Kinetics of phenanthrene degradation by Staphylococcus sp. strain PN/Y involving 2-hydroxy-1-naphthoic acid in a novel metabolic pathway

Staphylococcus sp. strain PN/Y isolated from creosote-contaminated soil, was previously reported to degrade phenanthrene as sole source of carbon and energy. Unlike other phenanthrene degraders, Staphylococcus sp. PN/Y degraded phenanthrene by a novel pathway involving 2-hydroxy-1-naphthoic acid (2H1NA), which was further metabolized by unique meta-cleavage dioxygenase, ultimately leading to TCA cycle intermediates. In the present study, kinetics of phenanthrene degradation and the dynamic fate of the key intermediates, 2H1NA, salicylic acid and catechol were demonstrated. When cells were grown on 50, 100, 200, 500 and 1000 mg l−1 of phenanthrene, the doubling time was 31.55, 30.2, 29.32, 26.84, 25.22 h and the specific growth rate was 0.0314, 0.0331, 0.034, 0.0372 and 0.0396 h−1, respectively. At a concentration of 1 g l−1 of phenanthrene, the maximum accumulation of 2H1NA was found to be 323 mg l−1. In addition, 2H1NA utilized by Staphylococcus sp. PN/Y as sole carbon source, the growth yield at 96 h was 445, 557, 560, 480, 419, 334, 212 and 66 mg of protein (g 2H1NA)−1 when cells were grown on 50, 100, 200, 400, 500, 650, 800 and 1000 mg l−1 of 2H1NA, respectively. Growth was found to be inhibited at initial higher concentration of 2H1NA, which may attributed due to concentration-dependent toxicity of 2H1NA and/or the toxicity of its decarboxylated metabolite, 2-naphthol.