Enhancement of photohydrogen production using phbC deficient mutant Rhodopseudomonas palustris strain M23

This study used a DNA recombination method to knock out the poly-β-hydroxybutyrate (PHB) synthesis gene phbC in the photosynthetic bacterium Rhodopseudomonas palustris WP3-5. The experimental results indicated that the mutant strain Rps. palustris M23 could be successfully screened. Fluorescent observation with Nile blue staining showed no significant PHB granule accumulation in the mutant cells. Batch mode experiments using acetic acid as a carbon source revealed a 29.1% and 25.9% hydrogen gas content from M23 and WP3-5, respectively. However, this trend did not appear when using propionic acid as carbon source. Under continuous operation, the hydrogen gas content from M23 could be maintained above 72%. The average hydrogen production rates of the WP3-5 and M23 strains were 264 mL-H2/L/day and 457 mL-H2/L/day, respectively. The total biogas volume collected from M23 was 1.7 times higher than that from the wild type.