KINETICS OF PHENOL BIODEGRADATION BY PROVIDENCIA RETTGERI

Providencia rettgeri, Providencia stuarti and Enterobacter cloaceae had been isolated from phenolic wastewater. The isolates exhibited differences in their phenolic tolerance and biodegradation activity. Out of 16 isolates, 9,4 and 3 of them tolerated phenol to 0.5 ,1.0 and 1.5% w/v phenol, respectively. Providencia species exhibited a potent biodegradability than Enterobacter cloaceae aganist phenol. The retaining of this character was not manifested by most of these isolates. Three isolates of Providencia rettgeri represent the most active phenol biodegradable isolates, were capable to utilize and degrade phenol up to concentrations 600, 800 and 1000 µg/ml and 84, 88.8 and 100% of phenol was degraded, respectively, after 5 days. The kinetic parameters of phenol biodegradation indicated that the maximum specific growth rate is inversely proportional with the bioconversion and indicates a high affinity of the organism for the substrate. However, higher concentration (> 1.5 mg/ml) were shown to be inhibitory for metabolism and growth, The rate of phenol biodegradation increased with tolerated moderate concentration of the substrate, time of incubation (3-5 days) and optimal temperature (at 35°). Addition of glucose or yeast extract, although enhanced the growth rate, yet it retarded the biodegradation. These kinetic parameters can be used to define the optimal conditions for the removal of phenol in biological treatment systems.