| This thesis focuses on the key technical problems of how to deal with uranium and its associated heavy metal hyperaccumulators,using a set of composite cellulose-degrading bacteria of tolerant uranium and associated heavy metals that were screened and assembled in the earlier experiment to carr y out solid state fermentation for straw containing uranium(simulated hyperaccumulator plant).The optima l condit ion for producing cellulase from solid-fermented uranium-bearing stalks was obtained by single-factor and orthogonal experiments.The dry matter content and composit ion of straw after 15 days solid-fermented uranium-bearing stalks were also studied.By using the triple quadratic orthogonal rotation design,the characteristics of cellulase produced by solid fermented uranium-manganese-arsenic stalks were preliminary studied.These results can provide some theoretical and technical support for the volume reduction of hyperaccumulator plants.The results were as follows:(1)The optimum condition for producing cellulase from compound strain solid fermentation uranium-bearing stalks was as follows: w ith 25 grams of wheat straw containing U as the carbon source,nitrogen source was 2% ammonium sulfate nutrient solut ion,inoculum size was 4 mL,fermentation temperature was 40 ?,the init ial p H was 7 and the solid-liquid ratio was 1:5.The solid-fermented uranium-containing stalks had a carboxymethylcellulase activity(C MC A)of 709.77 IU and a filter paper enzyme activity(FPA)of 650.74 IU under the optimum condition.(2)The weight lessness rate and lignocellulose degradation rate of the straw after 15 days of composite bacteria solid fermentation with uranium-containing straw under different conditions were as follows: under the optimum nitrogen source and concentration,the weight loss rate,cellulose degradation rate,hemicellulose degradation rate and lignin degradation rate of straw were respective ly 50.25%,55.46%,60.48% and 34.19%;under the optimal inoculum size,the weight loss rate,cellulose degradation rate,hemicellulose degrada tion rate and lignin degradation rate of straw were respectively 52.63%,60.19%,66.39% and 36.58%;under the optimum temperature,the weight loss rate,cellulose degradation rate,hemicellulose degradation rate and lignin degradation rate of straw were respective ly 52.98%,59.30%,66.21% and 35.96%;under optimum initia l p H condit ion,the weight loss rate,cellulose degradation rate,hemicellulose degradation rate and lignin degradation rate of straw were respective ly 53.13%,60.29%,65.61% and 36.54%;under the optima l solid-liquid ratio condit ion,the weight loss rate,cellulose degradation rate,hemicellulose degradation rate and lignin degradation rate of straw were respectively 56.02%,63.30%,69.37% and 37.22%;with 25 grams of wheat straw containing U as the carbon source,2% ammonium sulfate nutrient solut ion as nitrogen source,inoculum size of 4 mL,fermentation temperature of 40 ?,init ial p H of 7 and solid-liquid ratio of 1:5,the weight loss rate,cellulose degradation rate,hemicellulose degradation rate and lignin degradation rate of straw were respective ly 56.56%,67.13%,69.25% and 37.32%.(3)The characteristics of cellulase produced by complex bacteria solid fermentation uranium-manganese-arsenic straw: under the 50~ 400 mg/kg combined pollut ion with uranium,manganese and arsenic,U(r=-0.2569)and Mn(r=-0.0515)had a negative effect on the C MC A production of compound bacteria,As(r=0.5162)showed a significant positive effect on the CMC A production of composite strains.Under the 50~ 400 mg/kg comb ined pollut ion with uranium,manganese and arsenic,U(r=-0.2569)and Mn(r=-0.0515)had a negative effect on the FPA production of compound bacteria,As(r=0.5162)showed a significant posit ive effect on the FPA production of composite strains. |
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