Biphenyl Degrading Bacteria, Identification And Degradation Characteristics

Modern industry produced a variety of aromatic compounds and resulted in the environmental pollution. In the general regulation of aromatic pollutants, human beings can make use of physical, chemical and biological means, but the widespread degradation of these methods was not thorough and easy to cause secondary pollution. Microbial treatment was a method of low cost, high efficiency, no secondary pollution and easy operation. Therefore, screened the efficient degradation bacteria, studyed the degradation characteristics and its related enzymes, and applied into the environment had an important theoretical and practical significance.Biphenyl was an aromatic compounds, it was refractory, volatile, and soluble in acetone, ethanol and other organic solvents. Biphenyl was widely used, it was coal tar, crude oil and natural gas components. Because of the extensive application, biphenyl and its physiological toxicity had been an in-depth research, many inhaled could cause muscle atrophy, central nervous system and liver damage. Biphenyl was suspected mutagens, it could generate to PCBs in the presence of an appropriate catalyst. Because of the gradual accumulation in vivo biology, PCBs were absorbed by skin, lung and gastrointestinal system, then flowed into the liver, a variety of muscle and adipose tissue.A biphenyl-degrading bacterial strain was isolated from the mountain area of southern part of Jinan by selective enrichment culture. The strain was able to grow on biphenyl as a sole carbon and energy source for growth, and named as LB07. It was identified as Bacillus megaterium based on its morphological, physio-biochemical identification and 16S rDNA sequence analysis.The factors influencing the strain's biphenyl degrading ability, such as pH, temperature, initial biphenyl concentration, the volume of medium, inoculum size and reaction time were studied. The optimal conditions for the degrading biphenyl were chosen by orthogonal experiment. The results showed that the optimum conditions were as follows: mass concentration of substrate was 150mg/L, temperature was 35℃, pH was 6.5, the volume of medium was 50mL/250mL, reaction time was 10days, under which the biodegrading rate reached to 94%.By pure culture, ultrasonic fragmentation and centrifuge separation, degradation enzyme for biphenyl were extracted from the isolated stain LB07. Degradation characteristics of biphenyl by enzyme were determined. The crude enzyme had optimum pH 8.0 and temperature 37℃for degradation of biphenyl, And it can keep stable under pH7.0-9.0 and 30℃-40℃. From the figure of Lineweaver-Burk, it was found that the Vmax for the degradation of enzyme was 88.49nmol/mL·min and the Michaelis constant(Km) was 228.12nmol/mL.The strain can also use phenanthrene, naphthalene and salicylic acid as carbon sources. For example, strain LB07was capable of degrading phenanthren via the meta-cleavage pathway. It was found that activity of the ferment liquid was much lower than that of the broken cell, which proved that this enzyme was in the cell.