title: Dendrimer-like nanoparticles based β-galactosidase assembly for enhancing its selectivity toward transgalactosylation.
abstract: Functional nanomaterials have been pursued to assemble nanobiocatalysts since they can provide unique hierarchical nanostructures and localized nanoenvironments for enhancing enzyme specificity, stability and selectivity. Functionalized dendrimer-like hierarchically porous silica nanoparticles (HPSNs) was fabricated for assembling β-galactosidase nanobiocatalysts for bioconversion of lactose to galacto-oligosaccharides (GOS). The nanocarrier was functionalized with amino (NH2) and carboxyl (COOH) groups to facilitate enzyme binding, benchmarking with non-functionalized HPSNs. Successful conjugation of the functional groups was confirmed by FTIR, TGA and zeta potential analysis. HPSNs-NH2 showed 1.8-fold and 1.1-fold higher β-galactosidase adsorption than HPSNs-COOH and HPSNs carriers, respectively, with the highest enzyme adsorption capacity of 328mg/g nanocarrier at an initial enzyme concentration of 8mg/ml. The HPSNs-NH2 and β-galactosidase assembly (HPSNs-NH2-Gal) demonstrated to maintain the highest activity at all tested enzyme concentrations and exhibited activity up to 10 continuous cycles. Importantly, HPSNs-NH2-Gal was simply recycled through centrifugation, overcoming the challenging problems of separating the nanocarrier from the reaction medium. HPSNs-NH2-Gal had distinguished catalytic reaction profiles by favoring transgalactosylation, enhancing GOS production of up to 122g/l in comparison with 56g/l by free β-galactosidase. Furthermore, it generated up to 46g/l GOS at a lower initial lactose concentration while the free counterpart had negligible GOS production as hydrolysis was overwhelmingly dominant in the reaction system. Our research findings show the amino-functionalized HPSNs can selectively promote the enzyme activity of β-galactosidase for transgalactosylation, which is beneficial for GOS production.
authors.affiliation: School of Chemical Engineering, The University of Adelaide, Adelaide, SA 5000, Australia; Biotechnology Research Institute, Universiti Malaysia Sabah, Jalan UMS, 88400 Kota Kinabalu, Sabah, Malaysia.
authors.forename: Mailin
authors.initials: M
authors.lastname: Misson
authors.affiliation: Research Center for Bioengineering and Sensing Technology, University of Science & Technology Beijing, Beijing100083, PR China.
authors.forename: Xin
authors.initials: X
authors.lastname: Du
authors.affiliation: School of Chemical Engineering, The University of Adelaide, Adelaide, SA 5000, Australia.
authors.forename: Bo
authors.initials: B
authors.lastname: Jin
authors.affiliation: School of Chemical Engineering, The University of Adelaide, Adelaide, SA 5000, Australia. Electronic address: hu.zhang@adelaide.edu.au.
authors.forename: Hu
authors.initials: H
authors.lastname: Zhang
mesh_terms: D055162:Biocatalysis; D050091:Dendrimers / Q000737:chemistry; D004800:Enzymes, Immobilized / Q000378:metabolism; D006031:Glycosylation; D007785:Lactose / Q000378:metabolism; D008855:Microscopy, Electron, Scanning; D053758:Nanoparticles / Q000737:chemistry / Q000648:ultrastructure; D009844:Oligosaccharides / Q000096:biosynthesis; D016062:Porosity; D012822:Silicon Dioxide; D001616:beta-Galactosidase / Q000378:metabolism*
chemical_list: D050091:Dendrimers; D004800:Enzymes, Immobilized; D009844:Oligosaccharides; D012822:Silicon Dioxide; D001616:beta-Galactosidase; D007785:Lactose
keywords: Dendrimer-like hierarchical pores silica nanoparticles; Galacto-oligosaccharides; Nanobiocatalysis; β-Galactosidase