Mechanism Of Bio-adsorption And Bio-transformation Of Chromium By GTF High Yield Strain YSI-3.7

GTF as a product of yeast enriched Cr(III),has the functions of enhancing insulin function,promoting glucose metabolism and lipid metabolism,reversing glucose intolerance,increasing glucose tolerance,protecting insulin beta cells,increasing the number and affinity of insulin receptors.Because of its high yield and high safety,yeast chromium has attracted much attention from scientists both at home and abroad.However,the mechanism of yeast enrichment of Cr(III)has not been elucidated.Therefore,the laboratory strain YSI-3.7 was selected and the high yield GTF strain was induced by layer induction.We have done the research from the following aspects,such as the distribution of chromium in yeast,the effects of yeast groups on chromium content,the differences in gene expression between yeast and chromium in the process of redox changes,et al.To a certain extent,the mechanism of yeast enrichment of Cr(III)to form GTF is clarified to provide a theoretical basis for the industrial production of GTF.We get the following conclusion:1.When the concentration of Cr3+ was 500 ?g/m L,the total chromium and organic chromium content of YSI-3.7 were the highest,reaching 1803.87 ?g /g.dcw and 1133.91 ?g/ g.dcw respectively.Chromium in the cell wall was basically inorganic chromium,accounting for 14.43% of total chromium accumulation,and chromium on Protoplasts accounted for 85.57% of total chromium,73.29% of which was mainly organic chromium.The chromium content was evenly distributed in the yeast cells regardless of the cross section of the bacteria and the analysis of the depth of the chromium.2.The chemical shielding of the yeast surface groups,yeast surface amino,carboxyl and phosphate groups have great influence on the amount of chromium rich yeast.However,ester and carboxyl have little effect.The results of FTIR analysis also confirmed the above results.3.RNA-Seq sequencing results showed that there were 2333 differentially expressed genes identified between the blank group of YSI-3.7and chromium enriched yeast(500 ?g/m L Cr3+).Among them,1273 genes were up-regulated and 1060 genes were downregulated.According to the annotation of KEGG database,98 metabolic pathways were changed,which had the greatest influence on ribosome metabolism,sulfur metabolism,oxidative stress metabolism,carbon metabolism,cysteine and methionine metabolism.According to the annotation of GO database,they are classified into three categories: biological pathways(778 pathways),cell components(173 pathways),and molecular functions(594 ways).Among them,GSH2,SPE4,MET16,CYC1,MSN4 are the most significant differences.4.The content of MDA in yeast cells increased with the increase of Cr3+ concentration,and the degree of membrane lipid peroxidation.Under the action of low concentration(0~500 ?g/m L)Cr3+,YSI-3.7 could prevent Cr3+ oxidative stress by increasing total antioxidant capacity(T-AOC),glutathione(GSH),thiol content and glutathione oxidase(GSH-Px)activity.The changes of superoxide dismutase(SOD)and peroxidase(CAT)activity were not obvious in this process.1m M Na2SO3 can improve the amount of chromium enrichment,and increased GSH,T-AOC,-SH in YSI-3.7.