Study On Growth Characteristics And Microbial Protein Synthesis Of Photosynthetic Bacteria Affected By C/N Ratios

The traditional wastewater treatment technology mainly aims at pollutant removal,which needs to consume a lot of energy.Under the guidance of the concept of sustainable development and the concept of green-ecological environment protection,the use of microorganisms to simultaneously achieve pollutant removal and resource recovery to produce microbial protein,has become a promising sewage treatment technology.Microbial protein has unique advantages of high production efficiency,high labor productivity,high content of nutrients and extensive sources of raw materials.These advantages make microbial protein a new development direction in the field of sewage resource recovery.Photosynthetic bacteria(PSB)can effectively assimilate the organic matters and nitrogen elements in the wastewater to synthesize its microbial cells,and achieve rapid growth and reproduction.Photosynthetic bacteria cells are rich in protein,which makes it a suitable target microorganism for microbial protein production.However,the relevant research is still in its infancy.In the current researches,the factors that affect the growth of photosynthetic bacteria,especially the proportion of microbial protein in PSB,are still unclear.There are significant differences in the carbon nitrogen ratio of different kinds of wastewater.However,the study about the effects of carbon nitrogen ratio on the quality of microbial protein and the population structure of photosynthetic bacteria has not been reported.So in this study,photosynthetic bacterias are taken as the research object,and the goal is to realize the recovery of sewage resources.Different carbon nitrogen ratio conditions were set to explore the effect of carbon nitrogen ratio on the growth characteristics of photosynthetic bacteria and the synthesis of microbial protein.The main results are as follows:(1)It was found that the C/N ratio had a significant effect on biomass accumulation,pollutants degradation and microbial protein synthesis in the two cycles of shaking flask culture.Generally speaking,under the condition of high C/N ratio,microbial growth,ammonia nitrogen and COD removal rates were higher,while the ratio of microbial protein in PSB was the highest under the condition of C/N ratio was 1,reaching 56.48%and 62.46%in two cycles respectively.The removal of NH4+/COD(g/g)in the group of C/N=1 was also the highest,which was 0.41 and 0.39 in the two cycles respectively.The results showed that the microbial protein in PSB synthesized by ammonia nitrogen and nutrient assimilation in sewage was higher under the condition of low C/N ratio.(2)Through the high-throughput sequencing analysis of the microbial samples in the shaking flask systems,it was found that the microbial community has a strong functional specificity,and the genus Exothiorhodospira is the main functional bacteria in the system,occupying an absolute predominance under each C/N ratios.In addition,under the condition of high C/N ratios,there is also a high proportion of Proteiniclasticum with the main function of decomposing protein,as well as Alkalophilus and Halomonas with the function of organic matter decomposing,which can explain why when the C/N ratio increases,although the degradation rates of ammonia nitrogen and COD increase,the proportion of microbial protein in PSB decreased.(3)The feasibility of producing microbial protein from three kinds of wastewater was analyzed.The process flow,and sequencing batch reactor for wastewater resource recovery based on the growth of photosynthetic bacteria were designed.The process flow includes four stages:pretreatment stage,sequencing batch reactor of photosynthetic bacteria,recovery of photosynthetic bacteria cells and advanced treatment.In the pretreatment stage,it is necessary to adjust the pH,flocculate and precipitate macromolecular nutrients and add an anaerobic digestion links,so as to provide favorable growth conditions for photosynthetic bacterias,such as available small molecular organics and so on.The reactor shall be designed as a flat cuboid according to the characteristics of photosynthetic bacteria,adding magnetic agitation device,heating and temperature controling device,aeration device,etc..The process flow utilizes membrane separation technology to recover photosynthetic bacterias which has high operability and recovery efficiency.There are 31 pictures,22 tables and 108 references.