title: Glucoamylase immobilization on a magnetic microparticle for the continuous hydrolysis of maltodextrin in a fluidized bed reactor.
abstract: Glucoamylase (GA) has been successfully immobilized through its carbohydrates previously oxidized with periodate onto a low-cost magnetic microparticle made of polyethyleneimine-coated magnetite crosslinked with glutaraldehyde (M-GAD) and derivatized with adipic dihydrazide (ADH). A stabilization posttreatment consisting of crosslinking its carbohydrates with ADH, increased the remaining activity from 54 to 71%, calculated on the Vm values and measured at 50 degrees C and pH 4.5 with maltodextrin (DE 11-14) as substrate. This treatment also improved the enzyme stability and lowered the deactivation rate constant kd to a third of its value. A 30% maltodextrin solution has been continuously hydrolyzed at 50 degrees C and pH 4.5 in a recycled, fluidized bed reactor (FBR) containing GA immobilized on these magnetic microparticles. They easily settled in this highly viscous medium because of their high density (5 g/mL), and washout of ultrafines was prevented by surrounding the top of the bed with an electromagnet. The small particle size (20 microns) allowed a high enzyme loading in the reactor and also a high bed voidage, which is recommended to avoid extensive pressure drop and consequent channeling problems. The kinetic of hydrolysis fitted with the plug-flow model; this is explained by the insignificant backmixing effects observed. After 2 wk of hydrolysis under process conditions leading to a conversion of 70%, which corresponds to a high-conversion syrup, the immobilized GA only lost 4% of its initial activity.
authors.affiliation: Laboratoire de Génie Enzymatique, UMR 106 CNRS, Université Claude Bernard-Lyon 1, Villeurbanne, France.
authors.forename: B R
authors.initials: BR
authors.lastname: Pieters
authors.forename: G
authors.initials: G
authors.lastname: Bardeletti
authors.forename: P R
authors.initials: PR
authors.lastname: Coulet
mesh_terms: D015374:Biosensing Techniques; D003432:Cross-Linking Reagents; D004800:Enzymes, Immobilized; D005087:Glucan 1,4-alpha-Glucosidase / Q000737:chemistry*; D005947:Glucose / Q000032:analysis; D006868:Hydrolysis; D007700:Kinetics; D008280:Magnetics; D008433:Mathematics; D008863:Microspheres; D008962:Models, Theoretical; D010084:Oxidation-Reduction; D011134:Polysaccharides / Q000737:chemistry*; D013997:Time Factors
chemical_list: D003432:Cross-Linking Reagents; D004800:Enzymes, Immobilized; D011134:Polysaccharides; C008315:maltodextrin; D005087:Glucan 1,4-alpha-Glucosidase; D005947:Glucose