Use of Yeast Mannoproteins by Oenococcus oeni during Malolactic Fermentation under Different Oenological Conditions

Abstract

Oenococcus oeni is the main agent of malolactic fermentation in wine. This fermentation takes place after alcoholic fermentation, in a low nutrient medium where ethanol and other inhibitor compounds are present. In addition, some yeast-derived compounds such as mannoproteins can be stimulatory for O. oeni. The mannoprotein concentration in wine depends on the fermenting yeasts, and non-Saccharomyces in particular can increase it. As a result of the hydrolytic activity of O. oeni, these macromolecules can be degraded, and the released mannose can be taken up and used as an energy source by the bacterium. Here we look at mannoprotein consumption and the expression of four O. oeni genes related to mannose uptake (manA, manB, ptsI, and ptsH) in a wine-like medium supplemented with mannoproteins and in natural wines fermented with different yeasts. We observe a general gene upregulation in response to wine-like conditions and different consumption patterns in the studied media. O. oeni was able to consume mannoproteins in all the wines. This consumption was notably higher in natural wines, especially in T. delbrueckii and S. cerevisiae 3D wines, which presented the highest mannoprotein levels. Regardless of the general upregulation, it seems that mannoprotein degradation is more closely related to the fermenting medium.

Discovering the Influence of Microorganisms on Wine Color

“…A recent study revealed that the use of M. pulcherrima , Z. bailii , Candida zeylanoides , and T. delbrueckii increased the content of monomeric anthocyanin in Tempranillo wines improving their color and health properties ( Escribano-Viana et al, 2019 ). Similar results concerning T. delbrueckii were obtained by Balmaseda et al (2021) . These authors revealed that the use of T. delbrueckii improved the volatile complexity and polyphenolic composition of wines and enabled spontaneous MLF.…”

“…Several studies recognized a key role of MPs in the determination of wine color. MPs are polysaccharides released by yeast cells during wine fermentation and during aging of wine on lees by endo-glucanases, exo-D-mannose, and α-D-mannosidase ( Arévalo Villena et al, 2005 ; Belda et al, 2016 ; Balmaseda et al, 2021 ). These proteins are mainly composed of mannose and glucose with a protein content ranging between 1 and 10% with a molecular weight ranging from 50 to 500 kDa ( Yue et al, 2021 ).…”

“…The MPs’ influence on wine color is also dependent upon the strain of yeast used ( Escot et al, 2001 ). Even if S. cerevisiae cell wall is considered the main source of MPs, also some NS yeasts such as Schizosaccharomyces pombe, Pichia fermentans, M. pulcherrima, Saccharomycodes ludwigii, T. delbrueckii, Lachancea thermotolerans , and Wickerhamomyces anomalus , demonstrated the ability to produce and release MPs into the wine during aging on lees ( Morata et al, 2006 , 2019 ; Belda et al, 2016 ; Ferrando et al, 2020 ; Balmaseda et al, 2021 ). MPs are released continuously during the growth of several NS yeasts, reflecting a high production of these polysaccharides during the first phase of fermentation ( Domizio et al, 2014 ).…”

Sequential inoculation of flocculent Torulaspora delbrueckii with Saccharomyces cerevisiae increases color density of Pinot Noir wines

“…Polymeric material (PM), such as mannoproteins, which are typically produced in high concentrations during early fermentation and throughout the growth of some strains of T. delbrueckii, have the potential to adsorb monomeric anthocyanins and improve color density and stability of red wines (Balmaseda et al, 2021). T.…”

“…delbrueckii strains also release mannoproteins during lees aging (Balmaseda et al, 2021). These PMs, which also include polysaccharides, could harbor a pool of scavenged pigments to be released later on in the fermentation.…”