Methane is an important feedstock for the bioeconomy since it is abundant and inexpensive. The bacteria that grow on methane (methanotrophs) are well-known with excellent genetic and genomic tools. Several examples exist of value-added products from engineered methanotrophs, such as carotenoids, fatty acids, succinate, lactate, and propanediol, and natural gas-derived single cell protein (SCP) for aquaculture is currently marketed by multiple companies. However, natural gas should be directed to use for energy and it is not advantageous to divert natural gas streams to the bioeconomy. Instead, stranded methane (methane too dilute for use as natural gas) is an attractive alternative feedstock. It is estimated that this source accounts for over 200 million tons of methane per year, and currently there are few commercial technologies able to take advantage of this large feedstock due to the low concentration. Biological conversions have specific advantages over chemical conversions in this context: a) able to utilize low feedstock concentrations; b) amenable to low CapEx and OpEx processes, enabling targeting of relatively small sources; and c) generation of minimal toxic wastes, keeping costs low. In order to reach the potential of biological processes using stranded methane as a feedstock, it is necessary to develop technologies that maximize usage of methane at low concentrations, preferably below 1%, to take advantage of the maximum number of stranded methane sources.
We have identified a methanotroph in our culture collection that is especially adept at consuming methane at low concentrations. This strain, Methylotuvimicrobium buryatense 5GB1C shows the highest rates of methane consumption in the literature at concentrations between 0.01 and 0.5% (100-5000 ppm). We have tested numerous targeted approaches to increase growth and methane consumption ability in this strain at low methane concentrations, and these are ongoing. Using adaptive lab evolution, we now have isolates that utilize low methane at ~2-fold the rate of the wild-type, giving a significant boost to the biocatalyst activity. We continue to use directed and evolved strain approaches to improve performance at low methane.
The ability to take advantage of the 200 million tons of wasted carbon feedstock annually will allow generation of high value bioproducts that could not be generated by alternative approaches. Initially, the target will be SCP for aquaculture, but the long-term goal is to generate higher value products such as carboxylic acids and carotenoids. The combination of the new methanotroph variant with such products predicts profitability, based on a preliminary technoeconomic analysis. In addition, the decreased ozone in the surrounding areas will create health benefits