Optimization of Nutrition Constituents for Xylanase Activity by Rhizopus stolonifer Under Solid-State Fermentation on Corncob

This study aims to optimize the medium for xylanase activity by a newly isolated strain of Rhizopus stolonifer JS-1008 (R. stolonifer JS-1008) under solid-state fermentation (SSF) on corncob. Four quantitative variables impacting the enzyme activity were selected through one-factor-at-a-time design. They were nitrogen source, initial moisture content (IMC), inorganic salt, and surface active agent. In addition, the interaction among these factors was further investigated by response surface methodology (RSM). Statistical analysis revealed that among these factors, IMC and urea significantly affected the xylanase activity. Our data indicate that the optimal medium contains (g/g dry corncob): urea, 0.15; ZnSO4, 0.022; Tween-80, 0.08; IMC, 3. Under the optimal condition, the xylanase activity reached its maximum, 13.90 U/g dry substrate (DS), on the 10th day of fermentation. This work provides a new potential strain to synthesize xylanase for biofuel production.