Breed Of Phenol-degrading Microorganism With N～+ Ion Induced Mutation

Phenol and its ramification are a class of strong toxic and refractory organic compounds frequently found in wastewater. The phenolic pollutants including phenol, cresol, resorcin and other phenolic compounds are main contaminants in wastewater from oil refineries, coke plants, coal gas factories and other chemical plants. Volatile phenol is the most toxic among these phenolic compounds. When it enters into organism, it will cause the protein denaturation and coagulation. Since the phenol affects the growth and reproduction of aquatic organism and contaminates the drinking water sources, the discharge of phenolic wastewater must be strictly ruled, otherwise will severely pollute the environment.For the difficulty of the degradation of phenolic wastewater, the breeding of efficient strains is a key problem in biodegradation. Consequently, the strains should have high capability of phenol degradation and better adaptability of impact load to enhance the efficiency of phenol degradation.Based on the problem discussed above, this thesis studied the culture and mutation of efficient strains of phenol degradation. The bacteria source is the active sludge from a coking wastewater treatment plant. After domesticating the strain, ten strains were selected to degrade the wastewater of various phenol densities. Then three kinds of bacteria with powerful phenol degrading capability, i.e. A,C and E, were selected. An efficient strain KE2 was obtained from the best strain E by ion beam implantation. The degradation characteristics of all selected strains were investigated. Phenol degradation experiments of mixed strains and laboratorial simulated wastewater were carried out to determine the growth characteristics and optimal growth condition of ion beam mutated strain. The main results were summarized as follows:1. Ten bacterial strains which could remove phenol were isolate from a batch culture and the sludge from iron plant. The removal abilities to phenol of these strains were compared using 4-amino-antipyrine spectrophotometry. Then strain E was selected as initial mutation strains for its best removal ability. Strains A and C were selected as comparison strains. The removal rate of E was 91.30%, 82.04%, and 63.22% after 12h aerobic culture in the culture solution in which the density of phenol was 500mg/L, 1000mg/L and 1500mg/L respectively.2. Some mutated strains were obtained after N⁺ ion beam implantation. The best implantation dosage was determined as 18.4×10¹⁴N⁺/cm² by the livability and positive mutation rate. The mutated strain with best removal ability was named KE2, and its removal rate was 91.30%, 82.04%, and 63.22% at same condition. The removal rate of KE2 was higher than that of E, and the properties of continual inoculation was stable. The strains E and KE2 were identified as Pseudomonas.sp.3. The optimal temperature to four strains was 30℃. The optimal reproduction time to KE2 was 1d, it was 2d to A,E and 3d to C. The optimal pH to four strains was 7. The optimal OD to C,E,KE2 was 0. 6 and it was 0. 4 to A。4. The concentration of carbon source (glucose) would affect the removal ability of strains. The growth of strain increased with the concentration of external carbon source. The optimal concentration of carbon source was 1000mg/L. The strain growth and removal ability to phenol was high with optimal concentration of carbon source.5. The experimental results of phenol degradation using mixed strains of KE2, A, C, and E show that under the aerobic condition and the lower density of phenol (500mg/L), there was no significant vary between the single strains and mixed strains. When the density of phenol increased to1000 mg/L or 1500mg/L, the removal ability of mixed strain was higher than the other single strains. The removal ability was various for different mixtures and symbiosis play an important role in higher density of phenol.6. The growth condition of mutated strain KE2 was optimized through orthogonal experiment. Three facts of temperature, pH, and concentration of carbon source have effect on Phenol biodegradation and follow the sequence: temperature > carbon source concentration > pH. The optical condition of Phenol biodegradation are determined as 1000mg/L , pH7.0 and 30℃.7. Under the optimal combination of temperature, pH and concentration of carbon source, some laboratorial simulation experiments were carried out. The experimental results show that the performance of the group containing mutated strain is better the performance of CK. When the density of phenol was 500mg/L, the removal rate of mutated group was 100% after 9h degradation and that of CK was 84%. When the density of phenol was 1000mg/L, the removal rate of mutated group was 100% after 12h degradation and that of CK was 52%.