Raw oil palm frond leaves as cost-effective substrate for cellulase and xylanase productions by Trichoderma asperellum UC1 under solid-state fermentation

Abstract

Production of cellulases and xylanase by a novel Trichoderma asperellum UC1 (GenBank accession no. MF774876)under solid state fermentation (SSF)of raw oil palm frond leaves (OPFL)was optimized. Under optimum fermentation parameters (30 °C, 60–80% moisture content, 2.5 × 106 spores/g inoculum size)maximum CMCase, FPase, β-glucosidase and xylanase activity were recorded at 136.16 IU/g, 26.03 U/g, 130.09 IU/g and 255.01 U/g, respectively. Cellulases and xylanase were produced between a broad pH range of pH 6.0–12.0. The enzyme complex that comprised of four endo-β-1,4-xylanases and endoglucanases, alongside exoglucanase and β-glucosidase showed thermophilic and acidophilic characteristics at 50–60 °C and pH 3.0–4.0, respectively. Glucose (16.87 mg/g)and fructose (18.09 mg/g)were among the dominant sugar products from the in situ hydrolysis of OPFL, aside from cellobiose (105.92 mg/g)and xylose (1.08 mg/g). Thermal and pH stability tests revealed that enzymes CMCase, FPase, β-glucosidase and xylanase retained 50% residual activities for up to 15.18, 4.06, 17.47 and 15.16 h of incubation at 60 °C, as well as 64.59, 25.14, 68.59 and 19.20 h at pH 4.0, respectively. Based on the findings, it appeared that the unique polymeric structure of raw OPFL favored cellulases and xylanase productions.