Study On Improving Efficiency Of Bacteria For Biological Nitrogen Removal By Cell Fusion

Five bacteria possessed ability to removal nitrogen were isolated from active sludge by limiting dilution assay and flat crossed seperation.Three of them are ammonia-oxdizing bacteria, named A1, A2, A3; one of them is nitrobacteria, named B1 and one of them is denitrobacteria, named C1. Classify these bacteria, A1 is Nitosococcus, A2 is Filamentous bacteria, A3 is Nitrosomonas, B1 is Nitrobacteria, C1 is Bacillus. Through experimentation, the optimal condition of protoplast fusion as follows: PEG 40%,; time of fusion, 4 min; Ca2+, 0.015mol/L; PH, 10.0; cell wall regeneration inducer, 200 uL; UV-irradiation on the parent protoplast, 60s. After UV-irradiation, three single resistance mutants were obtained, named K-A1, K-B1, K-C1. Then using these three mutants as the parent strain to process protoplast fusion and the medium containing two kind of antibioticses to select the fusion. After these steps, we obtain two fusion, named CO1 and CO2. Classify them, CO1 is Bacillus, CO2 is Nitosococcus. And the nitrogen removal efficiency of CO1 is 27.4% higher than its parent strain, but the efficiency of CO2 has not obvious chang.The result of this experimentation show that the technique of protoplast fusion could be used to breed high efficiency degradation strain for cleaning wastewater. And also show that this technique has some deficiency, such as the success rate is not high; although succeed, the degradation rate of the fusion might not chang.