Selective production of acetone during continuous synthesis gas fermentation by engineered biocatalyst Clostridium sp. MAceT113

Abstract

Aims: To engineer acetogen biocatalyst capable of fermenting synthesis gas blend to acetone as the only liquid carbonaceous product. Methods and Results: The metabolic engineering comprised inactivation of phosphotransacetylase via integration of a cassette comprising synthetic genes erm(B), thiolase and HMG‐CoA synthase. Acetaldehyde dehydrogenase was inactivated via integration of a cassette consisting of synthetic genes cat, HMG‐CoA lyase and acetoacetate decarboxylase. The engineered biocatalyst Clostridum sp. MAceT113 lost production of 253 mmol l−1 ethanol and 296 mmol l−1 acetate and started producing 1·8 mol l−1 acetone in single‐stage continuous syngas fermentation. Conclusions: The acetone concentration in culture broth is economical for bulk manufacture because it is about twenty times of that achieved with known acetone–butanol–ethanol fermentation of sugars. Significance and Impact of the Study: The process shows the opportunity to produce acetone from synthesis gas at concentrations comparable with production of acetone from products of petroleum cracking. This is the first report on elimination of acetate and acetaldehyde production and directing carbon flux from Acetyl‐CoA to acetone via a non‐naturally occurring in acetogen acetone biosynthesis pathway identified in eukaryotic organisms.

Trash to treasure: production of biofuels and commodity chemicals via syngas fermenting microorganisms

“…Recently, Tyrurin and coworkers reported in a series of publications on completely abolishing acetate production in an undisclosed Clostridium strain, in favor of acetone [75], ethanol [76,77], butanol [78], mevalonate [78], methanol, or formate [79] production during autotrophic growth on syngas. However, eliminating acetate synthesis by deletion of the phosphotransacetylase and/or acetate kinase (ack) genes presumably prevents the concurrent synthesis of ATP (via SLP) by Ack.…”

Expression of amplified synthetic ethanol pathway integrated usingTn7-tool and powered at the expense of eliminatedpta,ack,spo0A and spo0J during continuous syngas or CO2/H2blend fermentation

“…The syngas blend composition was elaborated based on reported earlier empirical stoichiometry of the process (Berzin and Tyurin ; Berzin et al . ; Tyurin et al . ).…”

“…; Berzin et al . ,b). Primers specific to detect the expression of cat , ack, pta , spo A 1 , spo A 2 , spo 0J 1 , spo 0J 2 and al‐adh (Table ) in the respective intermediate recombinants or the finalized biocatalysts were used where appropriate.…”

“…Engineered biocatalysts can ferment CO 2 ‐rich syngas or captured CO 2 with zero CO 2 process vent gas emissions to the target product when inexpensive H 2 source is available (water hydrolysis using electricity produced by DOE recommended high‐efficiency solar panels in situ ) (Berzin et al . ).…”

“…As no known commercial biocatalysis utilizes naturally occurring strains, metabolic engineering renders new synthetic pathways stably functional in engineered biocatalyst micro‐organisms where the proper management of cell energy pool has been elaborated (Berzin et al . ,b).…”