Enzymatic hydrolysis of dissolved corn stalk hemicelluloses: reaction kinetics and modeling

The enzymatic hydrolysis of hemicelluloses as a filtrate originating from aqueous/steam pretreated corn stalks was carried out using commercial enzyme systems of several activities composed of cellulases and beta-D-xylosidases from Aspergillus niger. The hydrolysis was conducted using free enzymes in aqueous substrate solution at a temperature of 30 C and a pH of 5. Saccharification corresponding to 90% of potential simple sugar release was obtained after 10 h using 0.12 activity units (U) of Cellulases 1 complex per mg of dissolved solids present in the filtrate. Synergetic action of Cellulases_1 enzyme complex and beta-D-xylosidases proved to be effective for the hydrolysis of plant hemicelluloses. A lumped model based on the Michaelis-Menten approach successfully described the fate of the lumped variables describing the hydrolysis of the overall kinetics of corn stalk hemicelluloses. The maximum saccharification rate evolved with the cellulases concentration as V-max(app) = K. [Cellulases](n). This overall and pseudokinetic tendency was comparable to those reported in the literature for more simple systems employing a defined substrate and a pure hydrolytic enzyme. The n-value was found to be in the range of 0.1-0.9 depending on the substrate lump involved in the reaction system. (C) 2003 Society of Chemical Industry.