Optimization and Kinetic Evaluation of Acetylxylan Esterase and Xylanase Production by Trichoderma reesei Using Corn Cob Xylan

Performance of Trichoderma reesei in the production of acetylxylan esterase (AXE) and xylanase (Xyl(using corn cob xylan as the growth substrate was evaluated. The FT-IR findings confirmed purity of the xylan extracted by use of sonication method. Michaelis-Menten equation was used to describe the kinetic behavior of the enzymes while the fungus growth was modeled using logistic equation. The maximum biomass production was 2.34 g L-1 and the half-saturation constants for Xyl and AXE were 2.03 and 0.77 mg mL(-1), respectively. Effects of some environmental factors, including xylan concentration, cell population and pH on the enzymes production were quantified considering the response surface methodology (RSM) concept. The influential parameters were optimized by central composite design (CCD) and further analysis and model validation was done. Under optimized condition, maximum AXE and Xyl activity was observed at 1.55 and 11.08 U mL(-1), which was almost the same as predicted values. Trends of the enzymes production were also monitored in a packed-bed reactor using kissiris pieces for fungus immobilization. Under immobilized condition, Xyl activity was found 1.5 times higher than that produced under free cells, while no noticeable difference was observed in AXE production by immobilized cells due to the diffusional limitations.