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

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.

Pyridine Degradation by Suspensions and Biofilms of Achromobacter pulmonis PNOS and Burkholderia dolosa BOS Strains Isolated from Activated Sludge of Sewage Treatment Plants

Bacterial strains capable of degradation of 0.8-15.8 g/1 pyridine hydrochloride have been isolated from activated sludge of municipal biological treatment plants in Perm (BOS) and local treatment facilities of the LUKOIL-Permnefteorgsintez enterprise (PNOS). The strains were identified as Achromobacter pulmonis and Burkholderia dolosa. The optimal pyridine concentration for the growth of the isolated strains was 4.0 g/1. The pyridine degradation during the A. pulmonis PNOS and B. dolosa BOS cultivation on a medium with ammonium chloride and glucose and without additional nitrogen or carbon sources was studied. It was shown that the strains are able to accumulate biomass in a medium with pyridine as the sole carbon and nitrogen source; the addition of glucose to the medium (1 g/L) accelerated the pyridine degradation by A. pulmonis PNOS, but inhibited the process carried out by B. dolosa BOS. B. dolosa BOS and A. pulmonis PNOS biofilms efficiently utilized pyridine during growth on basalt and carbon fibers; the highest rate of pyridine utilization (1.8 g /(L day)) was observed in A. pulmonis PNOS biofilms on basalt fibers. pyridine, biodegradation, activated sludge, biofilms, Achromobacter pulmonis, Burkholderia dolosa The authors grateful to Dr. I.I. Tchaikovsky, Head of the Laboratory of Geology of Mineral Deposits of the Mining Institute, a branch of the Perm Federal Research Center, for help with electron microscopy of the samples. This work was carried out as part of a state assignment on the topic « Study of the Functional and Species Diversity of Microorganisms Useful for Ecocenoses and Human Practical Activity», registration number R&D AAAA-A19-119112290008-4.