Enhanced photo-fermentative hydrogen production by Rhodobacter capsulatus with pigment content manipulation.

High content of pigment in purple nonsulfur photosynthetic bacteria hinders its photo-hydrogen production rate under intense light irradiation. In order to alleviate the light shielding effect and improve its photo-fermentative hydrogen production performance, pufQ, which is the regulatory gene of bacteriochlorophyll biosynthesis in Rhodobacter capsulatus, was cloned and relocated in the genome under cbb3 promoter by homologous recombination. The UV-vis spectra indicated that the light absorption of the mutant between 300 and 900 nm was reduced. Photo-hydrogen production experiments by the recombinant and wild type strain were carried out in 350 mL photo bioreactors using acetic and butyric acid as substrate. The results showed that the hydrogen production of recombinant with reduced pigment was 27% higher than that of its parental strain, indicating that it is effective on enhancing photo-fermentative hydrogen production by manipulating pigment biosynthesis in purple nonsulfur photosynthetic bacteria.