Excavation And Regulayion Of Key Proteins Of Extracellular Polysaccharide Production By Sclerotium Rolfsii

Scleroglucan is an extracellular polysaccharide produced by some species of the genus Microcaries.It is widely used in petroleum,chemical and food fields due to its good thickening and moisturizing properties.In this study,several key proteins affecting the yield of polysaccharides were identified by laboratory strains Sclerotium Rolfsi I(SMR-1046),which provided theoretical basis for improving the properties of extracellular polysaccharides by regulating the levels of key genes involved in the synthesis of polysaccharides.At the same time,the fermentation process was optimized to improve the utilization rate of raw materials,reduce waste and environmental pollution caused by industrial production,and provide reference for the industrial application of polysaccharides.In the early stage,three types of exopolysaccharides were screened according to the yield and year of polysaccharides,namely,the exopolysaccharides obtained by fermentation with glucose,sucrose and lactose as carbon sources,respectively,and were named SEPS(high yield and high viscosity),GEPS(medium yield and medium viscosity)and LEPS(low yield and low viscosity).Metabolome sequencing and transcriptome sequencing were performed on the bacteria fermented with three carbon sources.The number and expression levels of genes with significant differences under different carbon sources were analyzed and annotated,and their GO term and KEGG pathway were enriched and analyzed.Combined analysis of transcription and metabolism revealed that the metabolites and genes in the three comparison groups were mainly related to the function of "genetic information process","metabolic process" and "environmental information",and mainly involved in alanine,aspartic acid and glutamic acid metabolism,purine metabolism and biosynthesis of aminoyltr NA.Through joint analysis on extracellular polysaccharide synthesis route and key proteins,rt-pcr results show that several gene expression level is consistent with the transcription omics data,enhancer and inhibitors added once again proved that phosphate glucose mutase,glutamate synthetase,6-fructose phosphate enzyme is the key to the polysaccharide synthesis protein kinase 1 and so on.It was determined that adding glutamic acid at 0 h of fermentation and lysine and fructose 6-phosphate disodium at 24 h of fermentation could significantly increase the yield of extracellular polysaccharide.Response surface analysis(RSM)was carried out to optimize the control process of polysaccharide synthesis and fermentation with polysaccharide yield as the response value.The final dosage was determined as fructose 6-phosphate disodium 0.7 g/L,lysine 0.24 g/L,glutamate 1 g/L.According to the data of fermentation process,it was found that the addition of the fortifier improved the utilization rate of glucose by the integrated micronucleus,and finally made the maximum yield of polysaccharides of micronucleus reach 16.12 g/L.