Kinetics of biodegradation of p-nitrophenol by different bacteria

Three bacterial species, i.e., Ralstonia sp. SJ98, Arthrobacter protophormi ae RKJ100, and Burkholderia cepacia RKJ200, have been examined for their ef ficiency and kinetics behavior toward PNP degradation. All the three bacter ia utilized PNP as the sole source of carbon, nitrogen, and energy. The rat es of radiolabeled [U-C-14]PNP degradation by all the bacteria were higher in the nitrogen-free medium compared to the medium with nitrogen. The appar ent K-m values of PNP degradation by SJ98, RKJ100, and RHJ200 were 0.32, 0. 28, and 0.23 mM, respectively, as determined from the Michaelis-Menten curv es. The maximum rates of PNP degradation (V-max) according to Lineweaver-Bu rk's plots were 11.76, 7.81, and 3.84 mu mol PNP degraded/min/mg dry biomas s, respectively. The interpretation drawn from the Lineweaver-Burk's plots showed that the PNP degradation by SJ98 was stimulated by 4-nitrocatechol a nd 1,2,4-benzenetriol. Benzoquinone and hydroquinone inhibited PNP degradat ion by RKJ200 competitively and competitively, respectively, whereas in the case of RKJ200, benzoquinone and hydroquinone inhibited PNP degradation in an uncompetitive manner. beta-Ketoadipate did not affect the rate of PNP d egradation in any case. (C) 2000 Academic Press.