Microbial Degradation of Pyridine by Co-culture of Two Newly Isolated Strains, Arthrobacter  sp. Strain PDC-1 and Rhodococcus  sp. Strain HPD-2

Abstract Pyridine is one of the most widespread heterocyclic contaminants. Microbial degradation of pyridine seems quite promising for its safety and efficiency. A bacterial consortium, which could use pyridine as the sole source of carbon, nitrogen, was obtained from the petroleum-contaminated soil from Liao River estuarine wetland. Two pyridine degrading strains, designated as PCD-1 and HPD-2, were isolated from the bacterial consortium. PCD-1 was identified as an Arthrobacter , and HPD-2 was identified as the Rhodococcus genus. The effects of pH, temperature, and pyridine concentration were investigated, and the optimum growth conditions for two strains were similar at pH 7.0 and 30°C. The co-culture of the two strains, CoPD, has better degradation efficiency compared with the individual strain. Haldane's inhibitory growth kinetics equation could be fitted to the growth of co-culture CoPD well for the entire concentration range. The kinetic constants obtained were μ max = 0.141 h -1 , K s = 37.9 mg/L, and K i = 3830 mg/L. Co-culture CoPD was able to remove more than 98% pyridine with an initial pyridine concentration of 5,000 mg/L within 120 h. Strain PCD-1 and HPD-2 have a novel pyridine degradation pathway different from the reported pathways. Major intermediates of pyridine degradation by two strains, including 2,5-pyrroldione, maleic semialdehyde, furanone, and butyrolactone, were identified using LC-MS analysis. CoPD is a promising tool for the treatment of wastewater containing pyridine, and this study contributes to the knowledge of the pyridine biodegradation by bacterial consortium.