Preparation of triglyceride and fatty acid epoxides

Application and production of plant epoxides

The epoxidation of unsaturated fatty acids and triglycerides produces products with increased polarity and reactivity. Vegetable oil-based epoxides are mostly chemically produced on an industrial scale from soy oil. They can be used as PVC stabilizers, plasticizers, for the synthesis of biobased resins and coatings or, after further conversion, as components of lubricant formulations. Epoxidation takes place via the so-called Prileschajew reaction, in which olefinic double bonds of the unsaturated fatty acids are converted to epoxy (oxirane) by peracid. Peracid formation often occurs in situ by reaction of hydrogen peroxide with acetic or formic acid using strong mineral acids, for example sulfuric acid, or ion exchange resins as catalyst. In the chemical conversion process control is particularly problematic due to a strongly exothermic reaction, strongly acidic reaction conditions and associated side reactions as well as high salt production during product processing.

An alternative to this chemical process is chemo-enzymatic epoxidation, in which a lipase enzymatically catalyses the formation of peracid from fatty acid and hydrogen peroxide. The main advantages are milder process conditions and greater selectivity in implementation. Undesirable ring opening reactions occurring in the chemical method can be avoided as far as possible in the chemo-enzymatic process.

Fraunhofer IGB is investigating the oleochemical use of oils and fats in various projects and is also focusing on the enzymatic production of epoxy building blocks for various fields of application. The focus is on the one hand on the identification of suitable biocatalysts and on the other hand on process development and scaling of the multiphase reaction system together with the Fraunhofer CBP in Leuna. When selecting the renewable raw materials used, particular importance is attached to using non-food-relevant substrates.

New enzymes for peracid formation

In a screening, new, non-commercially available enzymes could be identified at Fraunhofer IGB which catalyse peracid formation and thus in a subsequent step an epoxidation of unsaturated fatty acids. The enzymes are currently being characterized and investigated for their technical applications. In addition, appropriate immobilization and, where appropriate, enzyme modifications at the protein level could contribute to increased biocatalyst activity and stability.

Process development

For the chemo-enzymatic epoxidation of vegetable oils and fatty acids, we at Fraunhofer IGB mainly use vegetable oils that are not used as foodstuffs. We were able to optimize the process for the conversion of different substrates with an immobilized lipase from Candida antarctica (Novozym® 435) with regard to substrate concentration, hydrogen peroxide addition, amount of enzymes used and temperature in such a way that various unsaturated fatty acids and oils are almost completely converted to the corresponding epoxides. Following process development on a laboratory scale, the Fraunhofer CBP is to increase the scale and create process diagrams for a production plant on a technical scale and evaluate its economic efficiency.

• Screening for suitable enzymes for epoxidation
• Provision of biotechnologically produced sample quantities of epoxides based on various vegetable oils, free fatty acids and fatty acid esters
• Detailed characterization of vegetable oil oxides (thin layer chromatography, iodine number, epoxy oxygen content, FT-IR, rheology, dynamic differential calorimetry, GC)
• Optimization of relevant process parameters by means of statistical design of experiments
• Scaling up to 100 L scale.

Haitz F, Radloff S, Rupp S, Fröhling M, Hirth T, Zibek S (2018) Chemo-Enzymatic Epoxidation of Lallemantia IbericaSeed Oil: Process Development and Economic-Ecological Evaluation. Applied biochemistry and biotechnology, vol 185. doi: https://doi.org/10.1007/s12010-017-2630-1