Project description:In this study we investigated the steady-state growth of Methylotuvimicrobium alcaliphilum 20ZR in media containing calcium (Ca) or lanthanum (La, a REE element). RNA-seq profiling of Methylomicrobium alcaliphilum strain 20ZR in bioreactor on methane. Sample cultures, La-optimum, La-CH4 limited, Ca-optimum and Ca-CH4 limited, were collected and immediately transferred into tubes containing 5 ml of the stop solution (5% water-equilibrated phenol in ethanol). It was found, that cells supplemented with La show a higher growth rate compared to Ca-cultures; however, the efficiency of carbon conversion, estimated as biomass yield, is higher in cells grown with Ca. The study was financially supported by DOE under FOA DE-FOA-0001085 and by NSF-CBET award 1605031
Project description:Rhamnolipids (RL) are well-studied biosurfactants naturally produced by pathogenic strains of P. aeruginosa. Current methods to produce RLs in native and heterologous hosts have focused on carbohydrates as production substrate; however CH4 provides an intriguing alternative as a substrate for RL production because it is low-cost and may mitigate greenhouse gas emissions. Here we demonstrate RL production from CH4 by Methylotuvimicrobium alcaliphilum 20Z. RLs were inhibitory to M. alcaliphilum growth at low concentrations (<0.05 g/L), so adaptive evolution was performed by growing M. alcaliphilum in increasing concentrations of RLs, producing a strain that grew in the presence of 5 g/L of RLs. Metabolomics and proteomics of the adapted strain grown on CH4 in the absence of RLs revealed metabolic changes increase in fatty acid production and secretion, alterations in gluconeogenesis, and increased secretion of lactate and osmolyte products compared to the parent strain. Expression of plasmid-borne RL production genes in the parent M. alcaliphilum strain resulted in cessation of growth and cell death. In contrast, the adapted strain transformed with the RL production genes showed no growth inhibition and produced up to 1 M of RLs, a 600-fold increase compared to the parent strain. This work has promise for developing technologies to produce fatty acid-derived bioporducts, including biosurfactants, from CH4.
