1-18: Draft genome sequence reveals insights into the H2 metabolism of Caloramator celere

Tuesday, May 1, 2012
Napoleon Ballroom C-D, 3rd fl (Sheraton New Orleans)
Alessandro Ciranna1, Antti Larjo2, Ville Santala1, Christophe Roos2 and Matti Karp1, (1)Department of Chemistry and Bioengineering, Tampere University of Technology, Tampere, Finland, (2)Department of Signal Processing, Tampere University of Technology, Tampere, Finland
Caloramator celere (former Thermobrachium celere) is an anaerobic alkalithermophilic bacterium able to covert sugars to H2, CO2, acetate, ethanol and formate. Thanks to its ability to rapidly grow in an extremely selective environment (doubling time=10 min; Topt=67°C; pH67°C opt=8.2) it might be a promising candidate for biohydrogen production in open (non-sterile) systems.

The whole genome of C. celere was recently sequenced generating a draft genome sequence consisting of 43 scaffolds with a total assembly size of 2.32 Mb (G+C content of 31%) and containing 2260 coding sequences.

Bioinformatic analyses revealed genes encoding key enzymes involved in pyruvate catabolism pathways. At pyruvate node one putative pyruvate:formate lysase (potentally activated by three putative pyruvate:formate

lyase activating enzymes) and two putative pyruvate:ferredoxin oxidoreductases catalyze the conversion of pyruvate to acetyl-CoA. Two putative NADH-dependent FeFe-hydrogenases and one putative ferredoxin-dependent membrane bound NiFe-hydrogenase are involved in the regeneration of NAD+ and oxidized ferredoxin through proton reduction with consequent H2 synthesis.  Alternatively, regeneration of NAD+ can be carried out by conversion of acetyl-CoA to ethanol by two putative alcohol dehydrogenases.

Experimental results showed that carbon and electron flow distributions were affected by the feedback inhibition caused by H2 accumulation. When the PH2 was kept under 23 kPa by nitrogen sparging of culture headspace H2 production by C. celere yielded 3.53 mol-H2/mol-glucose with a remarkable maximum H2 production rate of 41.5 mmol-H2/l/h.

Genetic information, together with experimental data, outlined the possible metabolic scenario for H2 synthesis, highlighting potential process improvements to enhance H2 production from C. celere.

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