Simultaneous Enrichment Of Selenium And Zinc By Pleurotus Ostreatus In A Liquid Fermentation Process

This study investigated the simultaneous enrichment of the two element selenium and zinc in liquid fermentation process of P.ostreatus,explored the interaction between the two element during enrichment and its influence on mushroom nutrients.This research provided a reference for the development of high value-added dietary supplements.The main conclusions of this paper are as follows:(1)High concentration of Se and Zn can seriously inhibit the growth of P.ostreatus mycelia,so it is particularly important to select the appropriate Se and Zn addition concentration.Their effects on mycelium biomass,the total amount of selenium and zinc content,and the selenium and zinc enrichment efficiency were determined.The optimal Na₂SeO₃ addition concentration was 1ppm,ZnSO₄addition concentration was 400 ppm,then the total amount of selenium and zinc was 0.20 mg·L^-1 and 31.01 mg·L^-1,respectively.The intercellular polysaccharide(IPS)and extracellular polysaccharide(EPS)with 1 ppm Na₂SeO₃were 0.12 mg·m L^-1 and 35.18 mg·g^-1,respectively.The values with 400 ppm ZnSO₄were0.12 mg·m L^-1 and 28.12 mg·g^-1,respectively.(2)Taking the total amount of selenium and zinc as the index,Na₂SeO₃ and ZnSO₄ were added separately at 1ppm and 400 ppm,respectively.The fermentation time,Na₂SeO₃ and ZnSO₄ addition time,inoculation amount and p H were optimized,and the effects on polysaccharide content were also studied.Results showed that the optimized fermentation time and inoculation amount were 7 d and 0.6 g,the adding time of Na₂SeO₃was 1d,the ZnSO₄adding time was 0 d,and the p H values for Se and Zn were 8.5 and 6.5,respectively.After optimization,the enrichment of Se and Zn were 0.27 mg·L^-1 and 50.23 mg·L^-1,respectively,increased by 35.00%and 61.98%.EPS and IPS were increased by 116.67%and93.12%treated with Na₂SeO₃.EPS and IPS values increased by 50.00%and 165.54%treated with ZnSO₄.(3)In order to simultaneously enrichment Se and Zn by P.ostreatus,the mixed addition process of Na₂SeO₃ and ZnSO₄ was further explored,and the total Se and Zn content reached76.65 mg·L^-1 with the fermentation condition that fermentation time and inoculation amount were 7 d and 0.6 g,the adding time of Na₂SeO₃ was 1d,the ZnSO₄ adding time was 0 d,and p H 6.5,increased by 51.68%.In addition,the increase of Zn concentration could promote the enrichment of Se at low Se concentration,the enrichment of Se was inhibited with the increase of Zn concentration at high Se concentration.while Se had no effect on the enrichment of Zn at the same Zn concentration.(4)In P.ostreatus,Se was mainly binding to protein,while Zn mainly binding to polysaccharide.These two elements addition had no effects on the amino acid composition and monosaccharide composition of mycelium,but they could change the molecular weight and proportion of polysaccharide.The molecular weight and proportion of macromolecules polysaccharides decreased,while the proportion of low-molecular polysaccharides increased.The main selenium species formed in the mycelium of P.ostreatus was in organic forms,further proving that P.ostreatus mycelium could convert inorganic selenium into organic selenium,and have the potential functioning as dietary supplement.These results provide ideas and methods for the development of dietary supplements rich in selenium and zinc.