Characterizing the Potential of the Non-Conventional Yeast Saccharomycodes ludwigii UTAD17 in Winemaking

Abstract

Non-Saccharomyces yeasts have received increased attention by researchers and winemakers, due to their particular contributions to the characteristics of wine. In this group, Saccharomycodes ludwigii is one of the less studied species. In the present study, a native S. ludwigii strain, UTAD17 isolated from the Douro wine region was characterized for relevant oenological traits. The genome of UTAD17 was recently sequenced. Its potential use in winemaking was further evaluated by conducting grape-juice fermentations, either in single or in mixed-cultures, with Saccharomyces cerevisiae, following two inoculation strategies (simultaneous and sequential). In a pure culture, S. ludwigii UTAD17 was able to ferment all sugars in a reasonable time without impairing the wine quality, producing low levels of acetic acid and ethyl acetate. The overall effects of S. ludwigii UTAD17 in a mixed-culture fermentation were highly dependent on the inoculation strategy which dictated the dominance of each yeast strain. Wines whose fermentation was governed by S. ludwigii UTAD17 presented low levels of secondary aroma compounds and were chemically distinct from those fermented by S. cerevisiae. Based on these results, a future use of this non-Saccharomyces yeast either in monoculture fermentations or as a co-starter culture with S. cerevisiae for the production of wines with greater expression of the grape varietal character and with flavor diversity could be foreseen.

Genome sequencing, annotation and exploration of the SO2-tolerant non-conventional yeast Saccharomycodes ludwigii

“…No genes encoding enzymes for the synthesis of spermidine, spermine or putrescine, or for biosynthesis of methionine through the salvaging pathway (the main source of percursors for the biosynthesis of polyamines) were found in the genome of UTAD17, similar to what was observed for Hanseniaspora species [ 33 , 45 ]. Although this observation is intriguing, considering that polyamines, and specially spermidine, plays a detrimental role in mediating growth in S. cerevisiae [ 47 ], it is in line with previous reports of the inability of the UTAD17 strain, and of S. ludwigii species in general, to produce biogenic amines (which are produced from polyamines) [ 48 , 49 ]. Another noticeable difference between S. ludwigii UTAD17 and its sister species Hanseniaspora species was the observation that S. ludwigii is equipped with specific permeases for methionine, GABA, histidine, proline, glutamine, lysine, arginine, choline, isoleucine/valine/isoleucine, besides encoding five putative general amino acid permeases while Hanseniaspora encodes only two specific amino acid permeases but thirteen general amino acid permeases (Fig.…”

“…One of the aspects for which S. ludwigii is considered to have strong biotechnological potential is its use in tailored flavour-fermented beverages [ 5 , 26 , 29 , 48 – 50 ]. In this context, we searched the UTAD17 ORFeome for genes predicted to be involved in formation of volatile aroma compounds, with the more relevant aspects of this analysis being summarized in the metabolic map shown in Fig.…”

“…[ 4 ]), was hypothesized to result from the activity of a specific set of putative set alcohol acetyl transferases only found in the genomes of these species [ 33 ] and whose functional characterization is being pursued in our laboratory. Strikingly, although the UTAD17 strain is equipped with enzymes leading to synthesis of ethyl esters and S. ludwigii is known for high capability to produce ethyl esters [ 5 , 28 , 29 , 52 ], during fermentation of natural grape juice the production of these volatiles by UTAD17 cells was almost negligible, even below the one exhibited by S. cerevisiae [ 48 ]. Further investigations will have to be performed to better understand this observation specially focusing whether this trait is specific of the UTAD17 strain (which by some reason could have the activity of alcohol acetyl-transferase enzymes impaired) or whether this resulted from the composition of the grape juice used in the fermentations that could be less favourable for production of ethyl esters by S. ludwigii cells.…”

The Genus Metschnikowia in Enology

“…During the last decade, specific strains of non- Saccharomyces species have been reported as being able to improve different technological and sensory parameters of wine (e.g., aroma complexity, color stability, acidity, polysaccharide production, and clarification) [ 2 , 3 ]. Their use seems to be focused on reducing the ethanol content of wines and increasing the release of mannoproteins together with the impact of hydrolytic enzymes in extracting color and aroma precursors from grapes [ 4 , 5 ]. On the contrary, some of the challenges linked with the use of non- Saccharomyces species in modern winemaking are related to their low fermentation power and low tolerance to SO 2 , along with difficulties in upscaling production for ADYs.…”

Recent Advances in Applied Microbiology: Editorial

“…Regarding the production of alcoholic beverages, Pereira et al [ 13 ] studied the volatile composition and sensory properties of mead produced using free and immobilized yeasts. Another Portuguese study by Esteves et al [ 14 ] provided evidence that non-conventional yeast Saccharomycodes ludwigii has potential for wine production, either in monoculture fermentation or as a co-starter culture with Saccharomyces cerevisiae.…”