Biodegradation of pyridine by pimelobacter sp.

Abstract

A bacterial strain capable of degrading pyridine was isolated from a retort water treatment column(RWTC) by enrichment culture techniques. The micro organism was aerobic, Gram-positive, pleomorphic, nonsporeforming and had a subpolar flagellum. The strain contains LL-diaminopimelic acid, galactose, and glycolyl residues in the cell wall. The G+C content of DNA was 72.5 mole \%. The major manaquinone was MK-8($H_4$) and the cellular fatty acid composition was complex type. Based on the morphological, physiological and chemotaxonomic characteristics, the strain was identified as Pimelobacter sp. The microorganism could oxidize pyridine for energy, nitrogen and carbon sources. The nitrogen in pyridine was released as ammonium. The microorganism could decrease TOC(total organic carbon) of the retort waters and catabolize other aromatics. These results indicates this organism could be well adapted to retort waters. When pyridine was present, catalytic activity to pyridine was induced. Pyridine has the effect of changing the fatty acid composition of the membrane. The result of these changes was an increase in the degree of saturation of lipids probably in order to compensate an increase of fluidity of the membrane induced by the pyridine. In small inoculum size, readily available nutrients stimulated growth rate but the specific degradation rates were inverse to the growth rate. Ammonium ion increased both growth rate and specific degradation rate. In large inoculum size, the specific degradatrion rate was not decreased by these nutrients, and ammonium ion had no effect on pyridine degradation. In immobilized cells degradation rate was limited by diffusion at low concentration of pyridine, but at higher concentration of pyridine immobilized cells were more tolerant than free cells. On semicontinuous cultures immobilized cells could maintain catalytic activity for 70 hours during six times of the replenishment of the media at 1 g/L of pyridine conc. and retained cata...