Pathway identification, enzyme activity and kinetic study for the biodegradation of phenol by Nocardia hydrocarbonoxydans NCIM 2386

Abstract

Nocardia hydrocarbonoxydans NCIM 2386 (Nhy) can grow using phenol as a sole carbon source and has a strong ability to degrade phenol. The paper presents the main metabolism pathways and mechanism of phenol degradation by Nhy. Phenol was found to be degraded via meta cleavage of catechol by the action of enzyme catechol 2,3-dioxygenase. The enzyme was found to be both extracellular and cell bound. The cell bound and extracellular enzymes actively degraded phenol even in the absence of the organism. The rate of phenol degradation by extracellular enzymes as sole enzymatic process (in the absence of cells) was found to be almost similar to that with the whole cells, indicating the prominence of extracellular enzymes. Michaelis–Menten model was found to fit the degradation rate kinetics of total phenol for total phenol concentrations of less than 100 mg L−1 and also the degradation rate kinetics of catechol at catechol concentrations of less than 80 mg L−1 during the exponential growth phase of the organism. Michaelis– Menten model was found to fit the kinetics of catechol formation rate which is also equal to the actual rate of phenol degradation to catechol. Both phenol and catechol were found to be substrate inhibitory.