Factors Affecting the Yield in Formation of Fat-Derived Fragance Compounds by _Yarrowia lipolytica_ Yeast  
[PERSON] 12 and [PERSON]  
Department of Chemistry, Institute of Food Sciences, Warsaw University of Life Sciences, 02-776 Warsaw, Poland; [EMAIL_ADDRESS] 1  
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additives market. It is estimated that the aroma compounds market will rise from 13.31 to 19.72 bn USD between 2018 and 2026, which puts the compound annual growth rate CAGR at 5% [7]. Factors like emerging health consciousness and personal well-being trends are expected to further drive the demand for natural fragrance ingredients and increase the natural aroma chemicals market. The natural fragrance segment accounts for 40% of the global natural and synthetic fragrance market, since natural aromas appear safer, healthier, and more sustainable [8; 9]. A route for natural fragrance synthesis that offers an alternative to extraction from plants is microbial biosynthesis or bioconversion [10; 11; 12; 13]. Microorganisms can synthesize fragrances as secondary metabolites during fermentation. Fragrances can be generated in situ as integral parts of food and beverages (e.g., cheese, yogurt, and wine) that determine the organoleptic properties of the final product, or obtained in designed reactions catalyzed by microorganisms. A number of enzymes (e.g., glucosidases, lipases, proteases, oxidoreductase) catalyze the production of flavor and fragrance compounds from precursor molecules, including lipids. The biosynthesis of fat-derived fragrance compounds is a multipath, complex process. It often begins with the biosynthesis of fatty acids, specifically with the biosynthesis of unsaturated fatty acids, where the activity of enzymes from the host's desaturase system is required [14]. The compounds synthesized from fatty acids and mediated by microorganisms include, among others, gamma-decalactone (GDL) and compounds from the so-called green fragrance notes. Gamma-decalactone (C\({}_{10}\)H\({}_{18}\)O\({}_{2}\)) is a cyclic 4-hydroxdecanoic acid ester. Its pure form is an oily colorless or slightly yellow liquid, characterized by an intense peach-creamy aroma and perceptible at very low concentrations of 0.088 ppm in aqueous solutions [15]. The \(R\)-enantiomer of GDL naturally occurs in many fruits, especially in peaches, strawberries, and apricots. It has also been detected in butter, milk, cheese, beer, rum, and white and red wine [16]. GDL has GRAS (Generally Recognized As Safe) status and is considered a safe food additive approved by the FDA (Food and Drug Administration). It is widely used in the production of bakery products, confectionery, desserts, and beverages [17]. The biotechnological synthesis of GDL is based on the biotransformation of ribonucleic acid (\(R\)-12-hydroxy-9-_cis_-octadecenoic acid) or its derivatives (mainly methyl ester) in the presence of microorganisms. For economic purposes, castor oil is commonly used, in which ribonucleic acid constitutes nearly 90% of triglycerides. The pathway of degradation of lipids begins with extracellular lipases that hydrolyze triacylglycerlecrols to free fatty acids (Scheme 1). In turn, ribonucleic acid participates in the \(\beta\)-oxidation pathway in which the chain shortens. As a result of four cycles of \(\beta\)-oxidation, 4-hydroxydecanoic acid is obtained, which, under appropriate conditions (after acidification to pH 2.0 and/or heating), undergoes intramolecular esterification--lactonization [18; 19]. In the biotechnological production of GDL, both yeast and fungi [20] have been applied, including _Yarrowia lipolytica_[21], _Candida sorbophila_[22], _Sporobolomyces odorus_[23], _Sporoidiobolus salmonicolor_ and _Sporidiobolus ruineni_[18; 24], and _Rlodotuta aurantiuca_[25].