Abstract
2-Phenylethanol (2-PE) is an important flavouring ingredient with a persistent rose-like odour, and it has been widely utilized in food, perfume, beverages, and medicine. Due to the potential existence of toxic byproducts in 2-PE resulting from chemical synthesis, the demand for “natural” 2-PE through biotransformation is increasing. L-Phenylalanine (L-Phe) is used as the precursor for the biosynthesis of 2-PE through the Ehrlich pathway by Saccharomyces cerevisiae. The regulation of L-Phe metabolism in S. cerevisiae is complicated and elaborate. We reviewed current progress on the signal transduction pathways of L-Phe sensing, uptake of extracellular L-Phe and 2-PE synthesis from L-Phe through the Ehrlich pathway. Moreover, the anticipated bottlenecks and future research directions for S. cerevisiae biosynthesis of 2-PE are discussed.
Highlights
Saccharomyces cerevisiae is generally recognized as safe (GRAS) and is typically used in food and industrial production
Saccharomyces cerevisiae recognizes extracellular L-Phe through the SPS-sensing pathway, regulates the expression of genes that are critical for the transport of L-Phe, and recognizes intracellular L-Phe through the target of rapamycin (TOR)-sensing pathway
The currently known transporters involved in the transport of L-Phe are Agp1p, Bap2p, Bap3p, and Gap1p
Summary
2-Phenylethanol (2-PE) is a higher alcohol with a rose-like odour. 2-PE contributes significantly to the flavour and aroma of beer, bread, cocoa, cheese, soy sauce, and other fermented foods and has been widely used in the perfume, cosmetics, and food industries (Chung et al, 2000; Stark et al, 2002). 2-PE is the precursor for the production of 2-phenylethyl acetate (2-PEA), which is an important flavouring agent with floral and rose-like odours (Carlquist et al, 2015). 2-Phenylethanol (2-PE) is a higher alcohol with a rose-like odour. 2-PE is the precursor for the production of 2-phenylethyl acetate (2-PEA), which is an important flavouring agent with floral and rose-like odours (Carlquist et al, 2015). 2-PE is utilized in sanitation and hygiene products, which mainly rely on its antifungal and antibacterial characteristics (Etschmann et al, 2002). The Flavour and Extract Manufacturers Association (FEMA), the Food and Drug Administration (FDA), the Joint Expert Committee on Food Additives (JECFA), the Council of Europe (COE), and other international organizations have approved the use of 2-PE as a flavouring agent in food (Scognamiglio et al, 2012). Most 2-PE is synthesized by chemical methods, including the Friedel-Craft reaction of ethylene oxide with benzene, catalytic reduction of styrene oxide, and oxidation of propylene with
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