Biocatalytic production of odour-active fatty aldehydes via inherent rice seedling α-dioxygenase activity

Fatty aldehydes serve as key contributors to the odour profiles of many foods and are essential ingredients in numerous flavourings and fragrances. To meet the growing demand for sustainable and naturally sourced aldehydes, a biocatalytic method employing the inherent α-dioxygenase present in rice seedlings was developed to produce carbon chain-shortened odour-active fatty aldehydes from the corresponding fatty acids. Optimisation of rice cultivation parameters and of reaction conditions strongly increased the product yields. Chemoselectivity studies revealed a clear preference for medium- and long-chain fatty acids i.a. lauric acid, palmitic acid and α-linolenic acid. Surprisingly, rare iso-fatty acids proved to be preferred substrates, enabling the bioconversion into highly valuable methyl-branched aldehydes. Lipid extracts of the fungus Conidiobolus heterosporus, rich in iso-fatty acids, were successfully biotransformed into a complex aldehyde mixture yielding high amounts of i.a. 11-methyldodecanal and 13-methyltetradecanal. This GMO-free biocatalytic approach provides an interesting proof of concept for the synthesis of highly sought-after odour-active fatty aldehydes.