Sustainable Nepenthes mirabilis facilitated recovery of reducing sugars from grape pomace

Abstract

Grape pomace (GP) generated from the winery industry is one of the abundant agro-waste in the Western Cape, South Africa and other regions globally. GP contains a significant quantity of holocelluloses that can be converted into fermentable total reducing sugars (TRS). This study reports on the recovery of TRS from GP treated Nepenthes mirabilis digestive fluids for mediated biovalorisation in comparison to a combination of conventional pretreatment methods (hot water pretreatment, dilute acid pretreatment, and cellulase pretreatment) in a single pot system. The recovery of TRS was facilitated while also reducing total residual phenolics (TRPCs) in the samples. Furthermore, powder X-ray diffraction (pXRD) was used to measure the crystallinity index and the functional groups of pre- and post-pre-treated GP were determined using Fourier-transform infrared spectroscopy (FTIR) to ascertain the efficiency of the pretreatment methods, with quantification of lignin, holocellulose and ash being conducted. Overall, the TRS yield for N. mirabilis pre-treated agrowaste was 951±4.7 mg/L, with biomass having a lower CrI of 33%, and 62% residual lignin content. Furthermore, reduced TRPCs were observed in hydrolysate, suggesting limited inhibitory by-product formation during N. mirabilis pre-treatment.