Hydrogen photoproduction from acetate by Rhodopseudomonas palustris / 生物工程学报

Based on the characteristics of metabolism of photosynthetic bacteria and the major kinds of organic compounds produced in wastewater degradation, eleven kinds of organic compounds were chosen for hydrogen photoproduction using Rhodopseudomonas palustris Z strain. The maximal volumetric H2 productivity was obtained using acetate as the sole carbon source and electron donor. The kinetics of cell growth and H2 liberation, and the influences of several major limiting factors on photoevolution of H2 were examined using acetate as carbon source. It was shown that hydrogen production was partially correlated with cell growth. The medium composition of the preculture, the preculture time, and inoculation volume were confirmed to have big effects on hydrogen photoevolution. The time delay of H2 production was evidently shortened using the inoculum of late exponential growth phase or stationary phase using ammonium sulfate as nitrogen source or with the inoculum of middle exponential growth phase using glutamate as the nitrogen source. The identity of temperature and light intensity for H2 evolution and cell growth has significant potential application in the technology of splitting organic acid into H2 by photosynthetic bacteria. The concentrations of acetate and glutamate in the medium affected hydrogen photoevolution and cell growth significantly. The productivity of H2 increased with substrate concentrations when substrate concentrations of sodium acetate and sodium glutamate were lower than 70 mmol/L and 15 mmol/L, respectively. Hydrogen production was inhibited but the cell growth was faster when the concentration of sodium glutamate over 15 mmol/L due to forming free NH4+. The highest rate of hydrogen production was 19.4 mL.L-1.h-1 using 30 mmol/L of sodium acetate as hydrogen donor under the standard conditions, respectively. The optimal conditions for hydrogen production were 35-37 degrees C, 6000-8000 lx and pH 7.3-8.3. The effects of oxygen and inoculation volume on photoproduction of hydrogen were also discussed.

The Mutagenesis and Screening of Carotenoid Mutant in Hydrogen-producing Photosynthetic Bacteria / 微生物学通报

Mutagenesis and screening of hydrogen-producing photosynthetic bacteria,Rhodobacter sp.R7 strain,was investigated by using the combination mutation of ultraviolet ray and LiCl and layer plating methods.A carotenoid mutant named R726 strain was obtained.The plate phenotype properties in carotenoid mutant were different from that of parent strains.Living cells spectra showed that absorption peak of 550 nm was appeared in carotenoid mutant,but not in parent strain.The absorption spectra of extraction of pigment further confirmed the difference of carotenoid composition between the mutant and parent strains.The result of TLC on silica gel plate showed that mutant has a lack of yellow carotenoid composition which occurs in parent strain.H_2 productivity and biomass in carotenoid mutant was higher than that of parent strain.These results revealed that mutant has a modified carotenoid biosynthesis pathway.

Extraction and Separation of Carotenoids of Hydrogen-Producing Rhodobacter sp / 微生物学通报

Carotenoids play an important role in regulating the hydrogen production of hydrogen-producing Rhodobacter sp. The carotenoids of hydrogen-producing Rhodobacter sp. grown in acetate medium were extracted by using acetone-methanol (7∶2,V/V) solvent and were separated by using thin-layer chromatography on silica-gel plate. The qualitative and quantitative of the carotenoids were analyzed by spectrometry. The results showed that the carotenoids were completely extracted three times with acetone-methanol (7∶2,V/V) in two hours. The ultrasonication had little effect on yield of carotenoids. The yield of carotenoids was 2.81mg/g wet cell. There were 4 spots on the silica-gel plate in the order of yellow, red, light red and light yellow. Yellow spot and red spot were the dominant composition of carotenoid in Rhodobacter sp. The spectrometry data showed that the yellow and red component might be the spheroidene and spirilloanthin respectively.