Improved growth rate in Clostridium thermocellum hydrogenase mutant via perturbed sulfur metabolism. Issue 1 (December 2017)

• Record Type: Journal Article
• Authors: Biswas, Ranjita; Wilson, Charlotte; Giannone, Richard; Klingeman, Dawn; Rydzak, Thomas; Shah, Manesh; Hettich, Robert; Brown, Steven; Guss, Adam
• Is Part Of: Biotechnology for biofuels. Volume 10:Issue 1(2017)
• Page Start: 1
• Page End: 10
• Publication Date: 2017-12
• Subjects: Cellulosic ethanol -- Clostridium thermocellum -- Redox balance -- Metabolic engineering -- Sulfate reduction; Biotechnology -- Periodicals; Biomass energy -- Periodicals; Energy-Generating Resources -- Periodicals; 662.88
• DOI: 10.1186/s13068-016-0684-x
• Languages: English
• ISSNs: 1754-6834

Abstract

Abstract Background Metabolic engineering is a commonly used approach to develop organisms for an industrial function, but engineering aimed at improving one phenotype can negatively impact other phenotypes. This lack of robustness can prove problematic. Cellulolytic bacteriumClostridium thermocellum is able to rapidly ferment cellulose to ethanol and other products. Recently, genes involved in H2 production, including the hydrogenase maturasehydG and NiFe hydrogenaseech, were deleted from the chromosome ofC. thermocellum . While ethanol yield increased, the growth rate of ΔhydG decreased substantially compared to wild type. Results Addition of 5 mM acetate to the growth medium improved the growth rate inC. thermocellum ∆hydG, whereas wild type remained unaffected. Transcriptomic analysis of the wild type showed essentially no response to the addition of acetate. However, inC. thermocellum ΔhydG, 204 and 56 genes were significantly differentially regulated relative to wild type in the absence and presence of acetate, respectively. Genes, Clo1313_0108-0125, which are predicted to encode a sulfate transport system and sulfate assimilatory pathway, were drastically upregulated inC. thermocellum ΔhydG in the presence of added acetate. A similar pattern was seen with proteomics. Further physiological characterization demonstrated an increase in sulfide synthesis and elimination of cysteine consumption inC. thermocellum ΔhydG .Clostridium thermocellum ΔhydGΔech had a higher growth rate thanΔhydG in the absence of added acetate, and a similar but less pronounced transcriptional and physiological effect was seen in this strain upon addition of acetate. Conclusions Sulfur metabolism is perturbed inC. thermocellum ΔhydG strains, likely to increase flux through sulfate reduction to act either as an electron sink to balance redox reactions or to offset an unknown deficiency in sulfur assimilation.