Wastewater treatment plants generate municipal sewage sludge as a by-product of biological wastewater treatment. Activated sludge has been drawing attention because of its capability to produce microbial lipids, which can be used as a precursor for alternative biofuels production or as an oleochemical feedstock. However, microbial biomass cultivation for lipid production is primarily influenced by substrate utilization of microorganisms which typically depends on expensive sugar-based feedstocks. Current studies have shown the potential of natural microbial consortium to convert methane into valuable products via biochemical processes. Methanotrophs are aerobic microorganisms which are naturally present in a variety of environments including wastewater treatment facilities. They have the unique ability to utilize methane as their sole carbon and energy source hence they are considered as important candidate for methane bioconversion to produce broad types of valuable bio-products like lipids. Optimizing the cultivation conditions for attaining high productivity and bioconversion efficiency is a critical step for the development of an economically viable bioreactor for commercialization. Therefore, this study aimed to test the optimum conditions achieved from a previous study via scaling up in 5-L reactors to maximize methane consumption, methanotrophs’ growth, and lipid production. In this work, natural microbial consortia were collected from the East Wastewater Treatment Plant in Lafayette, LA. The optimum ammonium and copper concentrations used were 1,043 mg/L and 0 mg/L, respectively. Methane to air volume ratio was set at 1:4 and was replenished every other day. Methane consumption was determined via gas chromatography analysis of headspace gases. Freeze drying and accelerated solvent extraction were done to measure the biomass concentration and lipid yield, while DNA extraction followed by 16S rRNA analysis was performed to monitor methanotrophs’ growth. These results prove the scalability of methanotrophs cultivation using the optimized conditions to enhance methane consumption, methanotrophs’ growth, and lipid production. Moreover, the conclusions highlight the potential of natural microbial consortia to convert methane into lipids as well as the feasibility of using an actual wastewater as medium for cultivating methanotrophs.
