Solid-state valorization of raw oil palm leaves by novel fungi Trichoderma asperellum UC1 and Rhizopus oryzae UC2 for sustainable production of cellulase and xylanase

Abstract

BACKGROUND: The growing demand for cellulases and xylanases in lignocellulosic degradation and reutilization has spurred the need for their improved production at reduced cost. Abundantly available oil palm leaves (OPL) promise an alternative and sustainable substrate for producing such enzymes in the degradation and biotransformation of unwanted lignocellulosic biomass. Both enzymes are key players in the transformation of biomass into other value-added commodities. RESULTS: This study statistically optimized the solid-state fermentation (SSF) of raw OPL by novel fungal strains Trichoderma asperellum UC1 and Rhizopus oryzae UC2, to produce cellulase and xylanase, where raw OPL was pretreated using ultrasonication before the dual enzyme-assisted saccharification process. This experiment aimed to identify the best parameters for the highest activity of CMCase (EC 3.2.1.4), FPase (EC 3.2.1.91) and xylanase (EC 3.2.1.8) of T. asperellum UC1 and of β-glucosidase (EC 3.2.1.21) of R. oryzae UC2 for improved saccharification. Activities of CMCase (126.87 U g−1), FPase (85.53 U g−1) and xylanase (215.42 U g−1) achieved the maximum under optimized SSF conditions (30 °C, 2.0 × 107 spores g−1, 75% moisture content, pH 6). The best β-glucosidase activity (131.76 U g−1) was obtained at 32 °C, 2.0 × 107 spores g−1, 50% moisture content, pH 12. OPL saccharification yielded 1240 ± 32 mg g−1 total reducing sugar. Individual enzyme cocktails improved juice clarification (84–88%) and dough rising (1.7- to 2.0-fold). CONCLUSIONS: The optimized SSF of raw OPL successfully afforded the production of effective cellulases and xylanases for saccharification-related reactions. © 2021 Society of Chemical Industry (SCI).