Metabolic Engineering of Gas Fermenting Organisms for Commercial Scale Production of Fuels and Commodity Chemicals from Waste and Low Cost Resources

In December 2015, 195 countries adopted the Paris Agreement at the United Nations Climate Change Conference. The agreement “aims to strengthen the global response to the threat of climate change” and seeks to hold the increase in global average temperature to “well below 2°C above pre-industrial levels”. Though non-binding, this underscores the urgency for action that will radically limit global greenhouse gas emissions. Specifically, recent data indicates that this will require leaving a third of oil reserves, half of gas reserves, and over 80% of coal reserves unused until 2050.

LanzaTech has developed novel technology that recycles carbon from local, highly abundant, waste and low cost resources. The process converts gas containing carbon monoxide or CO₂ (e.g. from industrial sources like steel mills or processing plants) or syngas generated from any biomass resource (e.g. municipal solid waste, organic industrial waste or agricultural waste) into a range of sustainable fuels and commodities. Such feedstock flexibility and product diversification are important parts of ensuring favorable economics for this breakthrough technology.

At the heart of the process is a gas fermenting, acetogenic microbe Clostridium autoethanogenum that is able to autotrophically grow on a range of C1 substrates. This exceptional feedstock flexibility relies on unique redox chemistry and energy conservation mechanisms that do not exist in standard hosts such as E. coli or yeast. LanzaTech has evolved a high performing chassis strain through extensive natural selection and developed a complete genetic toolbox for the organism, including genome editing tools and a comprehensive genetic parts library.

In order to maximize the value that can be added to the array of gas resources the process can use as an input, LanzaTech has developed several lines of metabolically engineered strains. This includes strains with optimized flux and tolerance for native products ethanol or 2,3-butanediol, as well as strains for synthesis of an array of non-native products via both natural and synthetic routes. Examples include production of acetone, isopropanol or butanol via combinatorial testing and optimization of genes from the commercial ABE fermentation process. Yields and production rates achieved on gas have exceeded those of native producers utilizing sugars or published examples of E. coli or yeast engineered for these products. In addition, the company is working on novel synthetic routes to products including 1,3-butanediol, butadiene and isobutylene. Effective engineering of gas fermenting organisms requires a deep understanding of energy and redox metabolism which dictates the product spectrum and is vastly different between gas and sugar fermenting organisms. To guide the metabolic engineering efforts, we have developed a systems biology platform and a genome-scale model that has been validated against hundreds of fermentation runs.

Scalable reactor designs and optimized process chemistry ensure efficient, continuous, single-pass gas conversion. The process has been successfully scaled-up to fully integrated 100,000-gallon/year demonstration plants with over 40,000 hours on stream. Such diverse gas streams as by-product gases from steel making and syngas produced from gasified biomass or municipal solid waste. Currently, LanzaTech is constructing its first commercial plants in Belgium, China and Taiwan.