Response surface methodology for optimization of enzymatic acylation of (R)‐(‒)‐linalool application to essential oils

Abstract

Linalool (3, 7-dimethylocta−1,6-dien-3-ol) is an acyclic tertiary monoterpene alcohol that is present naturally in almost all essential oils in varying concentration degrees. 1,2 It is utilized generally in perfumery and many flowery fragrance compositions for fruityfresh odours such as neroli, lavender, and lily of the valley. 3 Linalool was included in the list of class "A" substances due to its usefulness as primal matter for the synthesis of high-value added compounds, such as their ester derivatives, 4,5 especially the acetate form. 6,7 Unlike linalool, linalyl acetate is also used as safe flavour adjuvants in food industries due to their high stability and low toxicity and in addition to their pharmacological properties such as antioxidant, antibacterial, or anti-inflammatory activities. [8][9][10] Linalool exists naturally as two isomeric forms, the 3R-(−)-linalool called licareol (odour threshold 0.8 ppb) that has a lavender or lily-of-the-valley odour and the dextrorotatory isomer is 3 S-(+)-linalool called coriandrol (odour threshold 7.4 ppb) that has a herbaceous and musty green smell 11 Licareol is the most common isomeric form; both enantiomers are available in nature, and the stereoisomeric composition of this alcohol influences the olfactory properties of the essential oils containing it. 4,5 For example, the enantiomeric distribution of (R)-(−) and (S)-(+) forms of linalool and linalyl acetate are important indicators of lavender oil purity. 12 Traditionally, monoterpene esters are obtained by conventional chemical synthesis or by extraction from plants. 13,14 However, the extraction and purification way remains less viable due to the large amount of raw material needed, high costs, and the smaller essential oil yield to meet the high industrial demand, 15 while the chemical ways use harmful reagents and causing environment pollution. 16,17 To circumvent those disadvantages and according to the increase demand for greener, environment-friendly processes, biocatalysis seems the ideal