Berkeley Lab-led team re-engineering new enzyme and metabolic cycle for direct production of liquid transportation fuels from methane
16 January 2014
A Berkeley Lab-led team is working to re-engineer an enzyme for the efficient conversion of methane to liquid hydrocarbon transportation fuels. The project was awarded $3.5 million by the Advanced Research Projects Agency - Energy (ARPA-E) as part of its REMOTE (Reducing Emissions using Methanotrophic Organisms for Transportation Energy) program. (Earlier post.)
Methane can be converted to liquid hydrocarbons by thermochemical processes; however, these processes are both energy intensive and often non-selective. There are bacteria in nature—methanotrophs—that consume methane and convert it to chemicals that can be fashioned into fuel. Unfortunately, the enabling enzyme doesn’t produce chemicals with the efficiency needed to make transportation fuels. While some scientists are working to make this enzyme more efficient, Dr. Christer Jansson’s team is taking a new approach by starting with a different enzyme that ordinarily takes in carbon dioxide.
The structure of this enzyme is relatively simple and well understood, making it an ideal platform with which to tinker—in this case meaning engineering the enzyme to consume methane instead of carbon dioxide and release a product that can feed into a pathway for fuel synthesis.
This new enzyme, a methylase, could be added to bacteria for production of different fuels such as butanol and biodiesel. In practice, these specially designed bacteria would be placed in a bioreactor.
John Tainer’s and Steve Yannone’s groups in Berkeley Lab’s Life Sciences Division will explore how the enzyme can be tweaked so that it binds with methane. They’ll use computational analysis to map the structural changes needed so that the enzyme can break methane’s bonds. They’ll also study the enzyme at Berkeley Lab’s Advanced Light Source, where the SIBYLS synchrotron beamline combines X-ray scattering with X-ray diffraction capabilities. This will help the scientists determine the enzyme’s functional 3-D structure.
In addition, Novici Biotech, a California-based industrial partner, will create tens of thousands of variants of the enzyme with its proprietary synthetic biology technology. Romy Chakraborty of Berkeley Lab’s Earth Sciences Division and scientists from the US Department of Energy’s Joint BioEnergy Institute will assist in analyzing these variants to identify those with the best characteristics.
Ideally, each step will circle closer to a new enzyme that’s very efficient at converting methane to an oxidized product.
Once a functional methylase has been constructed, we need to engineer a new metabolic cycle that takes up methane and regenerates the co-substrate. Just like the Calvin-Benson cycle, but with assimilation of methane instead of carbon dioxide. This will take some time, but if we’re successful, the methylase can be installed into various microorganisms such as E. coli, yeast, and cyanobacteria and used on a large scale to produce liquid fuel from methane in natural gas or other sources.
—Christer Jansson
Two other industrial partners, Kiverdi, Inc. and Microvi Biotechnologies, are also involved in the project to optimize gas bioprocessing and other culture conditions for growing the engineered cells. Kiverdi is also heading the business analysis and tech transfer part of the project with Berkeley Lab business specialists Andrea Schoeller and Bill Shelander.
The Advanced Light Source is a third-generation synchrotron light source producing light in the x-ray region of the spectrum that is a billion times brighter than the sun.
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