The Application Of LED Light Source In Photosynthetic Bacteria Cultivation

Photosynthetic bacteria have been widely used in the research fields of the wastewater treatment,biological hydrogen production,producing single cell protein and so on,because of their special and useful physiological characteristics.Traditional light source of the photosynthetic bacteria cultivation was the incandescent bulb.But it had several disadvantages,such as the short life,high cost and large electricity consumption.Besides,this traditional industry will be shut down soon.LED lamp with the great efficiency and energy saving is one of the best alternative light sources.In this research,we isolated two kinds of photosynthetic bacteria,Rhodopseudomonas palustris and Rhodospirillum rubrum.We studied the influence of LED lamps with different conditions on the growth of the two bacetria.In addition,we tried to optimize the growth medium,and use the quantitative PCR method to explore the effects of different LED lights on the mixed bacteria growth.Finally,we researched the utilizing,recycling and transforming the food wastewater into resources by photosynthetic bacteria preliminarily.The results showed that:(1)The optimal growth conditions of Rhodopseudomonas palustris were "LED light:blue,light intensity:5000 lux,initial pH value:7?8,inoculate quantity:10?12%".While the optimal growth conditions of Rhodospirillum rubrum were "LED light:yellow,light intensity:5000 lux,initial pH value:7?8,inoculate quantity:10?12%".The growths of two bacteria with LED light were better than the growths with incandescent bulb,and the cost of cultivaton wit LED light is less too.(2)Through the response surface experiment,we modified the meuim.The formula were "sodium acetate(2g/L),sodium glutamate(0.1 g/L),ammonium chloride(1g/L),magnesium sulfate(0.4g/L),KPD(0.5g/L),sodium chloride(1g/L),yeast extract powder(1g/L)."(3)In the mixed growth medium of the Rhodopseudomonas palustris and Rhodospirillum rubrum,the longest logarithmic phase and the largest amount of bacteria were reached when using the blue LED light;the shortest lag phase and the fastest early growth rate were reached when using the yellow LED light;qRT-PCR could be used to estimate the percentages of such two kinds of bacteria.Furthermore,the predominant bacteria were Rhodopseudomonas palustris with the blue LED light,yellow LED light or mixed blue-yellow LED light.And two bacteria would almost grow similarly with the white LED light.(4)Photosynthetic bacteria could use the food wastewater as their nutrients.When using LED light as the light source rather than the incandescent bulb,the photosynthetic bacteria always grew better and the removal rate of COD was higher,too.The highest removal rate of COD in the supernatant could be about 75%.