The Study On Hydrogen Production Performance Of Rhodopseudomonas Palustris PB-Z

Hydrogen as a clean and renewable energy is considered as the most clean and promising alternative energy source in the furture. Among microbial processes, photofermentation is considered a promising and sustainable solution and can effectively combine organic wastewater treatment and hydrogen production. However, although qualitatively feasible, commercial exploitation of H2 requires quantitatively better yields.The effects of on the growth and hydrogen production of Rhodopseudomonas palustris PB-Z was studied, furthermore, part of the metabolic process was also discussed in this paper. The result showed that:（1） Stirring was favorable for bacterial growth and hydrogen production, but the effects of different mixing rate on the growth of PB-Z were the same, by contrast, the hydrogen production performances were affected greatly by the mixing rate. Under vigorous stirring（240 rpm）, the hydrogen production performances were greatly improved due to the hydrogen bubbles were immediately removed from the culture medium.（2） The wavelength of light had little influence on the growth of PB-Z, the ranking was red > white = yellow ≥ blue =green. The ranking on the hydrogen production performance was white > yellow > green > blue > red without stirring and white > yellow ≥ blue ≥ red >green by stirring.（3） The optimum growth temperature and hydrogen production temperature were all 35.0 °C. The maximal hydrogen production rate and cumulative hydrogen production reached 78.7 ml/L/h and 1728.1 ml H2/L culture, respectively, under 35.0 °C and 240 rpm.（4） Ca²⁺ and Fe²⁺ promoted the bioflocculation of PB-Z and greatly promoted the hydrogen production in the case without stirring.（5） When pyruvate was used to replace glucose as the carbon source, the component of H2 and CO₂ changed from 55% and 45% to 95.9% and 4.1% respectively. In addition, there was a good linear relationship between the hydrogen content and intracellular pyruvate concentration. This indicated that pyruvate was one of the main sources of CO₂ and has a great impact on the gas composition.（6） If the content of NH₄⁺-N was very low during the hydrogen production, a small amount of carbamide was converted to NH₄⁺-N, which was used as the nitrogen source for growth.（7） The maximal hydrogen production rate and cumulative hydrogen production were all decreased a little by the new photobioreactor. This may be because the insufficient stirring and increasing height of the new photobioreactor go against the hydrogen bubbles removing from the culture medium.（8） PB-Z could not utilize the low-molecular-weight organic acids for hydrogen production if the media did not contain vitamin. And PB-Z could utilize carbamide and ammonium chloride as nitrogen sources for growth and hydrogen production but could not use glutamic acid. However, the nitrogenase activity was decreased and strongly inhibited by ammonia.（9） When total N content was 0.02 mol/L, PB-Z had high activity of hydrogen production at C/N=3.5 and losed its activity at C/N=10.5. Nevertheless, PB-Z had high activity of hydrogen production at C/N=10, when total N content was 0.003 mol/L. This showed that carbon source、nitrogen source and C/N influenced on each other. Furthermore, PB-Z was suitable for continuous hydrogen production. In conclusion, PB-Z has excellent performance in hydrogen production.