Degradation of Phenol by Immobilized Mycelium of Fusarium Flocciferum in Continuous Culture

Abstract

Continuous phenol degradation was studied in a completely mixed reactor, at steady state conditions, using the mycelium of Fusarium Floociferum immobilized in Polyurethane foam. Experiments at different dilution rates, 0.069, 0.118 and 0.196h−1 with an influent phenol concentration of 1g/l, showed a virtually complete substrate utilization over a period of four months. Low biomass productivity values of suspended cells were found, 0.21, 0.34 and 1.81g d.w./l. day, especially when compared with those obtained with the free cell system at similar conditions: 0.955 and 6.73g d.w./l.day for 0.063 and 0.116h dilution rates. The immobilized cells behaviour at different feed substrate concentrations was studied at D=0.196h.−1 corresponding to a retention time of 5.1h. The results indicate that above 1g/l the complete phenol removal is not achieved. A progressive increase in the outlet concentration was observed, attaining a value of 284mg/l at 1.5g/l. Respiratory experiments made with the immobilized cells taken from the reactor along with these experiment, indicate that the viability is retained by the mycelium, pointing out its ruling part in the phenol degradation. Culture fluid viscosity measurements were made and the rheological characteristics of the two systems were investigated. A non-Newtonian fluid was observed in the free cell system, with a shear-thinning behaviour. The immobilization had a beneficial effect on the rheology of the fluid i.e. the viscosity was much lower,1.2 c.p.s. and there was a tendency to approach Newtonian behaviour.