Effect Of Spectrum On Hydrogen Production By Photosynthetic Bacteria

This paper consists of a series research supported by the National Natural Science Foundation (No. 50676029) and national"863"plan (No.2006AA05Z119).Nowadays , with the rapid development, energy shortage has become the key restrictive factor of the development., For fossil energy is non-renewable and causes serious pollutions, research and application of clean and renewable energy has been put on the agenda in each country. Photosynthetic bacteria (shorted as PSB )can use the extensive sunlight for photosynthesis, transform the sunlight into their own energy for metabolism, meanwhile the hydrogen was produced, and PSB can decompose various of organic matters which can be used as waste treatment. For non-consumption of mineral resources, using PSB for hydrogen production has been paid attention by most of the countries.For light resources of PSB were selectable, taking the mixed photosynthetic bacteria cultured by our team as the research object and different monochromatic light including incandescent lamp in the lab as light sources, hydrogen production law was studied, contrast tests were carried out using the Uniform design method, then the test results were analyzed and optimized using the Uniform Design software.The main research contents and results are as following:1.From the result of spectroscopic assay in 300nm⁹00nm, it is found that the mixed photosynthetic bacteria has a obvious absorption peak in 390nm,490nm,590nm and 800nm,860nm which belong to infrared light district. The mixed photosynthetic bacteria has the same absorption peak as the single strain indicating that when the single strains were cultivated together, they still keep the character as before. By analyzing the absorption peak, it is known that mixed photosynthetic bacteria contained carotenoids such as bacter-iochlorophyll a, photosynthetic pigments.2.The growth curve of Photosynthetic bacteria consistent with each other under different light , the lag phase, logarithmic phase, stationary phase, decline phase are obvious. The four corresponding phases are 0³6h, 36⁷2h,72h⁹6h and the time after 96h.Based on the impact of different light on the growth of PSB, the order is as follows: yellow light> blue> green> Incandescent> white> red.3.The results of single-factor experiment such as temperature, light intensity, initial pH value, PSB early activity and NH4+concentration:When the temperature was below 32℃, the velocity and volume of Hydrogen production increased with the temperature raised; when the temperature raised to a certain degree, the activity of PSB was inhibited: when the temperature was above 32℃, the velocity and volume of Hydrogen production by PSB with LED began to decline. Because of heat dissipation of Incandescent lamps, the environmental temperature was dynamic, as a result the environmental temperature raised, which inhibited the activity of PSB in some extent.Light intensity was also a important factor on hydrogen production, when the Light intensity was below 1600lux, the velocity and volume of Hydrogen production increased with Light intensity raised. when the Light intensity was above 2000lux, the velocity and volume of Hydrogen production began to decline, which may due to the"light saturation effect".The initial stage of hydrogen production, too acidic or alkaline condition went against the release of hydrogen. When the initial pH value was 4, hydrogen production of photosynthetic bacteria with different light were inhibited with excessive cell death and very low production velocity, the maximum production rate was 9.6mL/L?h; When the pH was 8,the initial stage of hydrogen-production was inhibited, while hydrogen production rate in the 72h steadily improved owing to the acid metabolism and, and the cycle of hydrogen production was longer. The suitable pH volume in early stage of hydrogen-production was 6～7.Different PSB with different initial activity had little impact on the volume and velocity of the hydrogen production under different light resources. From the general amount, the hydrogen production of PSB with initial activity as 48h 60h was the largest. The decreasing order of hydrogen production was PSB with yellow, green, blue, incandescent, white light and red light.The inhibitory effect of NH4+ concentration on different PSB was different. The suitable NH₄⁺ concentrations for PSB with yellow and blue light were 0.2g/L and 0.4g/L,while for PSB with green light, it were 0.4g/L and 0.6g/L.The hydrogen production of PSB with write and red light were lower than others, for which the most suitable NH₄⁺ concentration was 0.2g/L, the suitable NH₄⁺ concentration of PSB with Incandescent was 0.4g/L.By experiments and analysis of Uniform Design software, the best combination was yellow light with 1600lux at 32℃.