(67f) Evaluation of the Effects of Ammonium and Copper on Methanotrophs Growth and Activity for Lipid Production

Energy security and environmental concerns due to global warming have driven the continuous quest for clean, reliable, and efficient energy sources, as well as the pursuit for cost-effective technologies to reduce greenhouse gas emissions (GHGs). Natural gas is a fossil energy source primarily used to generate electricity (electric power sector), for heating (residential and commercial sectors) or as fuel (industrial and transportation sectors). Natural gas is mainly composed of methane. Methane, as the second most abundant GHG, is 28 times more potent than carbon dioxide. Despite its prevalence, natural gas is vented and flared into the atmosphere because of its historically low and volatile prices over the past decade, resulting in both product and energy losses along with major GHG emissions. In support of the Global Methane Pledge for climate change mitigation, the United States Environmental Protection Agency proposed a new Clean Air Act rule that would lead to significant, cost-effective reductions in methane emissions. One of the promising solutions is the conversion of methane into value-added products with a high profit margin. Methanotrophs are gaining interests due to their ability to utilize methane as their sole carbon and energy source to produce a wide variety of bio-products such as lipids. These bacteria are naturally present in a variety of environment such as wetlands, paddies, sediments, landfills, and waste treatment facilities. Various types of methanotrophs respond differently to changing environmental conditions. The knowledge on the behavior of methanotrophs under varying conditions is crucial for choosing the suitable type of methanotrophs for culture enrichment and cultivation optimization tailored for producing a certain bio-product. Copper and ammonium play key roles in the physiology and activity of methanotrophs. Therefore, this study aimed to evaluate the influence of ammonium and copper on methane consumption and methanotrophs growth to optimize lipid production. In this work, natural microbial consortia were collected from the East Wastewater Treatment Plant and were subjected to DNA extraction followed by 16S rRNA analysis to determine the identity and relative abundance of their microbial population. Growth parameters were varied to study the effects of ammonium (0 and 1,070 mg/L) and copper (0 and 4.49 mg/L) on the conversion of methane to lipids. A 2k full factorial design of experiment was employed to verify the best conditions for methane consumption and lipid production. Methane consumption was monitored via gas chromatography analysis of the headspace gases. Freeze drying and accelerated solvent extraction were done to measure the biomass concentration and lipid yield. After 18 days of incubation, results show that the highest % methane consumption, biomass concentration, and % lipid production were 1.74%, 7,074.93 mg/L, and 66.51%, respectively at different conditions. These findings provide the optimum conditions for methanotrophs cultivation for the production of lipids. Moreover, the conclusions highlight the potential of natural microbial consortia to convert methane into lipids that could address concerns on GHG emission as well as for value-added resources recovery.