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Enhanced Synthesis of Alkyl Galactopyranoside by Thermotoga naphthophila β‑Galactosidase Catalyzed Transglycosylation: Kinetic Insight of a Functionalized Ionic Liquid-Mediated System

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journal contribution
posted on 11.01.2017, 00:00 by Jingwen Yang, Bianca Pérez, Sampson Anankanbil, Jingbo Li, Renjun Gao, Zheng Guo
Green synthesis is of pivotal importance for environmental sustainability. This work reports a novel approach to synthesize an array of alkyl galactopyranosides using thermophilic β-galactosidase from Thermotoga naphthophila RKU-10 (TN1577) as biocatalyst and milk processing waste lactose as galactosyl donor. Ammoeng 102 (only 2.5% addition of total reaction volume), a functionalized ionic liquid (IL) containing tetraaminum cation with C18 acyl and oligoethylene glycol, is identified as the most promising one from a variety of structurally diverse ILs, affording a 2.37-fold increase in octyl galactopyranoside yield compared to the buffer system. Up to 18.2 g L–1 octyl galactopyranoside could be produced in 7 h, which is significantly higher than any previous report in terms of time-space efficiency. Kinetic study and COSMO-RS in silico predictions elucidate that the thermophilic nature of TN1577 β-galactosidase, increased solubility of substrate, suppression of hydrolysis, and excellent biocompatibility of Ammoeng 102 with enzyme (allowing TN1577 β-galactosidase to perform optimal catalysis up to 95 °C) are the main driving forces. The general applicability of the Ammoeng 102 system is verified, by which a series of alkyl galactopyranosides are successfully synthesized with n-butanol to n-tetradecanol as alkyl acceptors and lactose as galactosyl donor.