Immobilized laccase of Galactomyces geotrichum on modified bentonite and its use in the bioremediation of olive mill wastewater†

Abstract

This work investigates the immobilization of laccase obtained from Galactomyces geotrichum onto modified bentonites. The structures of the composites were examined using SEM, FTIR, and BET techniques. Biocatalysts were evaluated in terms of activity, stability and kinetic parameters. Among the immobilized laccases, GDU-bent-lac exhibited the highest efficacy in operational (96% after 10 cycles), thermal (61% within 24 h at 65 °C), and storage (79.69% for 30 days) stabilities. Results suggested that the Langmuir model better correlated with the obtained data than the Freundlich isotherm. Results of the biodegradability study indicated that the increase in the biodegradability index of olive mill wastewater was remarkable when CTAB-bent-lac was used. Additionally, the bulk increase in the biodegradability was related to the support before laccase immobilization (0.43), and moreover, immobilization enhanced the biodegradability to some extent (0.46). In this research, a strong laccase-producing microorganism that was isolated from olive mill wastewater was used for the bioremediation of the same wastewater. To the best of our knowledge, the immobilization of laccase produced by G. geotrichum, isolated from OMW, onto modified bentonites has not been published earlier. Furthermore, the feasibility of using immobilized laccase to increase the biodegradability of OMW was investigated for the first time.