Isolation And He-Ne Laser-induced Breeding Of The Phenol-degrading Strain Candida Tropicalis With High Activity

Phenol is present in the wastewater of many industries, including coke petroleum,pulp and paper, pharmaceutical, wood processing chemicals and paint solvent. Phenol,even low concentration, does harm to biomass for its toxic properties. With theprocess of economic, wastewater containing phenol has greatly thretoned environment.Because lots of aerobic microorganisms can utilize phenol as sole carbon, biologicalmethods of phenol removal are preferable in wastewater treatment process as arelatively low processing costs and low possibility of a secondary pollution.In our study, a strain of Candida tropicalis with high efficient phenol-degradingbacteria was isolated from acclimated activated sludge, and was identified as amember of Candida by the Chinese Academy of Agricultural Sciences.The phenol degradation was studied under the conditions of different centigrade,pH and initial phenol concentration. The results showed that 30℃ and pH 7.0 werethe optimal growth conditions. Furthermore, 2000 mg/l phenol could be entirelydegraded within 66 hrs.In order to enhance phenol degradation potential of Candida tropicalis, He-Nelaser irradiation was applied in our studies. And the mutant CTM2 was obtained. Thetests of phenol degradation demonstrated that CTM2 owned the higher phenoldegradation potential than its parent strain, and stable heredity.In contrast with wild type strain, phenol degradation potential of CTM2 wasobviously increased, which could degrade the phenol of 2600 mg/l within 84 hrs.The kinetics of cell growth and phenol biodegradation of CTM2 was investigated.Haldane's equation was adopted to describe the growth kinetics of CTM2 at 30℃ andpH=6.0: μ_X = 0.54 C_S /(6.70 + C S +C²_S/ 234.25). The phenol degradation processwas associated to the cell growth kinetics: μ_S = 0.8784 μ_X +0.2981h^-1. It wasindicated that the results simulated by the model agreed well with the experimentaldata. Higher values of the specific growth and degradation rates further demonstratedthe superiority of CTM2 for phenol degradation.