Screening And Immobilization Of High-efficiency Sulfate-reducing Flora And Its Application In Desulfurization Of Corn Steep Liquor

Corn steep liquor（Corn steep liquor,CSL）is a by-product of corn starch production,China’s annual output is about 30 million tons,its nutrients are rich（such as polysaccharides,proteins,vitamins,amino acids and trace elements,etc.）,currently mainly used as feed raw materials.Because corn steep liquor contains harmful ingredients such as sulfites,it seriously inhibits the development of its application value and causes a huge waste of resources.In this paper,we tried to screen out the high-efficiency sulfate-reducing bacteria（population）and used immobilization technology for the biological desulfurization of corn soaking solution,and the main results are as follows:（1）Postgate C medium（sulfate-reducing bacteria exclusive medium）was used to enrich a highly efficient desulfurization flora with a desulfurization rate of 83.25%and adapted to a variety of different sulfur sources.The results of high-throughput sequencing showed that the dominant bacteria in the flora were Citrobacter,Enterobacter and Clostridium＿sensu＿stricto＿13,and their abundance was about 25.9%,18.3%and 15.8%,respectively.Compared with the sulfate-reducing bacteria monoplicity screened out in the flora,the desulfurization effect of the flora was significantly better than that of the monobacteria,indicating that there was a synergistic effect between the flora,or the efficient desulfurization strains in the flora were not easy to screen and culture.（2）The results showed that the optimal desulfurization temperature of sulfate-reducing flora was 35℃,the optimal desulfurization p H was 7,the optimal inoculation amount was 5%,and the desulfurization effect was best when the initial concentration of SO₄^2-was 0.5 g/L,and the removal rate of SO₄^2-could reach 94.74%.（3）The univariate optimization test on the immobilization conditions of microflora showed that the PVA concentration was 8%,the SA concentration was 0.5%,the Ca Cl₂concentration was 2%,the crosslinking time was 8 h,and the bactericogel ratio was 1.5.The results of multi-factor orthogonal test showed that PVA concentration had the most significant effect on the desulfurization ability of immobilized sulfate-reducing flora,and the optimal immobilization conditions for sulfate-reducing flora were PVA concentration of 8%,SA concentration of 0.5%,Ca Cl₂concentration of 2%,immobilization time of 8 h,and mycogel ratio of 2.0.Immobilized spheres prepared under this condition can remove91.3%SO₄^2-for 3 days.（4）Add 2.0g sulfate reducing flora immobilization ball to corn steep liquor diluted5 times per 100ml,and after 48h of desulfurization,the sulfite content of corn steep liquer can be reduced from 86.7 mg/100m L to 11.3 mg/100m L.After the immobilized ball was recycled 8 times,the appearance of the immobilized ball did not change significantly,and more than 55.51%of sulfite in corn steep liquor could still be removed.The use of desulfurized corn steep liquer and bacterial solution to gavage SD rats did not adversely affect the percentage change of body weight,feed weight ratio,spleen index,liver index and colon index of SD rats.In this paper,the biological desulfurization of corn steep liquor was carried out for the first time,and the screened sulfate reducing flora had high desulfurization activity,which could be used for a variety of sulfur sources,and the immobilized flora had good desulfurization effect on corn steep liquor,and it was not toxic,and had great application prospects in the treatment of corn steep liquor and other sulfur-containing wastewater.