Isolation and physiology of a dimethyl phthalate degrading bacterial strain YZ2

Abstract

AbstractA bacterial strain YZ2 was isolated from digested sludge of Sibao wastewater treatment plant located in Hangzhou, China and was characterized using morphological, biochemical, and physiological characteristics. The microbial colonies on LB medium were yellowish, 3–5 mm in diameter and convex in the center. The individual cells of isolate were short rods, measuring 0.6 × 0.9 – 1.0 × 1.5 μm with small side projections, clubbed ends, and without any filaments. Individual cells were gram‐positive. Based on 16S rDNA (1438 bp) sequence analysis, isolate was identified as Rhodococcus sp. isolate YZ2 capable of dimethyl phthalate (DMP) biodegradation under nitrate‐reducing conditions. Results of batch experiments showed that the degradation of DMP was optimum at pH 7.5 and 31°C. In the range of 70–600 mg l−1, the initial DMP concentrations showed very high correlation with biodegradation rate (0.9773 < r2 < 0.9941), suggesting a first‐order reaction. The half‐life value showed an increase from 0.89 to 2.22 days during biodegradation of various DMP concentrations. HPLC and LC‐MS analysis showed that MMP and PA may be the first and second intermediates, respectively, during DMP biodegradation under anoxic conditions. PA did not accumulate in the culture liquid, while MMP could not be mineralized by Rhodococcus sp. YZ2. © 2007 American Institute of Chemical Engineers Environ Prog, 2007