Upgrading the fermentability and prebiotic potential of palm decanter cake through fibre-degrading enzymatic treatments

Abstract

Palm oil milling has produced tonnes of solid waste including palm decanter cake (PDC). The recalcitrant nature of PDC limits its full inclusion in animal feed. This study aims to investigate the effect of fibre-degrading enzyme such as cellulase and xylanase on the prebiotic activity and solid state fermentability of PDC. We used the following commercial enzyme loading: 5U cellulase (5UC), 5U xylanase (5UX) and combined enzymatic treatment 2.5U:2.5U (C25U) per gram of substrate to hydrolyse the defatted PDC. The sugar profile in the effluent was analysed by using high-performance liquid chromatography, and the degree of hydrolysis (DH) was estimated based on the total carbohydrates amount in the effluent. The DH of enzymatic-hydrolysed PDC followed the order of 5UC< C25U <5UX, which was 7.8 %, 44.2 2% and 46.27 %, respectively. The prebiotic activity score of ethanolic extract obtained from the PDC followed the order of untreated < C25U < 5UX < 5UC, which were -1.04, -0.74, -0.10 and 0.58, respectively. To further investigate the role of lignin (which can be eliminated through alkaline hydrogen peroxide treatment (AHPT) on the extent of hydrolysis and the fermentability of enzymatic-hydrolysed PDC, we tested the invasion capacity of fungus Aspergillus oryzae on untreated, and AHPT followed by enzymatic-treated PDC. Pre-treatment of PDC with AHP improved accessibility for enzymatic hydrolysis in which the highest fungus growth rate was observed on the AHP-C25U PDC. Enzymatic treatment succeeding AHPT is a feasible way to improve the fermentability of palm decanter cake.