2. Alcoholic Beverages Consumption and Health-Promoting Compounds
PThe preventi
ngon of diseases by altering lifestyle and dietary conduct
s may present more benefits than medical care. Up till now, adjusting individual
nutritionaldietary habits
has been is a challenge.
CMost often, consumers must
often choose between nutrition, taste, price, convenience, and cost
[7]. Nowadays, the nutritional value appears to be the health benefit that
has the most impact
s on a consumer’s purchase
[8].
Oxidative stress and antioxidant deficiency have been implicated in the pathogenesis of many diseases and conditions, including atherosclerosis, cancer, aging, and respiratory disease. Glutathione (L-g-glutamyl-L-cysteinyl-glycine, GSH) (
Figure 1) is a
significma
ntjor antioxidant acting as a free radical scavenger that protects the cell from ROS (reactive oxygen species). In addition, GSH is involved in nutrient metabolism and regulation of cellular metabolic functions ranging from DNA and protein synthesis to signal transduction, cell proliferation, and apoptosis
[9][10][11][12,13,14].
Figure 1.
Chemical Structures of the health-promoting compounds mentioned.
Another
vi
talmportant molecule is trehalose (
Figure 1). This sugar
also possesses inflammatory properties
[12],[15] presenting
, also, the ability to protect cellular membranes and labile proteins against denaturation
due toas a result of desiccation and oxidative stress
[13][16].
Yeast metabolism produces compounds derived from tryptophan
, in which are found in fermented beverages, such as wine and beer. In particular, melatonin and serotonin (
Figure 1). Serotonin is a neurohormone that regulates circadian rhythms
, and also has an alleged protective effect against neurodegenerative and degenerative diseases (Alzheimer’s, Parkinson’s
, and Angiogenesis)
[14][17]. Moreover, serotonin is a neurotransmitter itself
, and a precursor of melatonin synthesis.
In humans, melatonin (N-acetyl-5-methoxytryptamine) is a hormone that modulates several physiological processes. This molecule is an indole
-amine found in many living organisms like plants, microorganisms, and humans. Melatonin modulates many human physiological processes
, including the sleep/wake cycle and the reproductive physiology via a receptor-mediated mechanism
[15][16][18,
19] acting
, a
s also, as an antioxidant via nonreceptor
methodprocesses
[17][20]. It is well known that the intake of foods containing melatonin increases its level in plasma and the number of melatonin-derived metabolites
[18][21]. Studies have
been carri
dentifieded out to identify melatonin in grapes
[19][22] and beverages such as beer and wine
[20][21][23,24]. Interesting is the reported concentrations of melatonin in grapes (
Vitis vinifera L.) and wines: 150 µg/g in Merlot grapes
[22][25];
and 130 ng/mL in Tempranillo wine
[23][26].
Tyrosol and tryptophol (
Figure 1) are produced by yeasts during alcoholic fermentation from the catabolism of
the amino acids tyrosine and tryptophan, respectively
. In contrast,, whereas hydroxytyrosol is produced by
the hhydroxylation of its precursor
, tyrosol. Tyrosol, hydroxytyrosol,
and tryptophol are reported to possess several health-enhancing activities, deriving from their free radical scavenging, anticarcinogenic, cardioprotective (induces myocardial protection against ischemia-related stress
[24][27])
, and antimicrobial properties
[25][28].
DIt´s due to the presence of tyrosol and caffeic acids (
Figure 1),
that white wine has been reported as having cardioprotective benefits. Tyrosol and caffeic acids
can are able to activate the cell survival signaling pathway and the
FOXO3a longevity-associated gene
[26][27][29,30]. Moreover, tyrosol has been shown to have an
esseimportant
ial role in the taste of some alcoholic beverages, such as sake
[28][31] and wine
[32] [29],by exhibiting a bitter taste above the sensory threshold
, but below the recognition threshold.
Tryptophol is also
used as a precursor in
the synthesi
zins of the drug Indoramin, an α-adrenoreceptor blocking drug used to treat hypertension [
33]
, and
in the treatment of benign prostatic hyperplasia
[30][34].
Phenylethanol (
Figure 1), also produced by
Candida albicans as an auto-antibiotic
[31][35] is an aromatic compound
that is commonly found in plants, such as roses, possessing
a pleasant floral rose-like odor. Due to its preservative properties, phenylethanol is often used in soap-based detergents because of its stability in
primarybasic conditions. Phenylethanol can also
be act as a natural preservative in wine and beer to prevent spoilage
[31][35].
3. Mechanisms of Microbial Resistance to Environment Changes that Produce Health-Promoting Compounds
Conservation and commercialization of yeast cultures in fresh liquid or pressed forms are not economically advantageous. Thus, dehydrated yeasts present numerous advantages, such as lower cost, convenien
cet for transport and storage, and ease of handling
[32][36]. However,
the drying
of the yeasts signifies
susceptiblhighly sensitive transformation processes for microorganism
’s which can lead to cell death or a significant decrease in cell activity potential
[33][37]. The final water volume of the cells, induced by dehydration-rehydration cycles, influence
s the cell
's survival
[34][38], and the modification of plasma membrane fluidity during the dehydration-rehydration cycles affect
s the plasma membrane structure and may induce cell mortality
[35][39].
AIn
increase of contact surface of the cells with air during dehydration also induces accumulation of ROS (reactive oxygen species)—[O
2•− (superoxide anion),
•OH (hydroxyl radical), H
2O
2 (hydrogen peroxide) and ReOOH (hydroperoxides)]—and may contribute to inactivation of several enzymes, leading, also, to cell death
[36][40]. In the
pres
e sence of these stress conditions
, yeasts
canare able to synthesize compounds such as glutathione and trehalose
[37][41].
Glutathione (GSH) is a ubiquitous low molecular weight thiol tripeptide containing glutamate, cysteine, and glycine (Glu-Cys-Gly)
., Iit is present in large amounts in yeasts and it can be found in the reduced or oxidized forms (GSH and GSSG, respectively). Glutathione plays a crucial role in redox equilibrium reactions, protecting the cell from oxidative stress
, by allowing the formation of native disulfide bonds and by scavenging free radicals present in the cytosol; re
sponsesactions mediated via glutathione reductase and glutathione peroxidase
[9][38][12,42].
Hgt1p in yeast
S. cerevisiae was the first identified high-specificity and high-affinity glutathione transporter (Km 54 mM)
[39][43]. Hgt1p belongs to
the oligopeptide transporter family
, which was also found in fungi, plants, and prokaryotes. Genetic and physiological investigations revealed that gene
HGT1 (open reading frame
YJL212c)
as encod
esing a high-affinity glutathione transporter. Yeast strains deleted in
the HGT1 gene
did not show
ed no any detectable plasma membrane glutathione transport. This transporter is required
tofor the uptake
of glutathione from the extracellular medium
[39][43]. Moreover, mitochondria are a primary source of ROS in cells
, and mitochondrial thiols are
, therefore
, primary major ROS targets. Th
e reis phenomenon is exacerbated by the relatively alkaline pH of mitochondri
a exacerbates this phenomenona. Therefore, redox regulation is critical for numerous mitochondrial functions, and yeast strains lacking GSH are unable to grow by respiration due to an accumulation of oxidative damage to mitochondrial DNA. T
he transport of H
2O
2 across yeast cell membranes can be facilitated by transporters such as aquaporins. Hydrogen peroxide causes oxidative stress but also plays
an important role
s as a signaling molecule in
the regulati
ngon of many biological processes
[40][44].
Thiol redox regulation plays a role in the response of cells to oxidative stress conditions. Gostimskaya and Grant
[41][45] emphasize the importance of compartmentalized redox regulation when cells are subjected to oxidative stress conditions. At the same time as cytosolic glutathione represents the first
significma
ntjor pool of thiols, which would be a target of oxidation in response to exposure to an exogenous oxidant,
tit is the mitochondrial glutathione pool
which is crucial for oxidant tolerance.
4. Melatonin and Other Tryptophan Metabolites
In the scientific world, the theme of “wine and health” topics ha
sve been focused mainly on polyphenols
, once these bioactive compounds are present in plants and are released into fermented products. However, yeast also transforms other molecules into biologically active compounds
[16][19]. Since the pioneering work of Sprenger and co-workers
[42],[50] th
eat melatonin molecule
, has been reported as being present in wine, and its presence has been related to the activity of the yeast involved in the fermentation process.
InitiallyOriginally, seen as a unique product of the pineal gland of vertebrates
, called a neurohormone,
it is currentlyat the present, it is considered a ubiquitous molecule
present in most living organisms
[43][51].
Rodriguez-Naranjo and co-workers
[23][26] studied the capacity of different yeasts to produce melatonin during alcoholic fermentation. Different
Saccharomyces yeast strains, used for industrial fermentation of beer or as nutritional complements
, and non-
Saccharomyces yeast strains (
Metschnikowia pulcherrima and
Starmerella bacillaris) were tested by the referred authors to analyze intracellular and extracellular melatonin production in synthetic grape must. Interestingly,
at the beginning of ferme
ntation melatonin was detected
, in the intracellular compartment
at the beginning of fermentation, either in
Saccharomyces or in non-
Saccharomyces strains. Production levels differed among strains
;, being Starmerella bacillaris the non-
Saccharomyces yeast
, that presented the highest concentration. Nevertheless,
depending on the yeast strain, eextracellular melatonin was detected at different time
-points over the fermentation process
, depending on the yeast strain. However, the same authors
[23][26] also reported that t
he pr
esence of tryptophan is essential for melatonin production since it is its principal precursor
;, it increases final melatonin content and
it accelerates its formation. Moreover, the synthesis of melatonin largely depends on the growth phase of the yeast and the concentration of the reducing sugars.
The metabolic pathway for melatonin production in yeast is not
comple
ntirtely clarified
;, nevertheless, the formation of serotonin might be an intermediate metabolite in the pathway
[16][19].
5. Fusel Alcohols Formed Via the Ehrlich Pathway
The synthesis of tryptophol by yeast was first described by Felix Ehrlich in 1912
[44][45][62,63] as the metabolic conversion of amino acids via the successive steps of transamination, decarboxylation, and reduction
[46][64].
Similarly, t
o tryptophol, phenylethanol, and tyrosol
, are phenolic compounds or fusel alcohols formed via the Ehrlich pathway by yeast metabolism. These compounds can yield health benefits a
nds well as contribute to the flavors and aromas of fermented food and beverages
[45][47][63,65].
6. Fermented Beverages Containing Probiotics
It is common knowledge that most
of
e the fermented milk contains probiotic microorganisms (live microorganisms, which
, when administered in adequate amounts, confer a health benefit on the host). Yogurt, the most common product of milk lactose fermentation, has
son its constitution several lactic acid bacteria
in its constitution. So, the domination of milk-based beverages fermented by LAB, mainly
Leuconostoc,
lactobacilli, and
lactococci, is
clea
pparentr. Milk fermentation in colder climates promotes the growth of mesophilic bacteria such as
Lactococcus and
Leuconostoc., In contrast,whereas beverages produced at higher temperatures usually have
more significantgreater counts of thermophilic bacteria such as
Lactobacillus and
Streptococcus [48][49][66,67]. Most
often the probiotic bacteria
often come from
Lactobacillus, or Bifidobacterium, or a cocktail of both
[50][68].
Another class of fermented beverages is those made from cereals (maize, millet, barley, oats, rye, wheat, rice
, and sorghum), w
here the natural microbial component is used to ferment grains. The microbial populations responsible for the fermentation of these beverages are not, yet, well characterized. Of several blends, it has been suggested that fermentation by
S. cerevisiae,
Leuconostoc mesenteroides, and
Lactobacillus confusus produce the most palatable beverages
[48][66].