A highly acid-tolerant endoglucanase from Schizophyllum commune MA1 enables high-temperature saccharification of pretreated agricultural residues.

Fungi associated with basal stem rot-infected oil palm trees inhabit lignocellulose-rich environments and may provide robust cellulolytic enzymes. This study optimized endoglucanase production by Schizophyllum commune MA1, purified and characterized the enzyme, and preliminarily assessed a partially purified preparation against chemically pretreated agricultural residues. Taguchi screening followed by a central composite design within response surface methodology (RSM) increased carboxymethyl cellulase (CMCase) activity by 150%, from 0.60 to 1.50 U/mL. Ammonium sulfate precipitation and chromatographic purification yielded a 36.8-kDa endoglucanase with 24.4-fold purification and a specific activity of 1,181 U/mg. The purified enzyme showed maximal activity at pH 2.5 and 60 °C, retained full activity after 24 h at pH 2.5, and remained approximately 100% active at 50 °C for one month under the tested buffer conditions. The partially purified preparation hydrolyzed all tested residues; rice straw produced the highest reducing sugar concentration (1.95 g/L after 168 h), and scanning electron microscopy revealed marked fiber disruption after enzymatic treatment. This combination of strong acid activity, prolonged thermal stability, and biomass-hydrolyzing capability expands the known functional diversity of S. commune cellulases and provides proof-of-concept support for acidic, extended-duration lignocellulosic saccharification.