Abstract
Laccase from Trametes Versicolor was successfully immobilized on gelatin beads by a crosslinking reaction with glutaraldehyde. Immobilized laccases showed better stability towards pH and temperature than free laccases. Moreover, the immobilized laccases retained a good relative activity of 85% after 20 days of storage at 4°C. The degradation of tetracycline (TC) was studied with immobilized enzymes in both batch and fluidized bed reactors (FBR). The average degradation rate (1.59 mg h$^{-1}$ Uenzymes$^{-1}$) estimated over 24 hours in the FBR was almost 5 times higher than in the stirred tank reactor. Maximum degradation rate achieved was 72 ± 1% with a circulation flow rate of 80 mL min$^{-1}$ and addition of air at a flowrate of 15 mL min$^{-1}$. Study of the stability of the active beads under reaction conditions, shows that 45% of the TC was degraded after 5 cycles of 24 hours each. The toxicity of the TC solution before and after treatment was also investigated with microtox assays.