title: Activity modulation of core and shell in nanozeolite@enzyme bi-functional catalyst for dynamic kinetic resolution.
abstract: A core-shell nanozeolite@enzyme bi-functional catalyst is prepared by using nanozeolite β as acidic core and immobilized Candida antarctica lipase B (CALB) as enzyme shell for the purpose of dynamic kinetic resolution (DKR), and polydiallyldimethylammonium chloride (PDDA) is used as interlayer to compart core and shell. The activities of core and shell in bi-functional catalyst are modulated to achieve the matching between racemization and kinetic resolution (KR) rates in DKR, i.e., a slow racemization rate on core while a fast KR rate on shell. Nanozeolite β with intermediate SiO2/Al2O3 ratio provides proper acid amount for racemization step. A relatively thick layer of PDDA not only improves the activity of CALB by its coverage for surface acidic sites but also limits the accessibility and diffusion of substrate towards the acidic core. The CALB shell with larger immobilized amount and higher enzyme activity offers enhanced driving force of DKR process, leading to higher conversion, selectivity and yield. The preparation and activity modulation of core-shell catalyst provide an ideal method to improve the catalytic performance of bi-functional catalyst.
authors.affiliation: Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, Shanghai 200433, PR China.
authors.forename: Xiang
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, Shanghai 200433, PR China.
authors.forename: Yueer
authors.initials: Y
authors.lastname: Yan
authors.affiliation: Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, Shanghai 200433, PR China.
authors.forename: Wanlu
authors.initials: W
authors.lastname: Wang
authors.affiliation: Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, Shanghai 200433, PR China. Electronic address: zhangyh@fudan.edu.cn.
authors.forename: Yahong
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, Shanghai 200433, PR China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Tang
mesh_terms: D055162:Biocatalysis; D004798:Enzymes / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D008958:Models, Molecular; D053758:Nanoparticles / Q000737:chemistry*; D017641:Zeolites / Q000737:chemistry*
chemical_list: D004798:Enzymes; D017641:Zeolites
keywords: Activity modulation; Core–shell catalyst; Dynamic kinetic resolution (DKR); Enzyme immobilization; Nanozeolite