Recyclable enzymatic recovery of pectin and punicalagin rich phenolics from waste pomegranate peels using magnetic nanobiocatalyst

Abstract

We demonstrate a novel recyclable enzymatic approach of extraction of pectin and punicalagin rich phenolics from the waste pomegranate peels (WPP) using the magnetic nanobiocatalyst technology. First, the cellulase was cross-linked with the iron oxide magnetic nanoparticles using glutaraldehyde to prepare the magnetic nanobiocatalyst which was characterized using FT-IR, FE-SEM, and TEM. Then, ultrasonically pre-treated WPP were hydrolyzed with the magnetic nanobiocatalyst at cellulase loading of 75 U/g of peel powder, pH 6 and 50 °C for 5 h to obtain maximum recovery of pectin (19.4%) and total phenolics (8.8%) comparable to non-green conventional methods. The magnetic nanobiocatalyst was easily recovered by the application of a magnetic field and recycled for five cycles with no change in pectin and total phenolics yields and cellulase activity. In addition, IR, 1H NMR, and TGA analysis showed that the chemical nature of pectin was the same in each cycle. The uronic acid content (72–74%), degree of esterification (62–64%), molecular weight (140–143 kDa) and polydispersity (1.5–1.6) of pectin from each cycle were also in the similar range. The total phenolics obtained in each cycle were rich in punicalagin (75–78% of total phenolics) with similar content of 6.42–6.65 g/100 g WPP. These results indicated the excellent stability and reusability of the cellulase magnetic nanobiocatalyst for the recovery of WPP pectin and phenolics of consistent yield and chemical nature/composition.