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

Abstract

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 (°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 °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 (µ_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.

Keywords:

• Biokinetic parameters
• culture condition
• central composite design
• phenol
• Rhodococcus pyridinivorans PDB9T NS-1
• substrate inhibition kinetic

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The authors acknowledge the financial support received from the Government of India Ministry of Science and Technology Department of Biotechnology [File No. BT/PR15242/BCE/8/1144/2015 and the Science and Engineering Research Board (SERB) (a statutory body of the Department of Science and Technology, Government of India) [File No. YSS/201S/000984] for carrying out this research work.