Flux balance analysis indicates that methane is the lowest cost feedstock for microbial cell factories

• Published in: Metabolic engineering communications Vol. 5; no. C; pp. 26 - 33
• Main Authors: Comer, Austin D., Long, Matthew R., Reed, Jennifer L., Pfleger, Brian F.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.12.2017; Elsevier
• Subjects: 09 BIOMASS FUELS; 60 APPLIED LIFE SCIENCES; acetates; bacteria; biorefining; carbon; carbon monoxide; energy; Escherichia coli; feedstocks; glucose; lignocellulose; liquids; market prices; metabolites; methane; methanol; natural gas; operating costs; Saccharomyces cerevisiae; Synechococcus; Synechococcus sp. PCC 7002; synthesis gas; transportation; yeasts
• ISSN: 2214-0301; 2214-0301
• DOI: 10.1016/j.meteno.2017.07.002

The low cost of natural gas has driven significant interest in using C1 carbon sources (e.g. methane, methanol, CO, syngas) as feedstocks for producing liquid transportation fuels and commodity chemicals. Given the large contribution of sugar and lignocellulosic feedstocks to biorefinery operating costs, natural gas and other C1 sources may provide an economic advantage. To assess the relative costs of these feedstocks, we performed flux balance analysis on genome-scale metabolic models to calculate the maximum theoretical yields of chemical products from methane, methanol, acetate, and glucose. Yield calculations were performed for every metabolite (as a proxy for desired products) in the genome-scale metabolic models of three organisms: Escherichia coli (bacterium), Saccharomyces cerevisiae (yeast), and Synechococcus sp. PCC 7002 (cyanobacterium). The calculated theoretical yields and current feedstock prices provided inputs to create comparative feedstock cost surfaces. Our analysis shows that, at current market prices, methane feedstock costs are consistently lower than glucose when used as a carbon and energy source for microbial chemical production. Conversely, methanol is costlier than glucose under almost all price scenarios. Acetate feedstock costs could be less than glucose given efficient acetate production from low-cost syngas using nascent biological gas to liquids (BIO-GTL) technologies. Our analysis suggests that research should focus on overcoming the technical challenges of methane assimilation and/or yield of acetate via BIO-GTL to take advantage of low-cost natural gas rather than using methanol as a feedstock. •Review of C1 assimilation strategies is presented.•Flux balance analysis used to create relative feedstock cost surfaces.•Methane found to be the lowest cost feedstock for conversion of C1 compounds.