Research On Key Technologies Of Microbial Post-treatment For Biomass Enrichment By Nuclides

The exploitation and utilization of nuclear energy have brought great effect to human being,and the waste water containing uranium from uranium mining and smelting has caused serious pollution to the soil.At present,phytoremediation is the most popular remediation method for uranium contamination,this method has the characteristics of green environment protection,less cost and good remediation effect.However,researches on microbial reprocessing technology for nuclide enriched biomass are rare.In order to solve this problem,a dominant strain is screened out from the natural environment in this paper,and UV mutagenesis is carried out to obtain the mutagenic strain;the optimal mutagenesis strain is determined by optimizing the culture conditions of mutagenic bacteria;In order to provide some theoretical and technical support for the post-treatment of nuclide enriched biomass,the paper studies the removal effect of uranium tolerance by dominant strains and the removal effect of uranium in wastewater by entrapped strains.The main results are as follows:（1）By sampling from paddy field,forest and cow dung,the strains that can degrade cellulose and produce cellulase are screened by Congo red selective medium.The strains with high ratio of transparent circle and colony and good growth are selected and identified.After UV mutagenesis,a cellulase producing strain JJ-1 is obtained.The results show that there are 8 cellulase-producing strains,among which the diameter of the transparent circle of JJ is the largest,and the diameter of the colony is 6 mm and 15 mm after 3 days of culture.Bacillus subtilis subspecies are identified by Biolog.The diameter of JJ-1colony is 11 mm and the diameter of transparent circle is 28 mm,which is significantly higher than that before mutagenesis.The activity of CMCA is nearly doubled to 0.1 U/m L compared with that before mutagenesis.After 4generations,the genetic stability of enzyme production is good,which indicates that bacterial JJ-1 has better cellulase production ability.（2）The strain JJ-1 is optimized by p H,time,temperature and inoculation amount.The results of orthogonal test shows that the OD₆₀₀00 value of JJ-1 was highest（0.2280）by 5%inoculation in BPG medium under the condition of p H7.0,35℃and 20 h,and the OD₆₀₀00 value by LB medium is 0.0191.The results show that the culture effect of strain JJ-1 on BPG medium is 10 times that of LB medium under the optimized conditions.（3）Bacillus subtilis with strong tolerance is screened by screening for removal of uranium.The experimental results show that uranium has little toxic effect on Bacillus subtilis at the same concentration.At 48h,the efficiency of Bacillus subtilis removing uranium reaches 90.7%.（4）The biosorption of uranium-contaminated wastewater by Bacillus subtilis/sodium alginate chitosan microcapsule is studied.The adsorption ability of Bacillus subtilis to uranium ion in aqueous solution is evaluated with Bacillus subtilis as control.The results show that the maximum value of adsorption of uranium by Bacillus subtilis/sodium alginate chitosan microcapsules at 20℃is300 mg/g and starts to decrease at 50℃.The removal rate of uranium by Bacillussubtilis/sodiumalginate-chitosanmicrocapsulesandsodium alginate-chitosan microcapsules at initial p H 6 are the highest.The adsorption capacity reaches 376.64 mg/g at the initial uranium concentration of 150 mg/L.In conclusion,the strain JJ,which is selected by experiment and study,can help industry and agriculture to utilize the resources and study the biodegradation of heavy metal enriched biomass to some extent.