# Enhancing the Stability of Fungal Lipases by Immobilization onto Accurel MP 1000 Support and Additional Glutaraldehyde Crosslinking

## TL;DR

This study shows that immobilizing fungal lipases on a polypropylene support and using glutaraldehyde crosslinking significantly improves their stability and reusability in different conditions.

## Contribution

The novel contribution is the systematic evaluation of glutaraldehyde crosslinking's effect on immobilized fungal lipases' stability and performance.

## Key findings

- Immobilized lipases retained over 50% activity for 3–10 cycles, with glutaraldehyde enhancing reusability.
- Immobilized enzymes preserved 50–100% activity during storage, unlike soluble enzymes which lost most activity.
- Immobilization improved thermal and pH stability, with hexane showing the highest solvent tolerance.

## Abstract

Commercial fungal lipases from Rhizopus oryzae, Rhizopus niveus, Aspergillus niger, Rhizomucor miehei, and Candida rugosa were immobilized via physical adsorption onto Accurel MP 1000, a hydrophobic polypropylene support. The effects of enzyme concentration, pH, temperature, and glutaraldehyde post-treatment were systematically evaluated. Immobilization generally enhanced enzyme stability, which was further improved in several cases by glutaraldehyde crosslinking. The immobilized preparations retained over 50% of their initial activity for 3–6 cycles, and 7–10 cycles following glutaraldehyde treatment. While soluble enzymes lost nearly all activity within three months at 5 °C and 25 °C and retained only 5–20% at −20 °C, the immobilized forms preserved 50–100% of their activity under all storage conditions tested. Immobilized lipases also exhibited improved thermal stability at 60 °C by general increments between 1.3 and 1.8 times compared to soluble lipases. Increased tolerance to pH fluctuations was observed in most immobilized enzymes, particularly from R. oryzae, R. niveus, R. miehei, and C. rugosa. Organic solvent tolerance of the immobilized enzymes showed highest stability in hexane (66–100% residual activity after 4 h incubation). Glutaraldehyde treatment affected solvent stability of immobilized lipases in enzyme and solvent dependent manner. These findings demonstrate the improved stability and applicability of the produced biocatalysts in varying reaction environments.