Pseudomonas alcaligenes was found to be an effective biodegrader of 2,4-dichloropjenol(DCP), a waste product of pharmaceutical industries, at pH 7 and 35 °C after ultraviolet light exposure . The chlorinated aromatic compound 2,4-dichlorophenol is an environmental pollutant that can be synthesized into larger phenols, pesticides, and herbicides. Pseudomonas alcaligenes extracted from sewage sludge were tested for growth and biodegradation based on various 2,4-DCP concentrations, UV radiation exposure, temperature at pH 7, and pH in 25 °C. The amount of 2,4 DCP that degraded from Pseudomonas alcaligenes correlated significantly with increasing values of these four factors, in particular the amount of 2,4-DCP that degraded increased significantly after 144 hours of UV radiation exposure (Elkarmi et al. 2009). The degradation of 2,4 DCP by Pseudomonas alcaligenes would be highly effective in bioremediation programs for reducing the amount of pharmaceuticals in the environment, especially in sewage treatment plants where most pharmaceuticals are not eliminated during the cleaning process. — Kevon White
Elkarmi, Ali., Abu-Elteen K., Atta A., Abu-Sbitan N., 2009. Biodegradation of 2,4-dichlorophenol originating from pharmaceutical industries. African Journal of Biotechnology 8, 2558–2564.
Ali Z. Elkarmi and colleagues from Hashemite University extracted and identified Pseudomonas alcaligenes from the wastewater of two pharmaceutical and healthcare industries. The sewage was centrifuged for 30 minutes to obtain 200 mg of sludge, which was then added to sterilized flasks containing 20 ml of chlorophenol enrichment media and 100 mg/l 2,4-dichlorophenol. The mixture along with a second mixture from 50 ml of nutrient broth and 0.5 ml of the first suspension incubated were incubated 30 °C for four days. Nutrient agar plates containing 100 ml/I 2,4-DCP were inoculated with 0.3 ml of the second mixture and both were incubated at 37 °C for four days. The results were sent to the Jordan University hospital, which confirmed the identity of the bacterial species Pseudomonas alcaligenes. The colonies of Pseudomonas alcaligenes were placed in nutrient agar plates of 1 g/l cetrimide where they were tested for 2,4-DCP concentrations in increments of 20 mg/l starting from 120 mg/l to 300 mg/l. Isolated colonies of Pseudomonas alcaligenes were then subjected to UV radiation for 24, 48, 72, and 96 hours in 2,4-DCP concentrations at increments of 20 mg/l starting from 240 mg/l to 400 mg/l. The UV irradiated samples were then cultivated in a bioreactor were biodegradability of 340 mg/l 2,4-DCP was tested from temperatures of 25, 30, 35, and 40 °C and pH values ranging of 6.5, 7.0 and 8.0. The final results were compared for statistical significance using one-way ANOVA test.
Without UV radiation the amount of bacteria that grew in the 2,4-DCP culture decreased with increasing concentration. From 180 mg/l to 220 mg/l 2,4-DCP, the bacteria exhibited weak growth decreasing from 9.60 to 6.07 log10 of CFU/ml respectively. The amount of 2.4-DCP after UV radiation was added, however, increased the limit for tolerance and biodegradation of 2,4-DCP significantly; at a concentration of 200 mg/l of 2,4-DCP, the growth of bacteria increased from 8.40 mg/l to 9.08 mg/l log10 of CFU/ml. After UV radiation exposure the limit for the concentration of 2,4-DCP to decrease growth was raised to 380 mg/l at 6.80 log10 of CFU/ml. At a pH of 7.0, growths were best at a temperature of 35 °C after 168 hours. At a temperature of 25 °C, growths were best at a pH of 7.0 after 168. The ANOVA test indicated that there were significant correlations between pH, UV radiation, concentration of 2,4-DCP and temperature. A possible use for the Pseudomonas alcaligenes would be in bioremediation and sewage treatment where pharmaceuticals are often not eliminated from the wastewater treatment process.