Screening And Enhancement Of Selenium-enriched Yeast

Selenium(Se)is an essential trace element for humans,and Se deficiency is linked to several chronic diseases such as cancer and heart disorders.In order to reduce the risk of these diseases,Se supplementation in the diet is a good option in most circumstances,so that Se-enriched yeast has an important application in medical care and pharmaceutical industry due to its high bioavailability and safety in food additives.Se-enriched yeast is difficult to carry out large-scale and efficient industrial production of selenium enriched yeast,which restricts the wide application of selenium enriched yeast due to yeast of unstable ability rich-selenium,selenium accumulative and growth discomfort in the study of selenium enriched yeast.In order to improve the ability of yeast to enrich selenium,the paper studies the selection of selenium rich soil in Xinjiang as the sample source,screening the natural selenium enriched yeast strains with better selenium enrichment ability and tolerable tolerance as the research object,the optimal technological conditions for selenium and growth of yeast.The aim is to achieve high efficiency accumulation and cell growth of selenium in yeast strain.The results are as follows.Fifity samples of selenium rich soils were collected from the northern slope of Tianshan Mountain of Sha Wan,Xinjiang.A yeast strain with relatively high selenium content and relatively high biomass were obtained by screening the initial of the Martin culture medium and rescreening the ability to enrich the selenium,which had the initial selenium amount of 790.0 ?g/g and biomass of 4.64 g/L.By 18 S rDNA sequence analysis and strain morphological identification,the strain was determined to be Rhodotorula glutinis which was designated as X-20.It was preserved in the China Center for Type Culture Collection(CCTCC)with a preservation number CCTCCM2017225.The culture conditions and medium of Rhodotorula glutinis X-20 were optimized to accumulation of selenium,the optimal conditions were obtained as temperature 30 ?,initial pH = 7,inoculation volume 1%,volume-loading 50 mL/250 mL,culture time 60 h,the selenium content of yeast will be importantly improved by using 2% glycerol as carbon source.Supplying concentration 50 mg/L of sodium selenite at 12 h of cultivation can keep the higher selenium content and biomass.Addition of 0.4 mM phosphate can efficiently increase the transport and accumulation of selenium,and make the selenium content and biomass of strain R.glutinis X-20 achieved 3949 ?g/g and 4.23 g/L,respectively.And the Se-enriched yeast production increased by 17.2% compared to that of pre-feed by utilizing glycerol feed fermentation.A balanced culture method for yeast growth and selenium enrichment was studied,and the yield of selenium rich is increased effectively via transfering heterologous phosphate transporter Pho84 into Rhodotorula glutinis X-20 for regulating the transport of selenium in yeast cells,which enhanced the efficiency of selenium the selenium-enriched amount of yeast reached 5000 ?g/g,and the biomass increased by 11.2%.By using a culture method of simple mixed carbon source(the ratio of glycerol and glucose is 3:7),the biomass and selenium-enriched content reached 5.3 g/L and 5349.6 ?g/g,respectively,achieving the balance of cell growth and selenium accumulation.