Abstract
Candida stellata is an imperfect yeast of the genus Candida that belongs to the order Saccharomycetales, while phylum Ascomycota. C. stellata was isolated originally from a must overripe in Germany but is widespread in natural and artificial habitats. C. stellata is a yeast with a taxonomic history characterized by numerous changes; it is either a heterogeneous species or easily confused with other yeast species that colonize the same substrates. The strain DBVPG 3827, frequently used to investigate the oenological properties of C. stellata, was recently renamed as Starmerella bombicola, which can be easily confused with C. zemplinina or related species like C. lactis-condensi. Strains of C. stellata have been used in the processing of foods and feeds for thousands of years. This species, which is commonly isolated from grape must, has been found to be competitive and persistent in fermentation in both white and red wine in various wine regions of the world and tolerates a concentration of at least 9% (v/v) ethanol. Although these yeasts can produce spoilage, several studies have been conducted to characterize C. stellata for their ability to produce desirable metabolites for wine flavor, such as acetate esters, or for the presence of enzymatic activities that enhance wine aroma, such as β-glucosidase. This microorganism could also possess many interesting technological properties that could be applied in food processing. Exo and endoglucosidases and polygalactosidase of C. stellata are important in the degradation of β-glucans produced by Botrytis cinerea. In traditional balsamic vinegar production, C. stellata shapes the aromatic profile of traditional vinegar, producing ethanol from fructose and high concentrations of glycerol, succinic acid, ethyl acetate, and acetoin. Chemical characterization of exocellular polysaccharides produced by non-Saccharomyces yeasts revealed them to essentially be mannoproteins with high mannose contents, ranging from 73–74% for Starmerella bombicola. Numerous studies have clearly proven that these macromolecules make multiple positive contributions to wine quality. Recent studies on C. stellata strains in wines made by co-fermentation with Saccharomyces cerevisiae have found that the aroma attributes of the individual strains were apparent when the inoculation protocol permitted the growth and activity of both yeasts. The exploitation of the diversity of biochemical and sensory properties of non-Saccharomyces yeast could be of interest for obtaining new products.
Highlights
The results showed that D1/D2 domain sequences of the C. stellata strains isolated from French cider by Coton et al [50] and from Spanish wine by Hierro et al [38] and the corresponding sequence of Candida sp. isolated from Californian sweet botrytized wine by Mills et al [7] are coincident with those of the type strain of C. zemplinina
In regard to glycerol formation, this behavior of C. stellata is probably owing to low alcohol dehydrogenase activity (4-fold lesser than S. cerevisiae) and high glycerol-3-phosphate dehydrogenase activity (40-fold higher than S. cerevisiae); this higher Gpd activity causes a strong deviation towards glycerol production [67] (Figure 2, in red)
Numerous works have been based on glycosidase activities in yeasts of an oenological origin; in particular, some of them have observed β-glucosidase activity in C. stellata strains possibly related to the fruity and floral aroma found in the wines elaborated with these strains [4,87,103,113,114]
Summary
The genus Candida belongs to the order Saccharomycetales of the phylum Ascomycota and is defined as incerta sedis (of uncertain placement). Some species have been implicated in the conversion of foods and feeds for thousands of years. Their high biochemical potency makes Candida useful for commercial and biotechnological processes. The diversity of the genus is reflected by an amplitude of unique species with respect to colony texture, microscopic morphology, and fermentation and assimilation profiles. The members of this genus may ferment a lot of sugars, assimilate the nitrate, and form pellicles and films on the surface of liquid media. Some species assimilate the inositol and normally the urease is not produced, and gelatin may be liquefied. The inositol assimilation might be positive or negative; in the case of the inositol-positive response, most strains develop pseudomycelia [2]
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