title: Enhanced biocatalytic esterification with lipase-immobilized chitosan/graphene oxide beads.
abstract: In this work, lipase from Candida rugosa was immobilized onto chitosan/graphene oxide beads. This was to provide an enzyme-immobilizing carrier with excellent enzyme immobilization activity for an enzyme group requiring hydrophilicity on the immobilizing carrier. In addition, this work involved a process for the preparation of an enzymatically active product insoluble in a reaction medium consisting of lauric acid and oleyl alcohol as reactants and hexane as a solvent. This product enabled the stability of the enzyme under the working conditions and allowed the enzyme to be readily isolated from the support. In particular, this meant that an enzymatic reaction could be stopped by the simple mechanical separation of the "insoluble" enzyme from the reaction medium. Chitosan was incorporated with graphene oxide because the latter was able to enhance the physical strength of the chitosan beads by its superior mechanical integrity and low thermal conductivity. The X-ray diffraction pattern showed that the graphene oxide was successfully embedded within the structure of the chitosan. Further, the lipase incorporation on the beads was confirmed by a thermo-gravimetric analysis. The lipase immobilization on the beads involved the functionalization with coupling agents, N-hydroxysulfosuccinimide sodium (NHS) and 1-ethyl-(3-dimethylaminopropyl) carbodiimide (EDC), and it possessed a high enzyme activity of 64 U. The overall esterification conversion of the prepared product was 78% at 60 °C, and it attained conversions of 98% and 88% with commercially available lipozyme and novozyme, respectively, under similar experimental conditions.
authors.affiliation: Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, Serdang, Selangor, Malaysia.
authors.forename: Siaw Cheng
authors.initials: SC
authors.lastname: Lau
authors.affiliation: Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, Serdang, Selangor, Malaysia; Institute of Advanced Technology, University Putra Malaysia, Serdang, Selangor, Malaysia.
authors.forename: Hong Ngee
authors.initials: HN
authors.lastname: Lim
authors.affiliation: Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, Serdang, Selangor, Malaysia; Laboratory of Molecular Biomedicine, Institute of Bioscience, Universiti Putra Malaysia, Serdang, Selangor, Malaysia.
authors.forename: Mahiran
authors.initials: M
authors.lastname: Basri
authors.affiliation: Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, Serdang, Selangor, Malaysia.
authors.forename: Hamid Reza
authors.initials: HR
authors.lastname: Fard Masoumi
authors.affiliation: Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, Serdang, Selangor, Malaysia.
authors.forename: Asilah
authors.initials: A
authors.lastname: Ahmad Tajudin
authors.affiliation: Low Dimensional Materials Research Centre, Department of Physics, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia.
authors.forename: Nay Ming
authors.initials: NM
authors.lastname: Huang
authors.affiliation: Low Dimensional Materials Research Centre, Department of Physics, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia.
authors.forename: Alagarsamy
authors.initials: A
authors.lastname: Pandikumar
authors.forename: Chin Hua
authors.initials: CH
authors.lastname: Chia
authors.affiliation: School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi, Selangor, Malaysia.
authors.forename: Chi Hua
authors.initials: CH
authors.lastname: Chia
authors.affiliation: Eco-Town Collaborative Research and Development Center for the Environment and Recycling, Kyushu Institute of Technology, Kitakyushu-shi, Fukuoka, Japan.
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Andou
mesh_terms: D055162:Biocatalysis; D019149:Bioreactors; D002175:Candida / Q000201:enzymology*; D048271:Chitosan / Q000737:chemistry; D004800:Enzymes, Immobilized / Q000378:metabolism*; D004951:Esterification / Q000502:physiology; D005233:Fatty Alcohols / Q000737:chemistry; D006108:Graphite / Q000737:chemistry; D006586:Hexanes / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D007850:Lauric Acids / Q000737:chemistry; D008049:Lipase / Q000378:metabolism*; D008855:Microscopy, Electron, Scanning; D008863:Microspheres; D014961:X-Ray Diffraction
chemical_list: D004800:Enzymes, Immobilized; D005233:Fatty Alcohols; D006586:Hexanes; D007850:Lauric Acids; C030358:lauric acid; C010268:oleyl alcohol; D006108:Graphite; D048271:Chitosan; D008049:Lipase