Immobilization of polygalacturonase for the preparation of pectic oligosaccharides from mango peel wastes and assessment of their antibacterial activities

Abstract

In this study, we immobilized polygalacturonase by sol-gel entrapment for the continuous preparation of pectic oligosaccharides (POS) from mango peel wastes and evaluated their antibacterial activity. We characterized the immobilized polygalacturonase by scanning electron microscopy, thermo gravimetric analyzer, fourier transform infrared spectrometer and raman spectrum. Results showed that the polygalacturonase was successfully immobilized by the sol-gel encapsulation, which retained as much as 94.6% of its initial activity. The immobilized enzyme exhibited enhanced pH tolerance and thermal stability compared with its free counterpart. For example, the immobilized enzyme retained 57% of relative activity at 55 °C for 2 h, whereas the free enzyme retained only 17% of relative activity. Moreover, the immobilized enzyme showed good recyclability, which retained 65% of its initial activity after 6 batch reactions. Furthermore, we examined the antibacterial activities of POS prepared by the immobilized polygalacturonase hydrolysis by typical bacteria. The POS was mainly polygalacturonic acid formed by →1)-α-GalpA-(4→ and possessed the best antibacterial activity with a polymerization degree of 2–4. Therefore, we found it could be used as a natural antibacterial agent in food industry. These results suggested that immobilized polygalacturonase was efficient in terms of its high catalytic activity and stability, and it can be applied to continuous POS production.