Microwave-assisted covalent immobilization of enzymes on inorganic surfaces

Enzymes on carriers can be easily recycled or used in fixed bed reactors. The immobilization often results in an improved stability. Depending on the support used and the method of coupling, this is a time-consuming process. While the wide applicability of microwaves (MWs) within organic synthesis is known since the 1980s, proteins (including enzymes) are generally considered as too sensitive toward MW irradiation. In this article, MW methods were investigated to improve the processing speed of covalent enzyme immobilization on inorganic supports. Herein two laccases from Trametes versicolor and Myceliophthora thermophilia (Novozyme 51003 (R)) and the glucose oxidase from Aspergillus niger were immobilized onto samples of ceramic honeycomb and porous glass (TRISOPERL (R) 1000 AMINO). The enzymes showed different sensitivity to MW irradiation, but all were suitable for MW-assisted immobilization. Subsequent stability tests were conducted to compare conventional immobilization methods with those with MW irradiation. The glucose oxidase provided the best results. For all cases, a successful MW irradiation assisted covalent enzyme immobilization on solid support was obtained with a total 20-fold reduction of the time necessary.