Synergism of cellulase, pectinase and xylanase on hydrolyzing differently pretreated sweet potato residues.

The synergism of cellulase (C), pectinase (P), and xylanase (X) for the saccharification of sweet potato residues (SPR) was investigated. The removal of starch from SPR was easily achieved by using amylase, but the cellulose conversion of de-starched SPR was relatively low, thus dilute H₂SO₄, NaOH, and H₂O₂ pretreatment was conducted to improve the enzymatic digestibility. The lignin content of NaOH pretreated SPR was the lowest, whereas H₂SO₄ pretreatment resulted in the lowest contents of hemicellulose and pectin. The combination of C, P, and X exhibited different sugar production patterns, C-P displayed synergistic action on glucose and galactose production from each type of SPR, C-X also exhibited synergistic effect on glucose production except when H₂SO₄ pretreated SPR was used, whereas no synergism between P-X on monosaccharide production was observed. The presence of synergism between cellulase and mixed accessory enzymes [C-(PX)] on glucose formation was determined by C-X, and the degree of synergism between C-P and C-(PX) on glucose production had a positive relationship with pectin content. The highest cellulose conversion of 96.2% was obtained from NaOH pretreated SPR using mixed enzymes comprising C, P, and X with the ratio of 8:1:1.