membranes from the applied CS/OA nanoparticles increased specific cell growth rates (μmax). Remarkably, the strains adapted from the seed culture using the CS/OA nanofluid media also had increased μmax in a subsequent subculture and the main culture using conventional culture media, resulting in higher C1 gas consumption, cell growth, and metabolite production, such as succinate production. These results showed that the CS/OA nanofluid could be an effective medium to increase gas utilization efficiency and cell growth, and it is expected that the nanofluid can be widely used for increasing the production of value-added metabolites in C1-gas microbial biotransformation.