Abstract
Epoxides of vegetable oils and free and methylated fatty acids are of interest for several industrial applications. In the present work, refined rapeseed, sunflower, soybean, and linseed oils, with very different profiles of mono- and poly-unsaturated fatty acids, were saponified and transesterified, and the products treated with wild unspecific peroxygenases (UPOs, EC 1.11.2.1) from the ascomycete Chaetomium globosum (CglUPO) and the basidiomycete Marasmius rotula (MroUPO), as well as with recombinant UPO of the ascomycete Humicola insolens (rHinUPO), as an alternative to chemical epoxidation that is non-selective and requires strongly acidic conditions. The three enzymes were able of converting the free fatty acids and the methyl esters from the oils into epoxide derivatives, although significant differences in the oxygenation selectivities were observed between them. While CglUPO selectively produced “pure” epoxides (monoepoxides and/or diepoxides), MroUPO formed also hydroxylated derivatives of these epoxides, especially in the case of the oil hydrolyzates. Hydroxylated derivatives of non-epoxidized unsaturated fatty acids were practically absent in all cases, due to the preference of the three UPOs selected for this study to form the epoxides. Moreover, rHinUPO, in addition to forming monoepoxides and diepoxides of oleic and linoleic acid (and their methyl esters), respectively, like the other two UPOs, was capable of yielding the triepoxides of α-linolenic acid and its methyl ester. These enzymes appear as promising biocatalysts for the environmentally friendly production of reactive fatty-acid epoxides given their self-sufficient monooxygenase activity with selectivity toward epoxidation, and the ability to epoxidize, not only isolated pure fatty acids, but also complex mixtures from oil hydrolysis or transesterification containing different combinations of unsaturated (and saturated) fatty acids.
Highlights
In the search for sustainable chemistry, considerable attention is being paid to renewable feedstocks and, among these, vegetable oils represent a great proportion of the current consumption by the chemical industry
MroUPO and CglUPO are wild enzymes isolated at JenaBios (Jena, Germany) from pure cultures of M. rotula DSM 25031 and C. globosum DSM 62110 from the German Collection of Microorganisms and Cell Cultures (Braunschweig, Germany). rHinUPO is a recombinant enzyme obtained at Novozymes A/S (Bagsvaerd, Denmark) (Kiebist et al, 2017), by heterologous expression of the cloned gene in the A. oryzae industrial host, using proprietary technology (Landvick et al, 2016)
With the aim of achieving an accurate quantification of fatty acids in triglycerides, saponification and transesterification of vegetable oils were performed, and the fatty-acid and fatty-acid methyl esters (FAMEs) patterns were analyzed by GC-MS
Summary
In the search for sustainable chemistry, considerable attention is being paid to renewable feedstocks and, among these, vegetable oils represent a great proportion of the current consumption by the chemical industry. Most of oleochemical reactions have been those occurring at the Biobased Epoxides by Fungal Peroxygenases fatty acid carboxy group, while only a very minor proportion of them have involved transformations of the alkyl chain. The latter reactions have great potential for extending the range of compounds available from oils and fats. By simple industrial procedures, fatty acids are available from vegetable oils in such purity that they may be used for further chemical transformations Their conversion to fatty-acid methyl esters (FAMEs) is a well-known application, largely investigated for biodiesel production. Unsaturated fatty acids and FAMEs can be further epoxidized, and used in industrial syntheses of chemicals and intermediates
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