[Biodegradation of pyridine by Shinella zoogloeoides BC026]

A bacterial strain BC026 capable of utilizing pyridine as its sole source of carbon and nitrogen was isolated from the activated sludge in a coking wastewater treatment plant. The bacterium featured flocculability and antibiotic resistance to kanamycin, ampicillin and spectinomycine. It could grow well in Ashby nitrogen free culture medium. The strain was identified as Shinella zoogloeoides according to the results of 16S rRNA sequence analysis and Biolog microbial identification system. The experiments of pyridine biodegradation by the pure culture showed that pyridine of 400 mg/L could be degraded completely in 17 h under the condition of inoculum 0.1 g/L, 30 degrees C, 180 r/min and pH 7. BC026 could keep high degradative activity in mineral salt medium containing pyridine with a concentration ranging from 99 mg/L to 1 806 mg/L. Higher initial concentration of pyridine caused repression on BC026 to a certain extent, however, the degradation rate became faster after the strain had been accommodated. The optimal conditions for the degradation were 30-35 degrees C and pH 8. The research on metabolic pathway of pyridine by BC026 indicated that the first step of pyridine degradation was C-N bonds cleavage, generating NH4+ and glutaraldehyde. Then glutaraldehyde was oxidized into glutaric acid, and finally into CO2 and H2O. 59.5% nitrogen from pyridine was transferred into ammonium in the whole degradation.