Valorization of Goruba (Hyphaene thebaica L) Fruit Waste for Optimized Prebiotic Xylooligosaccharides Production via Aspergillus flavus Xylanase

Abstract

Goruba (Hyphaene thebaica) fruit waste is an underutilized, xylan-rich residue that can be enzymatically converted into xylooligosaccharides (XOS). XOS are non-digestible prebiotic oligosaccharides that function as soluble dietary fiber by supporting beneficial gut microbes. The aim of this research was to valorize ‘Goruba’ (Hyphaene thebaica) fruit waste for XOS production. Xylan was obtained from ‘Goruba’ sample using alkaline extraction. Aspergillus flavus was used to synthesize xylanase enzyme from xylan medium under solid state fermentation (SSF) and the xylanase was assayed using DNS method. Hydrolysis of xylan to XOS was carried using the fungal xylanase. Produced XOS was analyzed using HPLC. Production of XOS was optimized using Response Surface Method (RSM) approach. One way ANOVA (p < 0.05), mean ± SD and numerical optimization were adopted to analyze the data. Highest xylan yield was 34.35±1.02% with 9.0% NaOH. Total protein in the crude extract was 362.3 mg with total activity 2,829 U and specific activity 7.81 U/mg. Xylanase activity peaked at 22.33 U/mL at 50 °C, pH 6.0. The HPLC fractions (mg/mL) were xylose 2.43, xylobiose 8.65, xylotriose 5.22, xylotetraose 2.75, xylopentaose 1.03, xylohexaose 0.81, and DP > 6 = 4.03, totaling 24.92 mg/mL. Ammonium sulphate precipitation gave protein (41.17 mg), total activity (2737 U), specific activity (66.48U/mg) and 96.74% yield. Numerical optimized XOS was 26.05 mg/mL at 52℃, pH (7.90), at 2 hours, enzyme dose (2 U/mL) and substrate dose (8.50 mg/mL). This study has established that the ‘Goruba’ fruit waste is a good source of prebiotics-XOS and can be used for large-scale production due to its affordability and availability.