Selective acceleration of 2-hydroxyl pyridine mono-oxygenation using specially acclimated biomass.

Biodegradation of pyridine starts with two mono-oxygenation reactions, and 2-hydroxyl pyridine (2-HP) accumulates as pyridine is mono-oxygenated in the first reaction. The accumulation of 2-HP inhibits both initial reactions. Therefore, selective acceleration of the second mono-oxygenation reaction should significantly enhance pyridine transformation and mineralization. Activated-sludge biomass was separately acclimated with pyridine or 2-HP to produce pyridine- and 2-HP-acclimated biomasses. The pyridine-acclimated biomass was superior for pyridine biodegradation, but the 2-HP-acclimated biomass was superior for 2-HP biodegradation. As a consequence, the pyridine-acclimated biomass by itself achieved faster mono-oxygenation of pyridine to 2-HP, but 2-HP accumulated, which limited mineralization to 60%. In contrast, mineralization reached 90% when one-third of the pyridine-acclimated was replaced with 2-HP-acclimated biomass, because 2-HP did not accumulate during pyridine biodegradation. The lack of 2-HP accumulation relieved its inhibition: e.g., the pyridine removal rates, normalized to the mass of pyridine-acclimated biomass, increased from 0.52 to 0.57 mM0.5⋅h-1 when one-third of the pyridine-acclimated biomass was replaced by 2-HP-acclimated biomass. Phylogenetic analysis showed that microbiological communities of pyridine-acclimated biomass and 2-HP-acclimated biomass differed in important ways. On the one hand, the 2-HP-acclimated biomass was richer and dominated by a rare biosphere, or genera having <0.1% of total reads. On the other hand, the most-enriched genus in the pyridine-acclimated community (Methylibium) is associated with the first mono-oxygenation of pyridine, while enriched genera in the 2-HP-acclimated community (Sediminibacterium and Dokdonella) are associated with the second mono-oxygenation of pyridine.