Effect of Culture Condition and Growth Kinetics on Phenol Biodegradation by an Indigenous Rhodococcus pyridinivorans Strain PDB9T NS-1

The US Environmental Protection Agency listed phenolic compounds as priority pollutants, and their occurrence in water systems poses serious health risks to humans and other living species. The culture conditions are extremely crucial for microbial growth, enzymatic and cellular metabolic activities. Thus, the effects of different culture parameters like pH, temperature (degrees C), and agitation speed (RPM) on the indigenous Rhodococcus pyridinivorans strain PDB9T NS-1 were modeled using response surface methodology (RSM) and central composite design (CCD). The results showed that the main effect of pH and interaction between pH and agitation speed had a significant to a moderately significant effect on phenol degradation by the indigenous R. pyridinivorans strain PDB9T NS-1. Almost complete phenol degradation was obtained at an optimal setting of pH 7.5, 187 rpm, and 34 degrees C in 18 h. Growth and phenol degradation kinetics of the actinomycetes was examined in a batch shake flask under the optimized conditions. The growth of Rhodococcus species at varying initial levels of the phenol followed a Pamukoglu and Kargi substrate inhibition model with half-saturation constant (K-s) of 54.21 mg/l, maximum specific growth rate (mu(max)) of 0.169 (1/h), substrate inhibition constant (K-si) of 243.26 mg/l. The results obtained from the optimization of culture conditions and growth kinetics by the indigenous R. Pyridinivorans strain PDB9T NS-1 suggest the potential of the system in the treatment of phenolic wastewater.