Enhancing photo-fermentative hydrogen production performance of Rhodobacter capsulatus by disrupting methylmalonate-semialdehyde dehydrogenase gene

The effects of mmsA disruption in Rhodobacter capsulatus SB1003 on the pigment content, poly-β-hydroxybutyrate (PHB) content and photo-fermentative hydrogen production were studied. A transposon mutant assigned ZY29 with mutation on mmsA and an mmsA partially deleted mutant assigned ZYDM9 (mmsA−) were obtained. The mutants showed reduced pigment and PHB content, and improved photo-fermentative hydrogen production performance. The hydrogen yield and maximum hydrogen production rate of ZYDM9 were 4675 ± 76 mL/L and 92.4 ± 2.6 mL/(Lh), which increased by 22.8% and 20% compared with that of the WT, respectively. In the meantime, its pigment and PHB content were 20.7 ± 0.1 nmol/mg and 54.5 ± 2.6 mg/g-dcw, which reduced by 34.2% and 43.4% compared with that of WT, respectively. The optimum parameters for hydrogen production were initial pH 7.0, carbon nitrogen ratio (g/g) 3.0:0.5, and light intensity 800 ± 35 W/m2.