Exploring chitosan-immobilized Rhizopus oligosporus lipase for olive-mill wastewater treatment

Wastewater released by olive mills is rich in lipids and oils which may have serious repercussions on the environment if left untreated, including soil deterioration, water contamination, and negative effects on aquatic life and its corresponding ecosystems. Thus, effective olive mill wastewater treatment is critical to remove oils and remediate such effluents for a sustainable environment. A lipolytic strain of Rhizopus oligosporus (Strain-3) was improved by developing L-Cysteine HCL resistance and harbored to gain maximum titers of lipases using submerged fermentation. Subsequently, the purified enzyme (Strain-3 and EM-4) was immobilized with chitosan beads after optimization studies. Finally, the effect of immobilized and free EM-4 Lipases was evaluated on olive mill wastewater treatment. During this study, the HCL-resistant EM-4 strain demonstrated maximum lipase production of 163 +/- 3.26 U/g under optimized conditions, outperforming the wild type. Furthermore, the optimized immobilization conditions for EM-4 lipases were determined to be 1 g of chitosan, 1 ml of enzyme concentration, and a 40-min procurement period at 40 degrees C. Nevertheless, 60% higher olive mill wastewater was degraded by immobilized lipases when 1 ml of wastewater was incubated for 10 min with the 5 U/ml diluted enzyme carried by chitosan beads. Immobilization of lipases using chitosan beads is a cost-effective and eco-friendly substitute for treating wastewater rich in lipids content.