Study On Photofermentative Hydrogen Production And Mutagenesis Of Rhodobacter Azotoformans Y6

Hydrogen production (2H++2e-?H2) from organic sewage by photosynthetic bacteria (PSB), a group of archaebacteria, can be classified into photofermentative hydrogen production and dark fermentative hydrogen production. The dark fermentative hydrogen production is mainly catalyzed by hydrogenase. The photofermentative hydrogen production is catalyzed by nitrogenase which associated with photosynthesis and carbon metabolism. In this process, proton and electron required for hydrogen production were mainly provided by carbon metabolism, while ATPs were generated by photosynthetic system.The PSB strain Y6 was identified as Rhodobacter azotoformans by analysis of morphology, physiology and 16S rDNA sequences. The fermentative hydrogen production by PSB was studied using propionate as sole carbon source. After single-factor and orthogonal experiment, the optimal conditions for hydrogen production were achieved as: temperature 30℃, initial pH value 7.0, bacteria inoculation proportion 20%, propionate concentration 20 mmol/L and light intensity 3000lux. Under the optimized conditions, the maximal hydrogen production and the maximal rate were 0.033 mol/Lcult (corresponds to 0.74 L/Lcult) and 7.2×10-4 mol/(Lcult·h) (corresponds to 0.016 L/(Lcult·h)), respectively, with a hydrogen conversion efficiency of 55%.The pigment mutant and auxotrophic mutant strains were obtained using ethyl methane sulfonate (EMS) and LiCl as mutagenic reagents. The optimal conditions for obtaining pigment mutant were: 1% EMS, 0.3% LiCl, treating for 30 min. To get auxotrophic mutant, the optimum conditions were: 1% EMS, 0.5% LiCl, treating for 30 min. Spectrum analysis of carotenoid pigment from mutant YM5-3 showed a 10 nm (on average) blue shift of absorption peak. The HPLC and mass spectrum analysis suggested a dramatically accumulation of neurosporene, which might be caused by the block of the biosynthesis of hydroxyneurosporene and the subsequent pathway. The maximal hydrogen production by YM5-3 was increased 9% while the...