Les levures du vin

Les levures du vin
Vendredi 18 Novembre 2011,
14h à 17h, Amphi ISVV
Amparo Quérol,
Instituto de Agroquímica y Tecnología de los Alimentos, CSIC.
Apartado de Correos 73, E46100 Burjassot, Valencia, Spain.
[email protected]
Study of the role of Saccharomyces hybrid
strains during fermentation processes
Philippe Marullo,
Institut des Sciences de la Vigne et du Vin
Unité de Recherche Oenologie.
[email protected]
Etude de la variabilité technologique
des souches de Saccharomyces cerevisiae,
approches génétiques et applications
Les levures du vin
Vendredi 18 Novembre 2011,
14h à 17h, Amphi ISVV
Philippe Marullo,
Institut des Sciences de la Vigne et du Vin
Unité de Recherche Oenologie.
[email protected]
Etude de la variabilité technologique des souches de Saccharomyces
cerevisiae, approches génétiques et applications
La variabilité technologique des souches de levure de l’espèce S. cerevisiae est exploitée depuis des
décennies dans l’industrie agroalimentaire. Les levures oenologiques n’échappent pas à cette règle et
sont issues de programmes de sélection génétique. Les principales méthodes reposent sur la sélection
clonale et le croisement d’individus par des approches de breeding. Depuis une dizaine d’années de
nombreux efforts ont été accomplis dans l’identification de variants génétiques responsables de la
différence technologique observée entre les souches. La découverte de ces gènes peut être réalisée par
des approches comparatives telles que la cartographie de QTL. Une fois identifiés, ces variants
génétiques sont utilisés dans des programmes de sélection de souches. Cet exposé tentera de présenter
les avancées réalisées dans ce domaine au sein de l’ISVV.
Les levures du vin
Vendredi 18 Novembre 2011,
14h à 17h, Amphi ISVV
Amparo Quérol,
[email protected]
Instituto de Agroquímica y Tecnología de los Alimentos, CSIC.
Apartado de Correos 73, E46100 Burjassot, Valencia, Spain.
Study of the role of Saccharomyces hybrid strains during fermentation processes
Wine fermentation is a complex ecological and biochemical process involving the sequential development of different yeasts, fungi and
bacteria. Although different yeast species and genera are present in musts, only the species of the Saccharomyces genus are responsible
of the alcoholic fermentation (Pretorius, 2000). The physiological characterization of industrial Saccharomyces strains showed that, in
addition to their high fermentative capabilities, these yeasts produce secondary metabolites, which have an essential influence on the
quality of wines. Some of them are, for example, glycerol, of great interest in winemaking, or higher alcohols andesters, main components
of the secondary aromas (Fleet & Heard, 1993; Lambrechts & Pretorius, 2000).
Although S. cerevisiae is the predominant species responsible of the alcohol fermentation, other closely related species, belonging to the
so-called Saccharomyces sensu stricto complex (new Saccharomyces genus according to Kurtzman, 2003), may have an important role
during fermentation processes. For instance, S. kudriavzevii specieswas isolated from decayed leaves in Japan (Naumov et al., 2000)
and recently from oak barks in Portugal (Sampaio & Gonçalves, 2008) and Spain (Lopes et al.,2010). In spite of not being involved in
winemaking, S. kudriavzevii participate in hybridization processes with other Saccharomyces species like S. cerevisiae or Saccharomyces
bayanus var. uvarum (Saccharomyces uvarum) (Belloch et al., 2009; Gónzalez et al., 2006; Sipiczki, 2008). Besides, this species produce
higher glyceroland lower ethanol amounts than S. cerevisiae (Arroyo-López et al., 2010; Gangl et al., 2009; Gónzalez et al., 2007) and is
able to grow at low temperatures (10ºC) andat higher ones (up to 30ºC), however they are not able to tolerate more than 5% of ethanol
(Belloch et al., 2008). Contrarily, S. cerevisiae is the most important species involved in winemaking and the closely related species
Saccharomyces uvarum can also participate (for a review see Sipiczki, 2002, 2008). From the oenological point ofview, these
Saccharomyces species differ in several properties. Comparison between S. uvarum and S. cerevisiae reveals that the former is more
cryotolerant, produces smaller acetic acid quantities. Wines produced by S. uvarum strains have a higher aromatic intensity than those
produced by S. cerevisiae (Coloretti et al., 2006; Henschke et al., 2000).
Our group has described for the first time the presence of S. cerevisiae x S. kudriavzevii hybrids among wine strains, including a triple
hybrid S. cerevisiae x S. kudriavzeviix S. bayanus (Gonzalez et al., 2006 and 2008). As we comment before, S. kudriavzevii is a species
from natural habitats, never found until now in fermentative processes However, its hybrids are predominant in low temperature
fermentations from Central Europe. The enological characterization of several wine hybrids showed that these strains maintained the
etanol tolerance and the ability to grow in media containing high levels of sugar from the S. cerevisiae parent and improved growth at
lower temperatures from the S. kudriavzevii parent, an interesting property according to the new trends in winemaking. Other interesting
winemaking properties of these hybrids are their higher glycerol synthesis, the lower acetic acid production, and the higher release and
production of flavors and aromas (CITAS).
The DNA chip analyses of yeast gene expression during microvinification (CITAS Mariana y Gamero), indicate that hybrids exhibit a
significant higher expression of thegenes involved in the glycerol synthesis (GPP1 y 2); in the adaptation (stress response) to low
temperatures due to an over-expression of the genes related with thesynthesis of ergosterol (ERG1 and ERG3, ERG11, ERG26) and of
cold-shock genes (TIR1, TIR2, PAU3, PDR5, YHB1and TIP1). In addition, we also detected an overexpressionof some genes encoding
amino acid transporters (AGP1, FUR4, RHB1, BAP3).
Hybrids contain a complex and redundant genome coming from different parent species. To decipher the genome composition of the
hybrids, we performed comparativegenome hybridization with DNA chips. This way, we could observe in the hybrids a series of
recombination events between “homeologous” chromososmes (i.e. homologouschromosomes coming from different parent species).
These recombination events were confirmed by the analysis of presence/absence of 37 gene regions located at thechromosomal ends of
Saccharomyces (CITAS Belloch y Peris).
The study of natural hybrids present in fermentation processes opens a new strategy for the
development of novel industrial yeasts: the generation of artificial hybrids.Producing hybrids between
S. cerevisiae wine strains and other species could be a useful strategy for acquiring yeasts with novel
enological characteristics from speciesthat are less suited for grape juice fermentation. For example,
crosses between S. cerevisiae strains of high fermentation capabilities and excellent enological
propertiesand strains from other Saccharomyces species may generate new strains possessing the
enological properties of the S. cerevisiae parent but acquiring, as occurs in naturalhybrids, interesting
winemaking characteristics from the other parent (CITA LAURA). The species S. kudriavzevii seems to
be very interesting for this purpose because it isadapted to survive in natural habitats (soils and
decayed leaves) under conditions not or less suitable for other species of the genus Saccharomyces,
which conferredunique physiological properties to this species. Moreover, the main advantage of this
method is that it is considered safe and not classified as genetic modification.