title: Effect and modeling of glucose inhibition and in situ glucose removal during enzymatic hydrolysis of pretreated wheat straw.
abstract: The enzymatic hydrolysis of lignocellulosic biomass is known to be product-inhibited by glucose. In this study, the effects on cellulolytic glucose yields of glucose inhibition and in situ glucose removal were examined and modeled during extended treatment of heat-pretreated wheat straw with the cellulolytic enzyme system, Celluclast 1.5 L, from Trichoderma reesei, supplemented with a beta-glucosidase, Novozym 188, from Aspergillus niger. Addition of glucose (0-40 g/L) significantly decreased the enzyme-catalyzed glucose formation rates and final glucose yields, in a dose-dependent manner, during 96 h of reaction. When glucose was removed by dialysis during the enzymatic hydrolysis, the cellulose conversion rates and glucose yields increased. In fact, with dialytic in situ glucose removal, the rate of enzyme-catalyzed glucose release during 48-72 h of reaction recovered from 20-40% to become approximately 70% of the rate recorded during 6-24 h of reaction. Although Michaelis-Menten kinetics do not suffice to model the kinetics of the complex multi-enzymatic degradation of cellulose, the data for the glucose inhibition were surprisingly well described by simple Michaelis-Menten inhibition models without great significance of the inhibition mechanism. Moreover, the experimental in situ removal of glucose could be simulated by a Michaelis-Menten inhibition model. The data provide an important base for design of novel reactors and operating regimes which include continuous product removal during enzymatic hydrolysis of lignocellulose.
authors.affiliation: Department of Chemical and Biochemical Engineering, Technical University of Denmark, Lyngby, Denmark.
authors.forename: Pavle
authors.initials: P
authors.lastname: Andrić
authors.forename: Anne S
authors.initials: AS
authors.lastname: Meyer
authors.forename: Peter A
authors.initials: PA
authors.lastname: Jensen
authors.forename: Kim
authors.initials: K
authors.lastname: Dam-Johansen
mesh_terms: D001234:Aspergillus niger / Q000201:enzymology; D055162:Biocatalysis / Q000187:drug effects; D002482:Cellulose / Q000378:metabolism; D004798:Enzymes / Q000378:metabolism*; D005947:Glucose / Q000302:isolation & purification* / Q000494:pharmacology*; D006868:Hydrolysis / Q000187:drug effects; D007700:Kinetics; D008956:Models, Chemical; D014242:Trichoderma / Q000201:enzymology; D014908:Triticum / Q000378:metabolism*
chemical_list: D004798:Enzymes; D002482:Cellulose; D005947:Glucose