Effect of submerged culture conditions on the degradation of pentachlorophenol by Rhizopus nigricans

The objective of this work was to determine the submerged culture conditions required to obtain the optimal efficiency of degradation of pentachlorophenol by Rhizopus nigricans. Growth and pentachlorophenol degradation kinetics were determined using varied C/N ratios and shaking speeds. Cultures were carried out using Melin-Norkrans medium, with conditions determined by means of a factorial design. It was demonstrated that acting alone, temperature did not influence the degradative capacity of Rhizopus nigricans, while the C/N ratio, pH and degree of agitation had significant effects. The best efficiency for pentachlorophenol degradation was achieved with a C/N ratio of 18.9, initial pH of 5.5, temperature of 30 °C, and agitation velocity of 125 rpm. Under these conditions the efficiency of degradation was raised from 0.018 to 0.028 mg PCF biomass ^-1 h^-1, suggesting that it may be possible to utilize Rhizopus nigricans in the degradation of chlorophenols.