Biodegradation of m-cresol in alkaline wastewater by resting photosynthetic bacteria

Abstract

The application of various micro-organisms to metabolize organic compounds is one potentially effective method in treating hazardous and toxic wastewater. The effects of doses of cells, pH, initial substrate concentrations, and the addition of metal ions (Mn2+ and Cu2+) on m-cresol biodegradation by the resting cells (non-growth cells without immobilizing) of photosynthetic bacteria (PSBr) are investigated on a rotary shaker at 120 rpm at 30°C. The maximum biodegradation rate for a 200 mg/L m-cresol solution was 98% with a PSBr dose of 0.17 g/L, pH 7.5 at 30°C in dark conditions. The degradation capability of PSBr 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. Specific degradation rates were fitted with the Haldane kinetic model. The parameter values were; rmax = 0.05/h, Km = 254.15 mg/L, and Ki = 112.18 mg/L, with a coefficient of determination (R2) greater than 0.89. Our results suggest that PSBr shows good potential for degrading m-cresol in wastewater.