Abstract
The pivotal role of non-conventional yeast (NCY) species in formation of valuable aroma compounds in various food commodities is widely acknowledged. This fact inspires endeavors aiming at exploitation of food-derived NCYs as biocatalysts in natural aromas production. In this study, we isolated, characterized and evaluated aroma-producing capacity of two NCY representatives—Pichia cactophila 7.20 and Klyuveromyces lactis 6.10 strains. The strains were isolated from food-related habitats—goat-milk regional cheese and Swiss-type ripening cheese, respectively. Aroma profiles generated by the two strains cultured in a general rich medium were analyzed through solvent extraction and GC-MS analysis of the compounds retained in the culture media. Finally, the strains were tested in bioconversion cultures with branched chain- or aromatic amino acids as the sole nitrogen source, to assess capability of the strains towards formation of amino acid-derived aromas. The results showed extraordinary capacity of both strains for production of 2-phenylethanol (at more than 3 g/L) and isoamyl alcohol (approx. 1.5 g/L). A distinctive trait of 2-phenylethyl acetate synthesis at high concentrations (0.64 g/L) was revealed for P. cactophila 7.20 strain. Highly valued disulfide dimethyl as well as methionol acetate were identified amongst the aroma compounds synthesized by the strains.
Highlights
Top five worldwide leading producers of flavors and fragrances, like International Flavours and Fragrances, Givaudan, Symrise, or Firmenich jointly indicate the urgent need for innovative solutions allowing for production of natural aroma compounds
Yeast strains belonging to K. lactis, K. marxianus, and D. hansenii species are contained in the starter cultures used in industrial production of cheeses [18]
According to the literature data, amongst the non-conventional yeast (NCY) species most frequently isolated from various cheeses one can identify primarily different Candida species, followed by K. marxianus and K. lactis, Pichia spp
Summary
Top five worldwide leading producers of flavors and fragrances, like International Flavours and Fragrances (www.iff.com), Givaudan (www.givaudan.com), Symrise (www.symrise.com), or Firmenich (www.firmenich.com) jointly indicate the urgent need for innovative solutions allowing for production of natural aroma compounds. Synthesis of the aroma compounds in a course of biocatalytic conversion of a structurally-related precursor into the targeted chemical molecule frequently appears to be a superior strategy, which allows for accumulation of a desired flavor compound in significantly higher amounts [2]. Examples of such bioconversions have been extensively described in the literature, for instance, synthesis of vanillin from ferulic acid or eugenol, γ-decalactone—from ricinoleic acid, isoamyl alcohol—from L-Leu, and 2-phenylethanol—from L-Phe [14,15]. Assessment of the NCY strains potential in bioconversion of amino-acid precursors into valuable aroma compounds was conducted
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