Study On Biodegradation Of Phenol And M-Cresol By Photosynthetic Bacteria

In this paper, photosynthetic bacteria (PSB) with high degradation efficiency for phenol and m-cresol were obtained by acclimation of gradual increase of m-cresol, and their morphological and some physiological biochemical characteristics were identified. The biodegradation characteristics of PSB for simulated phenol and m-cresol containing wastewater were investigated. It includes the following two aspects:First of all, the biodegradation characterizations of m-cresol by PSB under different inoculum size, initial pH and m-cresol concentration in the darkness were investigated. Meanwhile, the effects of adding different concentrations of Mn2+and Cu2+on m-cresol biodegradation were also examined. Results showed that the maximum biodegradation rate for a200mg/L m-cresol solution was98%with inoculum size20%, pH7.5under dark conditions after72h of incubation. Furthermore, the degradation capability of PSB was drastically reduced in the presence of Mn2+or Cu2+, and the inhibitory effect of Cu2+was greater than that of Mn2+for the same concentration. The degradation process was fitted with the Haldane kinetic model. The parameter values were rmax=0.05h-1, Km=254.15mg/L, Ki-112.18mg/L, and the correlation coefficients was0.89.Next, the biodegradation characterizations of phenol by PSB under different illumination density, initial pH, inoculum size and initial substrate concentration were investigated. Meanwhile, the effects of adding different concentrations of Mn2+, Cu2+and sodium acetate on phenol biodegradation were also examined. Results showed that the maximum biodegradation rate for a500mg/L phenol solution was65.4%with inoculum size10%, pH8.0under dark conditions after72h of incubation. Addition of Mn2+at the tested concentrations could accelerate the degradation process but not for the addition of Cu2+.Furthermore, the biodegradation was accelerated at low concentrations of sodium acetate but not for high concentrations. The degradation process was fitted with the Haldane kinetic model. The parameter values were rmax=0.17h-1, Km=858.66mg/L, Ki=198.15mg/L, and the correlation coefficients was0.96.By comparison, we proposed that the degradation mechanisms of m-cresol and phenol by PSB were different. PSB degraded m-cresol by enzymatic reaction mechanism but growth mechanism for phenol.m-Cresol has the extra methyl group in benzene ring, which may seriously inhibit the growth of PSB.