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- Optimization in the immobilization of penicillin G acylase by entrapment in xerogel particles with magnetic propertiesPublication . Bernardino, Susana; Estrela, Nídia; Ochoa-Mendes, Vanessa; Fernandes, Pedro; Fonseca, Luís P.Biocatalysis presents a sound alternative to chemical synthesis in the field of drug production, given the highly selective nature of biological catalysts. Penicillin G Acylase (PGA) from E. coli is currently used to hydrolyze penicillin G (PG) and catalyzes the synthesis of β-lactam antibiotics. In this work, particular emphasis is given to recent developments in penicillin G acylase immobilization, by entrapment simultaneously with nano-magnetic particles in a silica matrix. The sol-gel biocatalytic particles were prepared either by a conventional method (crushed powder) or by a more recent approach, based in an emulsion system using 150 mM AOT/isooctane, which allowed for the formation of spherical micro- and nanobeads. The effects on PGA activity of different sol-gel precursors, additives, enzyme concentration, aging, drying conditions and mechanical stability were evaluated. After these optimization studies, a mechanically stable carrier based on porous xerogels silica matrixes, starting from tetramethoxysilane (TMOS) with 65-67% PGA activity yield in these carriers allowed an immobilization yield of 74 mg protein g dry sol-gel -1 and 930 Ug dry sol-gel -1 for specific activity were obtained.