The Screening Of Cynide-Degradation Microorganisms And Its Immobilization

The treatment of cyanide is essential for its high toxicity and popular use in many industrials. Biodegradation plays an important role in cyanide-containing wastewater treatment. The screening of highly-effective-cyanide-degradation strains and its immobilization were investigated as follows, (1) the selection and determination of analytic methods of cyanide appropriate for the different systems, (2) the building of a efficient, simple and convenient screening model to obtain an aimed strain and the optimization of cell growth and degradation conditions such as shaker rotation, pH value and temperature, (3) the selection of immobilization methods and comparison of degradation characteristic for the immobilization with free cell.At first, photospectrometer and ion selective electrode were used for analysis of cyanide respectively and the same results were obtained. A highly effective screening model was built, in which enrichment was conducted by adding a definite amount of cyanide into the innutrient medium. Forty-nine kinds of cyanide-resistant strains were isolated from twenty samples of soil, among which twenty-nine kinds of strains showed the cyanide-degradation ability and the bacterial strain numbered DC02 was the best.The examination of cell growth and degradation characteristics of strain DC02was conducted in the further studies. The strain had a high cyanide-resistant ability that it could grow in the present of cyanide up to 1000 mg/L CN-. It was advantages to conduct the cell culture with 20ml medium in 250ml flock and the optimum culture and biodegradation conditions were determinated to be 120rpm, pH 8.0 and 30 C and the biodegradation rate for the wastewater of 500 mg CN- / L could reach to 99% in 10h. Metal-cyano complexs could also be degraded by DC02 with the conversion of96% in 12h for the wastewater of 500mg CNVL.The experiments of the immobilization cells on sodium alginate and zeolite carrier showed that two kinds of immobilization cells display the nearly same degradation activity and curve as the free cell respectively. The immobilization process with zeolite as the carrier was more simple than one with sodium alginate. The optimum reaction conditions for immobilized cells were 30癈 and pH 8.0. In the immobilization process, growth of cells on the zeolite and suspended cells were synchronous and biomass adsorbed by zeolite was calculated to be 0.228g dry weight/g. The immobilized cells could be reused at least 5 times. Cyanide degrading was also conducted in the open system and it has been found that the stability of biological system could be maintained in the present of cyanide and the biodegradation rate for the wastewater of CN" of 500mg/L reach to 99% in 6h.