title: Enhancement of microwave-assisted covalent immobilization of penicillin acylase using macromolecular crowding and glycine quenching.
abstract: In order to create macromolecular crowding resembling cells in mesopores and improve the covalent immobilization of penicillin acylase (PA), macromolecular reagents were covalently assembled on the walls of mesocellular silica foams (MCFs) and paralleled enzyme molecules under microwave irradiation at low temperatures. The effects of kind and content of macromolecules on immobilization and the characteristics of the immobilized enzyme were investigated carefully. The maximum specific activities of PA assembled with Dex 10 (Dextran, Mw 10000) (85.3 U/mg) and BSA (Bovine Serum Albumin) (112.7 U/mg) in MCFs under microwave irradiation were 1.73 and 1.31 times, respectively, that of PA solely immobilized by the conventional method. The optimum reaction temperature rose from 45-55 degrees C. Moreover, amino acids were used to quench excess activated groups in order to improve the thermostability of the immobilized enzyme. PA coassembled with Dex 10 in mesopores retained 88% of its initial catalytic activity after heating at 50 degrees C for 6 h, as a result of glycine quenching the excess activated groups. This biomolecule enhanced the thermostability of the enzyme preparation by 2-fold. A crowding environment resembling cells made from macromolecular reagents would be suitable for stabilizing the structure of PA and improving its catalytic activity. Glycine, a small biocompatible molecule, quenched the excess activated groups and modified the surface chemical properties of the mesoporous support, which would further favor the stability of PA at higher temperatures. Combining macromolecular crowding with glycine quenching was one of the efficient strategies adopted to improve microwave-assisted covalent PA immobilization.
authors.affiliation: National Engineering Research Center for Biotechnology, Nanjing 210009, PR China.
authors.forename: Anming
authors.initials: A
authors.lastname: Wang
authors.forename: Cheng
authors.initials: C
authors.lastname: Zhou
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Du
authors.forename: Mingqing
authors.initials: M
authors.lastname: Liu
authors.forename: Shemin
authors.initials: S
authors.lastname: Zhu
authors.forename: Shubao
authors.initials: S
authors.lastname: Shen
authors.forename: Pingkai
authors.initials: P
authors.lastname: Ouyang
mesh_terms: D001407:Bacillus / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D003911:Dextrans / Q000737:chemistry; D004800:Enzymes, Immobilized; D005998:Glycine / Q000378:metabolism*; D046911:Macromolecular Substances / Q000737:chemistry / Q000378:metabolism; D008872:Microwaves; D010399:Penicillin Amidase / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D012710:Serum Albumin, Bovine / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D013379:Substrate Specificity; D013696:Temperature
chemical_list: D001426:Bacterial Proteins; D003911:Dextrans; D004800:Enzymes, Immobilized; D046911:Macromolecular Substances; D012710:Serum Albumin, Bovine; D012822:Silicon Dioxide; D010399:Penicillin Amidase; D005998:Glycine