Characterization of Novel 4–<i>n</i>–Butylphenol– Degrading <i>Pseudomonas veronii</i> Strains Isolated from Rhizosphere of Giant Duckweed, <i>Spirodela polyrrhiza</i>

Abstract

Novel bacteria capable of utilizing 4-n-butylphenol (4-n-BP) as the sole carbon source were isolated from rhizosphere of giant duckweed, Spirode/a po/yrrhiza. These bacteria were identified as Pseudomonas veronii. One of the isolates, P. veronii designated strain nBPS, could completely degrade 4-n-BP up to 1.0 mM. The strain was capable of growing on 4-n-BP at temperature of 10-30 °c, pH of 5-8 and NaCI concentration of 1.S % or less, and the optimal temperature, pH and NaCI concentration were 2S °c, 6.0 and 0.1 %, respectively. Specific 4-n-BP-degrading activity of strain nBPS followed the Michaelis­ Menten kinetics, with the maximal degradation rate of 0.2S8 mmollmg-celllh although the activity declined at ~0.07S mM probably due to inhibitory effect of high substrate concentration. Based on the metabolites identified by GC-MS, the pathway of 4-n-BP degradation by strain nBPS was proposed: 4-n-BP is initially hydroxylated to 4-n-butylcatechol, and subsequently 4-n-butylcatechol is metabolized via the meta­ cleavage pathway. 4-n-BP-degrading enzyme of strain nBPS was very effective to 4-n-alkylphenols (4-n-APs) with short and medium alkyl chain (C2-CS) and effective to 4-n-APs with long alkyl chains (C6-C9) although the degradation ratio declined with increase of length of alkyl chain.