Production of Biohydrogen and/or Poly-?-hydroxybutyrate by Rhodopseudomonas sp. Using Various Carbon Sources as Substrate

The polyhydroxyalkanoates (PHA) are family of biopolyesters synthesized by numerousbacteria which are attracting a great attention due to their thermoplastic properties.Polyhydroxybutyrate (PHB) is the most common type of PHA which presents thermoplastic and biodegradable properties. It is synthesized under stressful conditions byheterotrophic bacteria and many photosynthetic microorganisms such as purple nonsulfur bacteria and cyanobacteria. Biological hydrogen (H2) production is being evaluatedfor use as a fuel since it is a promising substitute for carbonaceous fuels owing to its highconversion efficiency and high specific content. In the present work, the purple non-sulfurphotosynthetic bacterium Rhodopseudomonas sp. for the simultaneous H2 photoevolution and poly-?-hydroxybutyrate (PHB) production has been investigated. Threedifferent types of carbon sources were tested in the presence of glutamate as a nitrogensource in a batch cultivation system, under continuous irradiance. The results indicatedthe fact that the type of carbon source in the culture broth affects in various ways themetabolic activity of the bacterial biomass, as evidenced by the production of PHB and/orH2 and biomass. The best carbon source for PHB accumulation and H2 production byRhodopseudomonas sp. turned out to be the acetate, having the highest H2 production(2286 mL/L) and PHB accumulation (68.99 mg/L, 18.28% of cell dry weight).