Metabolic engineering of Caldicellulosiruptor bescii yields increased hydrogen production from lignocellulosic biomass

Journal Article · Tue Jan 01 04:00:00 EST 2013 · Biotechnology for Biofuels

DOI:https://doi.org/10.1186/1754-6834-6-85· OSTI ID:1087053

Cha, Minseok ^[1]; Chung, Daehwan ^[1]; Elkins, James G ^[2]; Guss, Adam M ^[2]; Westpheling, Janet ^[1]

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1. University of Georgia, Athens, GA
2. ORNL

Background: Members of the anaerobic thermophilic bacterial genus Caldicellulosiruptor are emerging candidates for consolidated bioprocessing (CBP) because they are capable of efficiently growing on biomass without conventional pretreatment. C. bescii produces primarily lactate, acetate and hydrogen as fermentation products, and while some Caldicellulosiruptor strains produce small amounts of ethanol C. bescii does not, making it an attractive background to examine the effects of metabolic engineering. The recent development of methods for genetic manipulation has set the stage for rational engineering of this genus for improved biofuel production. Here, we report the first targeted gene deletion, the gene encoding lactate dehydrogenase (ldh), for metabolic engineering of a member of this genus. Results: A deletion of the C. bescii L-lactate dehydrogenase gene (ldh) was constructed on a non-replicating plasmid and introduced into the C. bescii chromosome by marker replacement. The resulting strain failed to produce detectable levels of lactate from cellobiose and maltose, instead increasing production of acetate and H2 by 21-34% relative to the wild type and pyrFA parent strains. The same phenotype was observed on a real-world substrate switchgrass (Panicum virgatum). Furthermore, the ldh deletion strain grew to a higher maximum optical density than the wild type on maltose and cellobiose, consistent with the prediction that the mutant would gain additional ATP with increased acetate production. Conclusions: Deletion of ldh in C. bescii is the first use of recently developed genetic methods for metabolic engineering of these bacteria. This deletion resulted in a redirection of electron flow from production of lactate to acetate and hydrogen. New capabilities in metabolic engineering combined with intrinsic utilization of lignocellulosic materials position these organisms to provide a new paradigm for consolidated bioprocessing of fuels and other products from biomass.

• Research Organization: Oak Ridge National Laboratory (ORNL)
• Sponsoring Organization: SC USDOE - Office of Science (SC)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1087053
• Journal Information: Biotechnology for Biofuels, Journal Name: Biotechnology for Biofuels Journal Issue: 1 Vol. 6; ISSN 1754-6834
• Country of Publication: United States
• Language: English

Related Subjects

Biohydrogen
Caldicellulosiruptor
Metabolic engineering
Switchgrass
ldh