Study On The Effect Mechanism Of Mixotrophic On The Lipid Accumulation Of Desmodesmus

The problem of water pollution and the shortage of water resources are becoming increasingly severe,and nitrogen and phosphorus in sewage cannot be effectively used as a precious resource.Because microalgae are resistant to many sewage and have a high accumulation potential for lipid production Therefore,coupling wastewater treatment and microalgae cultivation can effectively reduce the cost of microalgae cultivation and sewage treatment.The effects of different sewage treatment methods on nitrogen and phosphorus removal and lipid accumulation were studied,and discussed the influence of bacterial flora in the sewage on the lipid accumulation of microalgae,the lipid accumulation of microalgae in sewage differences in metabolic pathways of mass accumulation.The effects of Desmodesmus sp.growth on nitrogen and phosphorus removal,triglyceride accumulation and photosynthesis in sewage were studied.The results of the study showed that the growth rate and pigment content of Desmodesmus sp.were higher under autotrophic conditions,and the mixed culture conditions were beneficial to the removal of nitrogen and phosphorus in sewage and the accumulation of lipids in algae cells.Especially in the domestic sewage II,the triglyceride concentration in the algae cells increased by 107.65 mg/L compared with the autotrophic condition,the total lipid content also increased by 19.46%,and the carbohydrate content reached 45.05%under the autotrophic condition.Using high-throughput sequencing to measure bacterial diversity in unsterilized wastewater showed that the YG-2 community has a high species richness and diversity,which inhibits changes in its external environment.Bacteria in which the door is mainly horizontal Proteobacteria and Bacteroides based,which contribute to the degradation of pollutants.More sewage lipid accumulation microflora species composition in relative abundance superpathway of fatty acid biosynthesis initiation,fatty acid elongation-saturated,mycolate biosynthesis(the second fatty acid biosynthesis pathway)are large,description thereof bacterial synthesis of fatty acids It has a certain role in promoting.Transcriptome sequencing was used to compare the metabolic pathways of autotrophic and mixotrophic to reveal the lipid accumulation of Desmodesmus sp.in mixotrophic.The results showed that the mixotrophic group had 1081 up-regulated genes,575 down-regulated genes,and 23331 non-significantly differentially expressed genes.According to the enrichment results of the differential gene,the enrichment of the differential gene GO is mainly in the molecular functions,biological processes and cell components of photosynthesis,such as thylakoid,photosystem I,chlorophyll binding,photosynthetic electron transport,light response and dark Response etc.The most significant metabolic pathway enriched by KEGG pathway is photosynthesis,followed by fatty acid elongation,protein processing in the endoplasmic reticulum,and starch and sucrose synthesis.The difference in gene expression in photosynthesis shows that mixotrophic reduces PS Ⅱ ’s demand for light energy,but under mixotrophic conditions,photosynthetic electron transport is enhanced,producing more ATP and NADPH for carbon fixation in photosynthesis and other metabolic activities of cells.The enhancement of lipid accumulation is mainly due to the enhancement of glycolysis pathway,which produces more acetyl-Co A for fatty acid production and promotes fatty acid production.