Screening Of Mixed Photosynthetic Culture And Researches Of Its Hydrogen Prodution

Being an ideal energy carrier,hydrogen has many advantages,such as non polluting nature,combustion releases high heat,easy to reserve and output,widespread sources and so on.Among the methords for biological hydrogen production technology,the photofermentation process by photosynthetic bacteria has attracted intensive attention,mainly due to low energy consumption,high H₂ production efficiency,high substrate degradation rate,and the coupling of wastewater treatment and energy production.In this paper,the photosynthetic hydrogen-production bacteria were enriched from lake bottom silt by using the culture medium,and named NG07.It was identified by the universal 16 S rDNA gene primers for high-throughput sequencing.According to our analysis,Rhodopseudomonas oryzae and Rhodobacter sphaeroides were predominant microorganisms present in a microbial consortium NG07.The effects of substrate and environmental factors on the growth and hydrogen production characteristics of mixed culture NG07 were analyzed in this study.The experimental results showthat:?1?mixed culture NG07 have the ability to use many carbohydrate organic compounds for hydrogen production.The highest cumulative hydrogen yield can be obtained when the glucose was carbon source.The cumulative H₂ yield increased observably with the glucose concentration increased from 10 to 130 mM.The maximum cumulative H₂ yield?4238.8 ± 74 mL/L?was obtained under the concentration of 100 mM.But the glucose concentration had different influences on the hydrogen production rate,the substrate conversion rate and the glucose degradation rate of mixed culture NG07.The maximum hydrogen production rate?105.28 ± 7.6 mL/h/L?,the maximum substrate conversion rate?15.37%?and the maximum glucose degradation rate?99.40%?were found to be at the glucose concentration of 70 mM.?2?The maximum cumulative H₂ yield of 2872.2 ± 38.31 mL/L and the maximum hydrogen production rate of 105.28 ± 7.6 mL/h/L were obtained under the urea concentration of 20 mM.?3?The optimal Fe²⁺ concentration was 5 mg/L.When the concentration of Fe²⁺ was 5 mg/L,the maximum cumulative H₂ yield and the highest hydrogen production rate of 3102.5 ± 95.7 mL/L,114.9 ± 9.1 mL/h/L,respectively.And which they increased by 1.94 times and 2.54 times compared with the control test,respectively.?4?Stirring can improve the hydrogen production rate of photosynthetic bacteria,and shorten the reaction residence time.But under the stirring condition its cumulative H₂ yield did not sharply increase.The hydrogen production rate was 136.0 ± 5.6 mL/L/h when stirring,and it increased by 29% compared with the control test?105.28 ± 8.1 mL/h/L?.?5?35 ? was found the optimum temperature for hydrogen production by mixed culture NG07.But under the temperature of 40 ?,NG07 still has good performance of hydrogen production performance,the cumulative H₂ yield of 2638.5 ± 52.7 mL/L was achieved.NG07 still had hydrogen production activity,the cumulative H₂ yield was 1050.0 ± 28.7 mL/L at 45 ?.The result shown that NG07 had a better ability to adapt to temperature changes.?6?Light conditions shown different impact in the cumulative H₂ yield and the hydrogen production rate.The ranking on the cumulative H₂ yield was 12 h dark/12 h light cycle condition > continuous illumination condition ? continuous dark condition > 12 h light/12 h dark cycle condition.The ranking on hydrogen production rate was 12 h dark/12 h light cycle > continuous light > continuous dark ? 12 h light/12 h dark cycle condition.?7?When the polyvinyl alcohol was used as the carrier to immobilize cells,the hydrogen production activity of the mixed culture NG07 was obviously higher than other materials?agar and sodium alginate?.?8?Based on single-factor experiments,Box-Behnken Design was carried out to optimize the hydrogen production process in which the maximum hydrogen production rate as evaluation index.RSM results revealed that the highest hydrogen production rate of 199.3 ± 6.5 mL/L/h can be obtained when Fe²⁺ concentration,temperature and the glucose concentration were 4.39 mg/L,33.36 ?,78.32 mM,respectively.And it increased by 29% compared with the center condition.It can be seen that the optimal conditions obtained by the multi-factor experiment are different from the best conditions obtained by the single-factor experiment,which reveal the interaction between each independent variable.