Study On The Selection Of The Mutants By Plasma Mutation And Its High Hydroquinone Degradation Character

Phenolic compounds are a class of strong toxic and refractory organic compounds frequently found in waste water. Since the phenolic compounds affect the growth and reproduction of aquatic organism and contaminates the drinking water sources, how to degradate such compounds in utility and safe has been an important problem regarded by human. Of all the methods of degradating phenolic compounds, biodegradation has been a main trend because of its low cost and no secondary pollution. For the strong toxicity of phenolic waste water, it is necessary to get one strain with fine degradation ability and high tolerance to phenolic compounds, which could elevate the efficiency of degradation.Based on the problem discussed above, this thesis studied the mutation of efficient strains of hydroquinone degradation. The bacteria source is S. marcescens AB 90027, which was mutated to obtain S. marcescens AB 90027 P15b-HQ3 by means of plasma induced mutation combining with the selection of hydroquinone tolerance. The results showed that the hydroquinone degradation ratio of the mutant above was higher than that of the parent strain.Co-metabolism is one of the most important methods for refractory organic compounds degradation.The study dealed with the degradation of hydroquinone by S. marcescens AB 90027 P15b- HQ3 cultured with different sources of carbon, nitrogen. The results showed that addition of carbon source accelerated the degradation of hydroquinone under co-metabolism process. Compared to other carbon sources studied, glycerine was the best carbon source for the degradation of hydroquinone. After 14 days'hydroquinone degradation, the degradation ratio of hydroquinone was 80.4% and the half-life of hydroquinone was 3.5 d while the concentration of glycerine was 2 g/L. Supplement of peptone hindered the degradation of hydroquinone , however, peptone further decurtated degradation of hydroquinone. It is available to accommodate the balance of both as the concentration of peptone was 1.5 g/L. The optimum degradation mediums were glycerine 2 g/L, peptone 1.5 g/L, Mn2+ 0.1 mg/L, Fe2+ 0.1 mg/L, Cu2+ 0.1 mg/L, Ca2+ 10 mg/L while the degradation ratio of hydroquinone reached to 80.5% 9 days'degradation. The yield was enhanced and the degradation time was shortened by optimization of culture media and degradation conditions in flasks, which provided dependable rationale for co-metabolism of phenolic compounds.The addition of H2O2 profited for hydroquinone further degradation, and there was an optimum value at the condition of degradation: 3 mL 10%H2O2 could removal most 100 mL 2000 mg/L hydroquinone and the degradation ratio was 97.6%. Besides, compared to the method of dropwising H2O2 in batch, dropwising H2O2 at one time had the same effect in hydroquinone degradation, and the degradation ratios of both were between 96.9%-97.4%.