BioChem - DOS

Reversing methanogenesis to capture methane for liquid biofuel precursors

Microbial cell factories

Soo, Valerie W. C.; McAnulty, Michael J.; Tripathi, Arti; Zhu, Fayin; Zhang, Limin; Hatzakis, Emmanuel; Smith, Philip B.; Agrawal, Saumya; Nazem-Bokaee, Hadi; Gopalakrishnan, Saratram; Salis, Howard M.; Ferry, James G.; Maranas, Costas D.; Patterson, Andrew D.; Wood, Thomas K.

<P><B>Background</B></P><P>Energy from remote methane reserves is transformative; however, unintended release of this potent greenhouse gas makes it imperative to convert methane efficiently into more readily transported biofuels. No pure microbial culture that grows on methane anaerobically has been isolated, despite that methane capture through anaerobic processes is more efficient than aerobic ones.</P><P><B>Results</B></P><P>Here we engineered the archaeal methanogen <I>Methanosarcina acetivorans</I> to grow anaerobically on methane as a pure culture and to convert methane into the biofuel precursor acetate. To capture methane, we cloned the enzyme methyl-coenzyme M reductase (Mcr) from an unculturable organism, anaerobic methanotrophic archaeal population 1 (ANME-1) from a Black Sea mat, into <I>M. acetivorans</I> to effectively run methanogenesis in reverse. Starting with low-density inocula, <I>M. acetivorans</I> cells producing ANME-1 Mcr consumed up to 9&nbsp;±&nbsp;1&nbsp;% of methane (corresponding to 109&nbsp;±&nbsp;12&nbsp;&micro;mol of methane) after 6&nbsp;weeks of anaerobic growth on methane and utilized 10&nbsp;mM FeCl<SUB>3</SUB> as an electron acceptor. Accordingly, increases in cell density and total protein were observed as cells grew on methane in a biofilm on solid FeCl<SUB>3</SUB>. When incubated on methane for 5&nbsp;days, high-densities of ANME-1 Mcr-producing <I>M. acetivorans</I> cells consumed 15&nbsp;±&nbsp;2&nbsp;% methane (corresponding to 143&nbsp;±&nbsp;16&nbsp;&micro;mol of methane), and produced 10.3&nbsp;±&nbsp;0.8&nbsp;mM acetate (corresponding to 52&nbsp;±&nbsp;4&nbsp;&micro;mol of acetate). We further confirmed the growth on methane and acetate production using <SUP>13</SUP>C isotopic labeling of methane and bicarbonate coupled with nuclear magnetic resonance and gas chromatography/mass spectroscopy, as well as RNA sequencing.</P><P><B>Conclusions</B></P><P>We anticipate that our metabolically-engineered strain will provide insights into how methane is cycled in the environment by Archaea as well as will possibly be utilized to convert remote sources of methane into more easily transported biofuels via acetate.</P><P><B>Electronic supplementary material</B></P><P>The online version of this article (doi:10.1186/s12934-015-0397-z) contains supplementary material, which is available to authorized users.</P>

2016

BioMed Central

cc-by

1475-2859

15

pp.11

10.1186/s12934-015-0397-z

http://click.ndsl.kr/servlet/OpenAPIDetailView?keyValue=05787966&target=NART&cn=NART81075943

https://microbialcellfactories.biomedcentral.com/track/pdf/10.1186/s12934-015-0397-z

Reverse methanogenesis; Anaerobic oxidation of methane; Methyl-coenzyme M reductase