title: Lipase-catalyzed synthesis of ascorbyl oleate in acetone: optimization of reaction conditions and lipase reusability.
abstract: Lipase-catalyzed ascorbyl oleate synthesis is eco-friendly and selective way of production of liposoluble biocompatible antioxidants, but still not present on an industrial level due to the high biocatalyst costs. In this study, response surface methodology was applied in order to estimate influence of individual experimental factors, identify interactions among them, and to determine optimum conditions for enzymatic synthesis of ascorbyl oleate in acetone, in terms of limiting substrate conversion, product yield, and yield per mass of consumed enzyme. As a biocatalyst, commercial immobilized preparation of lipase B from Candida antarctica, Novozym 435, was used. In order to develop cost-effective process, at reaction conditions at which maximum amount of product per mass of biocatalyst was produced (60°C, 0.018 % (v/v) of water, 0.135 M of vitamin C, substrates molar ratio 1:8, and 0.2 % (w/v) of lipase), possibilities for further increase of ester yield were investigated. Addition of molecular sieves at 4(th) hour of reaction enabled increase of yield from 16.7 mmol g⁻¹ to 19.3 mmol g⁻¹. Operational stability study revealed that after ten reaction cycles enzyme retained 48 % of its initial activity. Optimized synthesis with well-timed molecular sieves addition and repeated use of lipase provided production of 153 mmol per gram of enzyme. Further improvement of productivity was achieved using procedure for the enzyme reactivation.
authors.affiliation: Department of Biochemical Engineering and Biotechnology, Faculty of Technology and Metallurgy, University of Belgrade, Belgrade, Serbia.
authors.forename: Marija
authors.initials: M
authors.lastname: Stojanović
authors.forename: Dušan
authors.initials: D
authors.lastname: Velićković
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Dimitrijević
authors.forename: Nenad
authors.initials: N
authors.lastname: Milosavić
authors.forename: Zorica
authors.initials: Z
authors.lastname: Knežević-Jugović
authors.forename: Dejan
authors.initials: D
authors.lastname: Bezbradica
mesh_terms: D000096:Acetone / Q000737:chemistry*; D000975:Antioxidants / Q000138:chemical synthesis* / Q000378:metabolism; D001205:Ascorbic Acid / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000138:chemical synthesis; D055162:Biocatalysis; D001671:Biochemistry / Q000379:methods*; D001672:Biocompatible Materials / Q000138:chemical synthesis* / Q000378:metabolism; D002175:Candida / Q000201:enzymology; D005656:Fungal Proteins / Q000378:metabolism*; D008049:Lipase / Q000378:metabolism*; D009829:Oleic Acids / Q000096:biosynthesis / Q000138:chemical synthesis*; D013997:Time Factors; D014867:Water
chemical_list: D000975:Antioxidants; D001672:Biocompatible Materials; D005656:Fungal Proteins; D009829:Oleic Acids; D014867:Water; D000096:Acetone; D008049:Lipase; C431349:lipase B, Candida antarctica; D001205:Ascorbic Acid; C502797:ascorbyl oleate