Antimicrobial properties and death-inducing mechanisms of saccharomycin, a biocide secreted by Saccharomyces cerevisiae

Evaluation of Biotechnological Active Peptides Secreted by Saccharomyces cerevisiae with Potential Skin Benefits

Biotechnological active peptides are gaining interest in the cosmetics industry due to their antimicrobial, anti-inflammatory, antioxidant, and anti-collagenase (ACE) effects, as well as wound healing properties, making them suitable for cosmetic formulations. The antimicrobial activity of peptides (2-10 kDa) secreted by Saccharomyces cerevisiae Ethanol-Red was evaluated against dermal pathogens using broth microdilution and challenge tests. ACE was assessed using a collagenase activity colorimetric assay, antioxidant activity via spectrophotometric monitoring of nitrotetrazolium blue chloride (NBT) reduction, and anti-inflammatory effects by quantifying TNF-α mRNA in lipopolysaccharides (LPS)-exposed dermal fibroblasts. Wound healing assays involved human fibroblasts, endothelial cells, and dermal keratinocytes. The peptides (2-10 kDa) exhibited antimicrobial activity against 10 dermal pathogens, with the Minimum Inhibitory Concentrations (MICs) ranging from 125 µg/mL for Staphylococcus aureus to 1000 µg/mL for Candida albicans and Streptococcus pyogenes. In the challenge test, peptides at their MICs reduced microbial counts significantly, fulfilling ISO 11930:2019 standards, except against Aspergillus brasiliensis. The peptides combined with MicrocareⓇ SB showed synergy, particularly against C. albicans and A. brasilensis. In vitro, the peptides inhibited collagenase activity by 41.8% and 94.5% at 250 and 1000 µg/mL, respectively, and demonstrated antioxidant capacity. Pre-incubation with peptides decreased TNF-α expression in fibroblasts, indicating anti-inflammatory effects. The peptides do not show to promote or inhibit the angiogenesis of endothelial cells, but are able to attenuate fibrosis, scar formation, and chronic inflammation during the final phases of the wound healing process. The peptides showed antimicrobial, antioxidant, ACE, and anti-inflammatory properties, highlighting their potential as multifunctional bioactive ingredients in skincare, warranting further optimization and exploration in cosmetic applications.

Insights into Molecular Interactions between a GAPDH-Related Fish Antimicrobial Peptide, Analogs Thereof, and Bacterial Membranes

Interactions between SJGAP (skipjack tuna GAPDH-related antimicrobial peptide) and four analogs thereof with model bacterial membranes were studied using Fourier-transform infrared spectroscopy (FTIR) and molecular dynamics (MD) simulations. MD trajectory analyses showed that the N-terminal segment of the peptide analogs has many contacts with the polar heads of membrane phospholipids, while the central α helix interacts strongly with the hydrophobic core of the membranes. The peptides also had a marked influence on the wave numbers associated with the phase transition of phospholipids organized as liposomes in both the interface and aliphatic chain regions of the infrared spectra, supporting the interactions observed in the MD trajectories. In addition, interesting links were found between peptide interactions with the aliphatic chains of membrane phospholipids, as determined by FTIR and from the MD trajectories, and the membrane permeabilization capacity of these peptide analogs, as previously demonstrated. To summarize, the combined experimental and computational efforts have provided insights into crucial aspects of the interactions between the investigated peptides and bacterial membranes. This work thus makes an original contribution to our understanding of the molecular interactions underlying the antimicrobial activity of these GAPDH-related antimicrobial peptides from Scombridae.

Potential bioactive peptides obtained after in vitro gastrointestinal digestion of wine lees from sequential fermentations

The biotechnological reuse of winery by-products has great potential to increase the value and sustainability of the wine industry. Recent studies revealed that yeast biomass can be an exciting source of bioactive peptides with possible benefits for human health, and its incorporation in plant-based foods is considered innovative and sustainable. In this study, we aimed to identify, through in silico analyses, potential bioactive peptides from yeast extracts after in vitro digestion. Wine lees from a non-Saccharomyces oenological yeast, Starmerella bacillaris FRI751, Saccharomyces cerevisiae EC1118, and sequential fermentation performed with both strains (SEQ) were recovered in a synthetic must. Cellular pellets were enzymatically treated with zymolyase, and the yeast extracts were submitted to in vitro gastrointestinal digestions. LC-MS/MS sequenced the hydrolyzed peptides, and their potential bioactivity was inferred. S. bacillaris FRI751 fermentation showed 132 peptide sequences, S. cerevisiae EC1118 60, SEQ 89. A total of 243 unique peptide sequences were identified across the groups. Furthermore, based on the peptide sequence, the FRI751 extract showed the highest potential antihypertensive with 275 bioactive fragments. Other bioactivities, such as antimicrobial and immunomodulatory, were also identified in all yeast extracts. A potential antiobesity bioactive peptide VVP was identified only in the yeast extract from S. bacillaris single strain. The wine lees from S. bacillaris single strain and SEQ fermentation are a richer source of potential bioactive peptides than those from S. cerevisiae fermentation. This study opens new possibilities in the valorization of winemaking by-products.

Effect of overexpression of partial TDH1 and TDH2/3 gene sequences in a starter strain of industrial bioethanol fermentation on the Brettanomyces bruxellensis contaminant growth

Selected Saccharomyces cerevisiae strains, such as the commercial Ethanol-Red (ER) strain, are used as starters in the bioethanol industry. Yet, bioethanol fermentations are prone to microbial contaminations, mainly by Brettanomyces bruxellensis and lactic acid bacteria. Chemicals, such as sulphuric acid and antibiotics, are commonly used to combat those contaminations, but they have negative environmental impacts. Recently, ER strain was found to secrete antimicrobial peptides (AMPs) active against B. bruxellensis. Therefore, the partial TDH1 and TDH2/3 genes sequences that codify those AMPs were inserted into the pSR41k plasmid and cloned in ER strains. The relative expression levels (plasmidic/genomic) of those sequences in the respective modified ER strains were quantified by real-time quantitative polimerase chain reaction (RT-qPCR), confirming their overexpression. The effect of the modified strains on B. bruxellensis (Bb) growth was then evaluated during synthetic must (SM) and carob syrup (CS) fermentations, co-inoculated with 105 cells ml-1 of ER and Bb in SM and with 106 of ER and 5 × 103 cells ml-1 of Bb in CS. Results showed that modified ER strains exerted a much higher inhibitory effect against B. bruxellensis (72-fold in SM and 10-fold in CS) than the non-modified ER strain. In those fermentations, 90-100 g l-1 of ethanol was produced in 3-6 days.

Exploring the Multifaceted Potential of a Peptide Fraction Derived from Saccharomyces cerevisiae Metabolism: Antimicrobial, Antioxidant, Antidiabetic, and Anti-Inflammatory Properties

The rising demand for minimally processed, natural, and healthier food products has led to the search for alternative and multifunctional bioactive food components. Therefore, the present study focuses on the functional proprieties of a peptide fraction derived from Saccharomyces cerevisiae metabolism. The antimicrobial activity of the peptide fraction is evaluated against various foodborne pathogens, including Candida albicans, Candida krusei, Escherichia coli, Listeria monocytogenes, and Salmonella sp. The peptide fraction antioxidant properties are assessed using FRAP and DPPH scavenging capacity assays. Furthermore, the peptide fraction's cytotoxicity is evaluated in colorectal carcinoma and normal colon epithelial cells while its potential as an antidiabetic agent is investigated through α-amylase and α-glucosidase inhibitory assays. The results demonstrate that the 2-10 kDa peptide fraction exhibits antimicrobial effects against all tested microorganisms, except C. krusei. The minimal inhibitory concentration for E. coli, L. monocytogenes, and Salmonella sp. remains consistently low, at 0.25 mg/mL, while C. albicans requires a higher concentration of 1.0 mg/mL. Furthermore, the peptide fraction displays antioxidant activity, as evidenced by DPPH radical scavenging activity of 81.03%, and FRAP values of 1042.50 ± 32.5 µM TE/mL at 1.0 mg/mL. The peptide fraction exhibits no cytotoxicity in both tumor and non-tumoral human cells at a concentration up to 0.3 mg/mL. Moreover, the peptide fraction presents anti-inflammatory activity, significantly reducing the expression of the TNFα gene by more than 29.7% in non-stimulated colon cells and by 50% in lipopolysaccharide-stimulated colon cells. It also inhibits the activity of the carbohydrate digestive enzymes α-amylase (IC50 of 199.3 ± 0.9 µg/mL) and α-glucosidase (IC20 of 270.6 ± 6.0 µg/mL). Overall, the findings showed that the peptide fraction exhibits antibacterial, antioxidant, anti-inflammatory, and antidiabetic activity. This study represents a step forward in the evaluation of the functional biological properties of S. cerevisiae bioactive peptides.

Molecular de-extinction of ancient antimicrobial peptides enabled by machine learning

Molecular de-extinction could offer avenues for drug discovery by reintroducing bioactive molecules that are no longer encoded by extant organisms. To prospect for antimicrobial peptides encrypted within extinct and extant human proteins, we introduce the panCleave random forest model for proteome-wide cleavage site prediction. Our model outperformed multiple protease-specific cleavage site classifiers for three modern human caspases, despite its pan-protease design. Antimicrobial activity was observed in vitro for modern and archaic protein fragments identified with panCleave. Lead peptides showed resistance to proteolysis and exhibited variable membrane permeabilization. Additionally, representative modern and archaic protein fragments showed anti-infective efficacy against A. baumannii in both a skin abscess infection model and a preclinical murine thigh infection model. These results suggest that machine-learning-based encrypted peptide prospection can identify stable, nontoxic peptide antibiotics. Moreover, we establish molecular de-extinction through paleoproteome mining as a framework for antibacterial drug discovery.

Myxobacterial Outer Membrane β-1,6-Glucanase Induced the Cell Death of Fusarium oxysporum by Destroying the Cell Wall Integrity

The β-1,6-glucan is the key linker between mannoproteins in the outermost part of the cell wall and β-1,3-glucan/chitin polysaccharide to maintain the rigid structure of the cell wall. The β-1,6-glucanase GluM, which was purified from the fermentation supernatant of Corallococcus sp. EGB, was able to inhibit the germination of Fusarium oxysporum f. sp. cucumerinum conidia at a minimum concentration of 2.0 U/mL (0.08 μg/mL). The survival rates of GluM-treated conidia and monohyphae were 10.4% and 30.7%, respectively, which were significantly lower than that of β-1,3-glucanase treatment (Zymolyase, 20.0 U/mL; equate to 1.0 mg/mL) (72.9% and 73.9%). In contrast to β-1,3-glucanase treatment, the high-osmolarity glycerol (HOG) pathway of F. oxysporum f. sp. cucumerinum cells was activated after GluM treatment, and the intracellular glycerol content was increased by 2.6-fold. Moreover, the accumulation of reactive oxygen species (ROS) in F. oxysporum f. sp. cucumerinum cells after GluM treatment induced apoptosis, but it was not associated with the increased intracellular glycerol content. Together, the results indicate that β-1,6-glucan is a promising target for the development of novel broad-spectrum antifungal agents. IMPORTANCE Phytopathogenic fungi are the most devastating plant pathogens in agriculture, causing enormous economic losses to global crop production. Biocontrol agents have been promoted as replacements to synthetic chemical pesticides for sustainable agriculture development. Cell wall-degrading enzymes (CWDEs), including chitinases and β-1,3-glucanases, have been considered as important armaments to damage the cell wall. Here, we found that F. oxysporum f. sp. cucumerinum is more sensitive to β-1,6-glucanase GluM treatment (0.08 μg/mL) than β-1,3-glucanase Zymolyase (1.0 mg/mL). The HOG pathway was activated in F. oxysporum f. sp. cucumerinum cells after GluM treatment, and the intracellular glycerol content was significantly increased. Moreover, the decomposition of F. oxysporum f. sp. cucumerinum cell wall by GluM induced the burst of intracellular ROS and apoptosis, which eventually leads to cell death. Therefore, we suggest that the β-1,6-glucan of the fungal cell wall may be a better antifungal target compared to the β-1,3-glucan.

Combined Effect of Ultrasound Treatment and a Mix of Krebs Cycle Acids on the Metabolic Processes in Saccharomyces cerevisiae

This article describes the effect of organic acids and ultrasound on the physiological and biochemical properties of yeast, which was used to obtain biologically active peptides. The research featured brewer’s yeast S. cerevisiae W-34/70 cultivated in 11% beer wort. A mix of Krebs cycle acids served as an activator. It included succinic, malic, fumaric, citric, and oxaloacetic acids (1:1:1:1:1). The concentration of the Krebs cycle acids was 1 × 10−10 M/L at 1% to the suspension volume. The ultrasound treatment had an intensity of 10 W/m2 and lasted 3–10 min. The combined effect increased the fermentation activity of the yeast by 98%. The activity of individual biocatalysts of constructive and energy metabolism rose by 108–330%, while that of proteolysis enzymes increased by 15% in comparison with the samples exposed to individual factors. The stimulation increased the rate of amine nitrogen consumption by the yeast. The amount of accumulated amino acids was larger by 80% than in the control, and that of protein larger by 7%. The maximal content of the synthesized protein was reached 1–2 h earlier. The combination of chemical and physical factors intensified the biosynthesis of protein and its intermediates during yeast processing, thus facilitating the subsequent extraction of biologically valuable components.

Evaluation of the Biocontrol Potential of a Commercial Yeast Starter against Fuel-Ethanol Fermentation Contaminants

Lactic acid bacteria (LAB) and Brettanomyces bruxellensis are the main contaminants of bioethanol fermentations. Those contaminations affect Saccharomyces cerevisiae performance and reduce ethanol yields and productivity, leading to important economic losses. Currently, chemical treatments such as acid washing and/or antibiotics are used to control those contaminants. However, these control measures carry environmental risks, and more environmentally friendly methods are required. Several S. cerevisiae wine strains were found to secrete antimicrobial peptides (AMPs) during alcoholic fermentation that are active against LAB and B. bruxellensis strains. Thus, in the present study, we investigated if the fuel-ethanol commercial starter S. cerevisiae Ethanol Red (ER) also secretes those AMPs and evaluated its biocontrol potential by performing alcoholic fermentations with mixed-cultures of ER and B. bruxellensis strains and growth assays of LAB in ER pre-fermented supernatants. Results showed that all B. bruxellensis strains were significantly inhibited by the presence of ER, although LAB strains were less sensitive to ER fermentation metabolites. Peptides secreted by ER during alcoholic fermentation were purified by gel-filtration chromatography, and a bioactive fraction was analyzed by ELISA and mass spectrometry. Results confirmed that ER secretes the AMPs previously identified. That bioactive fraction was used to determine minimal inhibitory concentrations (MICs) against several LAB and B. bruxellensis strains. MICs of 1–2 mg/mL were found for B. bruxellensis strains and above 2 mg/mL for LAB. Our study demonstrates that the AMPs secreted by ER can be used as a natural preservative in fuel-ethanol fermentations.

Spent brewer's yeast (Saccharomyces cerevisiae) as a potential source of bioactive peptides: An overview

Bioactive peptides become popular in several economic sectors over the years as they have demonstrated important biological benefits in digestive, immune, cardiovascular, and nervous human systems. Although many commercial peptides are chemically synthesized, they can also be obtained from natural protein sources such as spent brewer's yeast (Saccharomyces cerevisiae). The recovery of this fermentation by-product for production of functional ingredients is an important step in the increasingly demand to implement and promote a circular economy-based industry. Bioactive peptides can be found in protein-rich extracts produced from S. cerevisiae, and several studies have described their positive impact of human body. In this line, the present review highlights and discuss the reported biological properties of S. cerevisiae bioactive peptides in terms of antihypertensive, antioxidant and antimicrobial effects, although other bioactivities are also described. Concerning the growing interest in yeast protein-rich products by agri-food and cosmetic sectors, some of the products currently on the market are also pointed out and their potential source is discussed.

Determination of the Relationships between the Chemical Structure and Antimicrobial Activity of a GAPDH-Related Fish Antimicrobial Peptide and Analogs Thereof

The structure–activity relationships and mode of action of synthesized glyceraldehyde-3-phosphate dehydrogenase (GAPDH)-related antimicrobial peptides were investigated. Including the native skipjack tuna GAPDH-related peptide (SJGAP) of 32 amino acid residues (model for the study), 8 different peptide analogs were designed and synthesized to study the impact of net charge, hydrophobicity, amphipathicity, and secondary structure on both antibacterial and antifungal activities. A net positive charge increase, by the substitution of anionic residues or C-terminal amidation, improved the antimicrobial activity of the SJGAP analogs (minimal inhibitory concentrations of 16–64 μg/mL), whereas the alpha helix content, as determined by circular dichroism, did not have a very definite impact. The hydrophobicity of the peptides was also found to be important, especially for the improvement of antifungal activity. Membrane permeabilization assays showed that the active peptides induced significant cytoplasmic membrane permeabilization in the bacteria and yeast tested, but that this permeabilization did not cause leakage of 260 nm-absorbing intracellular material. This points to a mixed mode of action involving both membrane pore formation and targeting of intracellular components. This study is the first to highlight the links between the physicochemical properties, secondary structure, antimicrobial activity, and mechanism of action of antimicrobial peptides from scombrids or homologous to GAPDH.

A Peptide Derived from GAPDH Enhances Resistance to DNA Damage in Saccharomyces cerevisiae Cells

Social behaviors do not exist only in higher organisms but are also present in microbes that interact for the common good. Here, we report that budding yeast cells interact with their neighboring cells after exposure to DNA damage. Yeast cells irradiated with DNA-damaging UV light secrete signal peptides that can increase the survival of yeast cells exposed to DNA-damaging stress. The secreted peptide is derived from glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and it induced cell death of a fraction of yeast cells in the group. The data suggest that the GAPDH-derived peptide serves in budding yeast's social interaction in response to DNA-damaging stress. IMPORTANCE Many studies have shown that microorganisms, including bacteria and yeast, display increased tolerance to stress after exposure to the same stressor. However, the mechanism remains unknown. In this study, we report a striking finding that Saccharomyces cerevisiae cells respond to DNA damage by secreting a peptide that facilitates resistance to DNA-damaging stress. Although it has been shown that GAPDH possesses many key functions in cells aside from its well-established role in glycolysis, this study demonstrated that GAPDH is also involved in the social behaviors response to DNA-damaging stress. The study opens the gate to an interesting research field about microbial social activity for adaptation to a harsh environment.

Identification of Antibacterial Peptide Candidates Encrypted in Stress-Related and Metabolic Saccharomyces cerevisiae Proteins

The protein-rich nature of Saccharomyces cerevisiae has led this yeast to the spotlight concerning the search for antimicrobial peptides. Herein, a <10 kDa peptide-rich extract displaying antibacterial activity was obtained through the autolysis of yeast biomass under mild thermal treatment with self-proteolysis by endogenous peptidases. Estimated IC₅₀ for the peptide pools obtained by FPLC gel filtration indicated improved antibacterial activities against foodborne bacteria and bacteria of clinical interest. Similarly, the estimated cytotoxicity concentrations against healthy human fibroblasts, alongside selective indices ≥10, indicates the fractions are safe, at least in a mixture format, for human tissues. Nano-LC-MS/MS analysis revealed that the peptides in FPLC fractions could be derived from both induced-proteolysis and proteasome activity in abundant proteins, up-regulated under stress conditions during S. cerevisiae biomass manufacturing, including those coded by TDH1/2/3, HSP12, SSA1/2, ADH1/2, CDC19, PGK1, PPI1, PDC1, and GMP1, as well as by other non-abundant proteins. Fifty-eight AMP candidate sequences were predicted following an in silico analysis using four independent algorithms, indicating their possible contribution to the bacterial inactivation observed in the peptides pool, which deserve special attention for further validation of individual functionality. S. cerevisiae-biomass peptides, an unconventional but abundant source of pharmaceuticals, may be promissory adjuvants to treat infectious diseases that are poorly sensitive to conventional antibiotics.

Bioprotection strategies in winemaking

Worldwide the interest for biological control of food spoilage microorganisms has significantly increased over the last decade. Wine makes no exception to this trend, as consumer demands for wines free of preservatives that are considered negative for human health, increase. Biological control during wine fermentation aims at producing high quality wines, while minimizing, or even eliminating, the use of chemical additives. Its success lies in the inoculation of microorganisms to prevent, inhibit or kill undesired microbes, therefore maintaining wine spoilage at the lowest level. The food industry already makes use of this practice, with dedicated commercial microbes already on the market. In winemaking, there are commercial microbes currently under investigation, particularly with the aim to reduce or replace the use of sulphur dioxide. In this review, the potential of wine yeasts and lactic acid bacteria as bioprotection agents and their mechanisms of action during wine fermentation are presented.

Anti-salmonella properties of kefir yeast isolates: An in vitro screening for potential infection control

The rise of antibiotic resistance has increased the need for alternative ways of preventing and treating enteropathogenic bacterial infection. Various probiotic bacteria have been used in animal and human. However, Saccharomyces boulardii is the only yeast currently used in humans as probiotic. There is scarce research conducted on yeast species commonly found in kefir despite its claimed potential preventative and curative effects. This work focused on adhesion properties, and antibacterial metabolites produced by Kluyveromyces lactis and Saccharomyces unisporus isolated from traditional kefir grains compared to Saccharomyces boulardii strains. Adhesion and sedimentation assay, slide agglutination, microscopy and turbidimetry assay were used to analyze adhesion of Salmonella Arizonae and Salmonella Typhimurium onto yeast cells. Salmonella growth inhibition due to the antimicrobial metabolites produced by yeasts in killer toxin medium was analyzed by slab on the lawn, turbidimetry, tube dilution and solid agar plating assays. Alcohol and antimicrobial proteins production by yeasts in killer toxin medium were analyzed using gas chromatography and shotgun proteomics, respectively. Salmonella adhered onto viable and non-viable yeast isolates cell wall. Adhesion was visualized using scanning electron microscope. Yeasts-fermented killer toxin medium showed Salmonella growth inhibition. The highest alcohol concentration detected was 1.55%, and proteins with known antimicrobial properties including cathelicidin, xanthine dehydrogenase, mucin-1, lactadherin, lactoperoxidase, serum amyloid A protein and lactotransferrin were detected in yeasts fermented killer medium. These proteins are suggested to be responsible for the observed growth inhibition effect of yeasts-fermented killer toxin medium. Kluyveromyces lactis and Saccharomyces unisporus have anti-salmonella effect comparable to Saccharomyces boulardii strains, and therefore have potential to control Salmonella infection.

Wine Spoilage Control: Impact of Saccharomycin on Brettanomyces bruxellensis and Its Conjugated Effect with Sulfur Dioxide

The yeast Brettanomyces bruxellensis is one of the most dangerous wine contaminants due to the production of phenolic off-flavors such as 4-ethylphenol. This microbial hazard is regularly tackled by addition of sulfur dioxide (SO₂). Nevertheless, B. bruxellensis is frequently found at low levels (ca 10³ cells/mL) in finished wines. Besides, consumers health concerns regarding the use of sulfur dioxide encouraged the search for alternative biocontrol measures. Recently, we found that Saccharomyces cerevisiae secretes a natural biocide (saccharomycin) that inhibits the growth of different B. bruxellensis strains during alcoholic fermentation. Here we investigated the ability of S. cerevisiae CCMI 885 to prevent B. bruxellensis ISA 2211 growth and 4-ethylphenol production in synthetic and true grape must fermentations. Results showed that B. bruxellensis growth and 4-ethylphenol production was significantly inhibited in both media, although the effect was more pronounced in synthetic grape must. The natural biocide was added to a simulated wine inoculated with 5 × 10² cells/mL of B. bruxellensis, which led to loss of culturability and viability (100% dead cells at day-12). The conjugated effect of saccharomycin with SO₂ was evaluated in simulated wines at 10, 12, 13 and 14% (v/v) ethanol. Results showed that B. bruxellensis proliferation in wines at 13 and 14% (v/v) ethanol was completely prevented by addition of 1.0 mg/mL of saccharomycin with 25 mg/L of SO₂, thus allowing to significantly reduce the SO₂ levels commonly used in wines (150–200 mg/L).

Yeast interaction on Chardonnay wine composition: Impact of strain and inoculation time

It is of great importance to understand the molecular characteristics and substantial chemical transformations due to yeast-yeast interaction. Non-targeted metabolomics was used to unravel must in fermentation composition, inoculated with non-Saccharomyces (NS) yeasts and Saccharomyces cerevisiae (S) for sequential fermentation. ultrahigh-resolution mass spectrometry was able to distinguish thousands of metabolites and provides deep insights into grape must composition allowing better understanding of the yeast-yeast interactome. The dominance of S, characterized by a metabolic richness not found with NS, is dependent on inoculation time and on the yeast species present. Co-inoculation leads to the formation of new compounds, reflecting a reshuffling of yeast metabolism linked to interaction mechanisms. Among the modifications observed, metabolomic unravels deep changes in nitrogen metabolism due to yeast-yeast interactions and suggests that the redistribution pattern affects two different routes, the pentose phosphate and the amino acid synthesis pathways.

A Systematic Survey of Characteristic Features of Yeast Cell Death Triggered by External Factors

Cell death in response to distinct stimuli can manifest different morphological traits. It also depends on various cell death signaling pathways, extensively characterized in higher eukaryotes but less so in microorganisms. The study of cell death in yeast, and specifically Saccharomyces cerevisiae, can potentially be productive for understanding cell death, since numerous killing stimuli have been characterized for this organism. Here, we systematized the literature on external treatments that kill yeast, and which contains at least minimal data on cell death mechanisms. Data from 707 papers from the 7000 obtained using keyword searches were used to create a reference table for filtering types of cell death according to commonly assayed parameters. This table provides a resource for orientation within the literature; however, it also highlights that the common view of similarity between non-necrotic death in yeast and apoptosis in mammals has not provided sufficient progress to create a clear classification of cell death types. Differences in experimental setups also prevent direct comparison between different stimuli. Thus, side-by-side comparisons of various cell death-inducing stimuli under comparable conditions using existing and novel markers that can differentiate between types of cell death seem like a promising direction for future studies.

Saccharomyces cerevisiae biomass as a source of next-generation food preservatives: Evaluating potential proteins as a source of antimicrobial peptides

Saccharomyces cerevisiae is the main biotechnological tool for the production of Baker's or Brewer's biomasses, largely applied in beverage and fermented-food production. Through its gene expression reprogramming and production of compounds that inactivate the growth of other microorganisms, S. cerevisiae is able to grow in adverse environments and in complex microbial consortia, as in fruit pulps and root flour fermentations. The distinct set of up-regulated genes throughout yeast biomass propagation includes those involved in sugar fermentation, ethanol metabolization, and in protective responses against abiotic stresses. These high abundant proteins are precursors of several peptides with promising health-beneficial activities such as antihypertensive, antioxidant, antimicrobial, immunomodulatory, anti-obesity, antidiabetes, and mitogenic properties. An in silico investigation of these S. cerevisiae derived peptides produced during yeast biomass propagation or induced by physicochemical treatments were performed using four algorithms to predict antimicrobial candidates encrypted in abundantly expressed stress-related proteins encoded by different genes like AHP1, TSA1, HSP26, SOD1, HSP10, and UTR2, or metabolic enzymes involved in carbon source utilization, like ENO1/2, TDH1/2/3, ADH1/2, FBA1, and PDC1. Glyceraldehyde-3-phosphate dehydrogenase and enolase II are noteworthy precursor proteins, since they exhibited the highest scores concerning the release of antimicrobial peptide candidates. Considering the set of genes upregulated during biomass propagation, we conclude that S. cerevisiae biomass, a food-grade product consumed and marketed worldwide, should be considered a safe and nonseasonal source for designing next-generation bioactive agents, especially protein encrypting antimicrobial peptides that display broad spectra activity and could reduce the emergence of microbial resistance while also avoiding cytotoxicity.

Mechanisms Involved in Interspecific Communication between Wine Yeasts

In parallel with the development of non-Saccharomyces starter cultures in oenology, a growing interest has developed around the interactions between the microorganisms involved in the transformation of grape must into wine. Nowadays, it is widely accepted that the outcome of a fermentation process involving two or more inoculated yeast species will be different from the weighted average of the corresponding individual cultures. Interspecific interactions between wine yeasts take place on several levels, including interference competition, exploitation competition, exchange of metabolic intermediates, and others. Some interactions could be a simple consequence of each yeast running its own metabolic programme in a context where metabolic intermediates and end products from other yeasts are present. However, there are clear indications, in some cases, of specific recognition between interacting yeasts. In this article we discuss the mechanisms that may be involved in the communication between wine yeasts during alcoholic fermentation.

Yeast Interactions and Molecular Mechanisms in Wine Fermentation: A Comprehensive Review

Wine can be defined as a complex microbial ecosystem, where different microorganisms interact in the function of different biotic and abiotic factors. During natural fermentation, the effect of unpredictable interactions between microorganisms and environmental factors leads to the establishment of a complex and stable microbiota that will define the kinetics of the process and the final product. Controlled multistarter fermentation represents a microbial approach to achieve the dual purpose of having a less risky process and a distinctive final product. Indeed, the interactions evolved between microbial consortium members strongly modulate the final sensorial properties of the wine. Therefore, in well-managed mixed fermentations, the knowledge of molecular mechanisms on the basis of yeast interactions, in a well-defined ecological niche, becomes fundamental to control the winemaking process, representing a tool to achieve such objectives. In the present work, the recent development on the molecular and metabolic interactions between non-Saccharomyces and Saccharomyces yeasts in wine fermentation was reviewed. A particular focus will be reserved on molecular studies regarding the role of nutrients, the production of the main byproducts and volatile compounds, ethanol reduction, and antagonistic actions for biological control in mixed fermentations.

Enzymes as a Reservoir of Host Defence Peptides

Host defence peptides (HDPs) are powerful modulators of cellular responses to various types of insults caused by pathogen agents. To date, a wide range of HDPs, from species of different kingdoms including bacteria, plant and animal with extreme diversity in structure and biological activity, have been described. Apart from a limited number of peptides ribosomally synthesized, a large number of promising and multifunctional HDPs have been identified within protein precursors, with properties not necessarily related to innate immunity, consolidating the fascinating hypothesis that proteins have a second or even multiple biological mission in the form of one or more bio-active peptides. Among these precursors, enzymes constitute certainly an interesting group, because most of them are mainly globular and characterized by a fine specific internal structure closely related to their catalytic properties and also because they are yet little considered as potential HDP releasing proteins. In this regard, the main aim of the present review is to describe a panel of HDPs, identified in all canonical classes of enzymes, and to provide a detailed description on hydrolases and their corresponding HDPs, as there seems to exist a striking link between these structurally sophisticated catalysts and their high content in cationic and amphipathic cryptic peptides.

Live Bacterial Prophylactics in Modern Poultry

Commercial poultry farms frequently use live bacterial prophylactics like vaccines and probiotics to prevent bacterial infections. Due to the emergence of antibiotic-resistant bacteria in poultry animals, a closer examination into the health benefits and limitations of commercial, live prophylactics as an alternative to antibiotics is urgently needed. In this review, we summarize the peer-reviewed literature of several commercial live bacterial vaccines and probiotics. Per our estimation, there is a paucity of peer-reviewed published research regarding these products, making repeatability, product-comparison, and understanding biological mechanisms difficult. Furthermore, we briefly-outline significant issues such as probiotic-label accuracy, lack of commercially available live bacterial vaccines for major poultry-related bacteria such as Campylobacter and Clostridium perfringens, as well research gaps (i.e., probiotic-mediated vaccine adjuvancy, gut-brain-microbiota axis). Increased emphasis on these areas would open several avenues for research, ranging from improving protection against bacterial pathogens to using these prophylactics to modulate animal behavior.

Metabolic Engineering of Wine Strains of Saccharomyces cerevisiae

Modern industrial winemaking is based on the use of starter cultures of specialized wine strains of Saccharomyces cerevisiae yeast. Commercial wine strains have a number of advantages over natural isolates, and it is their use that guarantees the stability and reproducibility of industrial winemaking technologies. For the highly competitive wine market with new demands for improved wine quality, it has become increasingly critical to develop new wine strains and winemaking technologies. Novel opportunities for precise wine strain engineering based on detailed knowledge of the molecular nature of a particular trait or phenotype have recently emerged due to the rapid progress in genomic and "postgenomic" studies with wine yeast strains. The review summarizes the current achievements of the metabolic engineering of wine yeast, the results of recent studies and the prospects for the application of genomic editing technologies for improving wine S. cerevisiae strains.

Effect of Candida intermedia LAMAP1790 Antimicrobial Peptides against Wine-Spoilage Yeasts Brettanomyces bruxellensis and Pichia guilliermondii

Wine spoilage yeasts are one of the main issues in the winemaking industry, and the control of the Brettanomyces and Pichia genus is an important goal to reduce economic loses from undesired aromatic profiles. Previous studies have demonstrated that Candida intermedia LAMAP1790 produces antimicrobial peptides of molecular mass under 10 kDa with fungicide activity against Brettanomyces bruxellensis, without affecting the yeast Saccharomyces cerevisiae. So far, it has not been determined whether these peptides show biocontroller effect in this yeast or other spoilage yeasts, such as Pichia guilliermondii. In this work, we determined that the exposure of B. bruxellensis to the low-mass peptides contained in the culture supernatant of C. intermedia LAMAP1790 produces a continuous rise of reactive oxygen species (ROS) in this yeast, without presenting a significant effect on membrane damage. These observations can give an approach to the antifungal mechanism. In addition, we described a fungicide activity of these peptides fraction against two strains of P. guilliermondii in a laboratory medium. However, carrying out assays on synthetic must, peptides must show an effect on the growth of B. bruxellensis. Moreover, these results can be considered as a start to develop new strategies for the biocontrol of spoilage yeast.

Diversity of Oligopeptide Transport in Yeast and Its Impact on Adaptation to Winemaking Conditions

Nitrogen is an essential nutrient for yeasts and its relative abundance is an important modulator of fermentation kinetics. The main sources of nitrogen in food are ammonium and free amino acids, however, secondary sources such as oligopeptides are also important contributors to the nitrogen supply. In yeast, oligopeptide uptake is driven by different families of proton–coupled transporters whose specificity depends on peptide length. Proton-dependent Oligopeptide Transporters (POT) are specific to di- and tri-peptides, whereas the Oligopeptide Transport (OPT) family members import tetra- and pentapeptides. Recently, the novel family of Fungal Oligopeptide Transporters (FOT) has been identified in Saccharomyces cerevisiae wine strains as a result of a horizontal gene transfer from Torulaspora microellipsoides. In natural grape must fermentations with S. cerevisiae, Fots have a broader range of oligopeptide utilization in comparison with non-Fot strains, leading to higher biomass production and better fermentation efficiency. In this review we present the current knowledge on the diversity of oligopeptide transporters in yeast, also discussing how the consumption of oligopeptides provides an adaptive advantage to yeasts within the wine environment.

Yeast-Yeast Interactions: Mechanisms, Methodologies and Impact on Composition

During the winemaking process, alcoholic fermentation is carried out by a consortium of yeasts in which interactions occurs. The consequences of these interactions on the wine matrix have been widely described for several years with the aim of controlling the winemaking process as well as possible. In this review, we highlight the wide diversity of methodologies used to study these interactions, and their underlying mechanisms and consequences on the final wine composition and characteristics. The wide variety of matrix parameters, yeast couples, and culture conditions have led to contradictions between the results of the different studies considered. More recent aspects of modifications in the composition of the matrix are addressed through different approaches that have not been synthesized recently. Non-volatile and volatile metabolomics, as well as sensory analysis approaches are developed in this paper. The description of the matrix composition modification does not appear sufficient to explain interaction mechanisms, making it vital to take an integrated approach to draw definite conclusions on them.

The Sensory Quality Improvement of Citrus Wine through Co-Fermentations with Selected Non-Saccharomyces Yeast Strains and Saccharomyces cerevisiae

Co-fermentation of selected non-Saccharomyces yeast strain with Saccharomyces cerevisiae is regarded as a promising approach to improve the sensory quality of fruit wine. To evaluate the effects of co-fermentations between the selected non-Saccharomyces yeast strains (Hanseniaspora opuntiae, Hanseniaspora uvarum and Torulaspora delbrueckii) and S. cerevisiae on the sensory quality of citrus wine, the fermentation processes, the chemical compositions, and the sensory evaluations of citrus wines were analyzed. Compared with those of S. cerevisiae fermentation, co-fermentations produced high sensory qualities, and S. cerevisiae/H. opuntiae co-fermentation had the best sensory quality followed by Sc-Hu and Sc-Td co-fermentations. Additionally, all the co-fermentations had a lower amount of ethanol and total acidity, higher pH value, and higher content of volatile aroma compounds, especially the content of higher alcohol and ester compounds, than those of S. cerevisiae fermentation. Therefore, co-fermentations of the non-Saccharomyces yeast strains and S. cerevisiae could be employed to improve the sensory quality of citrus wines. These results would provide not only methods to improve the sensory quality of citrus wine, but also a valuable reference for the selection of non-Saccharomyces yeast strains for fruit wine fermentation.

Proteomics insights into the responses of Saccharomyces cerevisiae during mixed-culture alcoholic fermentation with Lachancea thermotolerans

The response of Saccharomyces cerevisiae to cocultivation with Lachancea thermotolerans during alcoholic fermentations has been investigated using tandem mass tag (TMT)-based proteomics. At two key time-points, S. cerevisiae was sorted from single S. cerevisiae fermentations and from mixed fermentations using flow cytometry sorting. Results showed that the purity of sorted S. cerevisiae was above 96% throughout the whole mixed-culture fermentation, thereby validating our sorting methodology. By comparing protein expression of S. cerevisiae with and without L. thermotolerans, 26 proteins were identified as significantly regulated proteins at the early death phase (T1), and 32 significantly regulated proteins were identified at the late death phase (T2) of L. thermotolerans in mixed cultures. At T1, proteins involved in endocytosis, increasing nutrient availability, cell rescue and resistance to stresses were upregulated, and proteins involved in proline synthesis and apoptosis were downregulated. At T2, proteins involved in protein synthesis and stress responses were up- and downregulated, respectively. These data indicate that S. cerevisiae was stressed by the presence of L. thermotolerans at T1, using both defensive and fighting strategies to keep itself in a dominant position, and that it at T2 was relieved from stress, perhaps increasing its enzymatic machinery to ensure better survival.

Mechanism of antimicrobial peptide NP-6 from Sichuan pepper seeds against E. coli and effects of different environmental factors on its activity

A novel antimicrobial peptide named NP-6 was identified in our previous work. Here, the mechanisms of the peptide against Escherichia coli (E. coli) were further investigated, as well as the peptide's resistance to temperature, pH, salinity, and enzymes. The transmission electron microscopy (TEM), confocal laser scanning microcopy (CLSM), and flow cytometric (FCM) analysis, combined with measurement of released K⁺, were performed to evaluate the effect of NP-6 E. coli cell membrane. The influence of NP-6 on bacterial DNA/RNA and enzyme was also investigated. The leakage of K⁺ demonstrated that NP-6 could increase the permeability of E. coli cell membrane. The ATP leakage, FCM, and CLSM assays suggested that NP-6 caused the disintegration of bacterial cell membrane. The TEM observation indicated that NP-6 could cause the formation of empty cells and debris. Besides, the DNA-binding assay indicated that NP-6 could bind with bacterial genomic DNA in a way that ethidium bromide (EB) did, and suppress the migration of DNA/RNA in gel retardation. Additionally, NP-6 could also affect the activity of β-galactosidase. Finally, the effect of different surroundings such as heating, pH, ions, and protease on the antimicrobial activity of NP-6 against E. coli was also investigated. Results showed that the peptide was heat stable in the range of 60~100 °C and performed well at pH 6.0~8.0. However, the antimicrobial activity of NP-6 decreased significantly in the presence of Mg²⁺/Ca²⁺, and after incubation with trypsin/proteinase K. The results will provide a theoretical support in the further application of NP-6.

Dominance of wine Saccharomyces cerevisiae strains over S. kudriavzevii in industrial fermentation competitions is related to an acceleration of nutrient uptake and utilization

Grape must is a sugar-rich habitat for a complex microbiota which is replaced by Saccharomyces cerevisiae strains during the first fermentation stages. Interest on yeast competitive interactions has recently been propelled due to the use of alternative yeasts in the wine industry to respond to new market demands. The main issue resides in the persistence of these yeasts due to the specific competitive activity of S. cerevisiae. To gather deeper knowledge of the molecular mechanisms involved, we performed a comparative transcriptomic analysis during fermentation carried out by a wine S. cerevisiae strain and a strain representative of the cryophilic S. kudriavzevii, which exhibits high genetic and physiological similarities to S. cerevisiae, but also differences of biotechnological interest. In this study, we report that transcriptomic response to the presence of a competitor is stronger in S. cerevisiae than in S. kudriavzevii. Our results demonstrate that a wine S. cerevisiae industrial strain accelerates nutrient uptake and utilization to outcompete the co-inoculated yeast, and that this process requires cell-to-cell contact to occur. Finally, we propose that this competitive phenotype evolved recently, during the adaptation of S. cerevisiae to man-manipulated fermentative environments, since a non-wine S. cerevisiae strain, isolated from a North American oak, showed a remarkable low response to competition.

A Control Alternative for the Hidden Enemy in the Wine Cellar

Brettanomyces bruxellensis has been described as the principal spoilage yeast in the winemaking industry. To avoid its growth, wine is supplemented with SO2, which has been questioned due to its potential harm to health. For this reason, studies are being focused on searching for, ideally, natural new antifungals. On the other hand, it is known that in wine production there are a variety of microorganisms, such as yeasts and bacteria, that are possible biological controls. Thus, it has been described that some microorganisms produce antimicrobial peptides, which might control yeast and bacteria populations. Our laboratory has described the Candida intermedia LAMAP1790 strain as a natural producer of antimicrobial compounds against food spoilage microorganisms, as is B. bruxellensis, without affecting the growth of S. cerevisiae. We have demonstrated the proteinaceous nature of the antimicrobial compound and its low molecular mass (under 10 kDa). This is the first step to the possible use of C. intermedia as a selective bio-controller of the contaminant yeast in the winemaking industry.

Biocontrol of Brettanomyces/Dekkera bruxellensis in alcoholic fermentations using saccharomycin-overproducing Saccharomyces cerevisiae strains

Microbial contamination of alcoholic fermentation processes (e.g. winemaking and fuel-ethanol production) is a serious problem for the industry since it may render the product unacceptable and/or reduce its productivity, leading to large economic losses. Brettanomyces/Dekkera bruxellensis is one of the most dangerous microbial contaminant of ethanol industrial fermentations. In the case of wine, this yeast species can produce phenolic compounds that confer off-flavours to the final product. In fuel-ethanol fermentations, D. bruxellensis is a persistent contaminant that affects ethanol yields and productivities. We recently found that Saccharomyces cerevisiae secretes a biocide, which we named saccharomycin, composed of antimicrobial peptides (AMPs) derived from the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Saccharomycin is active against several wine-related yeast species, namely D. bruxellensis. However, the levels of saccharomycin naturally secreted by S. cerevisiae during alcoholic fermentation are not sufficient to ensure the complete death of D. bruxellensis. Therefore, the aim of the present work was to construct genetically modified S. cerevisiae strains to overproduce these GAPDH-derived AMPs. The expression levels of the nucleotides sequences encoding the AMPs were evaluated in the modified S. cerevisiae strains by RT-qPCR, confirming the success of the recombinant approach. Furthermore, we confirmed by immunological tests that the modified S. cerevisiae strains secreted higher amounts of the AMPs by comparison with the non-modified strain, inducing total death of D. bruxellensis during alcoholic fermentations.

Improving Ethyl Acetate Production in Baijiu Manufacture by Wickerhamomyces anomalus and Saccharomyces cerevisiae Mixed Culture Fermentations

Ethyl acetate content has strong influence on the style and quality of Baijiu. Therefore, this study investigated the effect of Saccharomyces cerevisiae Y3401 on the production of ethyl acetate by Wickerhamomyces anomalus Y3604. Analysis of cell growth showed that Y3401 influences Y3604 by nutrient competition and inhibition by metabolites, while the effect of Y3604 on Y3401 was mainly competition for nutrients. Mixed fermentation with two yeasts was found to produce more ethyl acetate than a single fermentation. The highest yield of ethyl acetate was 2.99 g/L when the inoculation ratio of Y3401:Y3604 was 1:2. Synergistic fermentation of both yeasts improved ethyl acetate production and increased the content of other flavor compounds in liquid and simulated solid-state fermentation for Baijiu. Saccharomyces cerevisiae had a positive effect on ethyl acetate production in mixed culture and provides opportunities to alter the aroma and flavor perception of Baijiu.

Investigating the Effect of Selected Non-Saccharomyces Species on Wine Ecosystem Function and Major Volatiles

Natural alcoholic fermentation is initiated by a diverse population of several non-Saccharomyces yeast species. However, most of the species progressively die off, leaving only a few strongly fermentative species, mainly Saccharomyces cerevisiae. The relative performance of each yeast species is dependent on its fermentation capacity, initial cell density, ecological interactions as well as tolerance to environmental factors. However, the fundamental rules underlying the working of the wine ecosystem are not fully understood. Here we use variation in cell density as a tool to evaluate the impact of individual non-Saccharomyces wine yeast species on fermentation kinetics and population dynamics of a multi-species yeast consortium in synthetic grape juice fermentation. Furthermore, the impact of individual species on aromatic properties of wine was investigated, using Gas Chromatography-Flame Ionization Detector. Fermentation kinetics was affected by the inoculation treatment. The results show that some non-Saccharomyces species support or inhibit the growth of other non-Saccharomyces species in the multi-species consortium. Overall, the fermentation inoculated with a high cell density of Starmerella bacillaris displayed the fastest fermentation kinetics while fermentation inoculated with Hanseniaspora vineae showed the slowest kinetics. The production of major volatiles was strongly affected by the treatments, and the aromatic signature could in some cases be linked to specific non-Saccharomyces species. In particular, Wickerhamomyces anomalus at high cell density contributed to elevated levels of 2-Phenylethan-1-ol whereas Starm. bacillaris at high cell density resulted in the high production of 2-methylpropanoic acid and 3-Hydroxybutanone. The data revealed possible direct and indirect influences of individual non-Saccharomyces species within a complex consortium, on wine chemical composition.

Novel antimicrobial peptides produced by Candida intermedia LAMAP1790 active against the wine-spoilage yeast Brettanomyces bruxellensis

Brettanomyces bruxellensis negatively impacts on the sensorial quality of wine by producing phenolic compounds associated with unpleasant odors. Thus, the control of this spoilage yeast is a critical factor during the winemaking process. A recent approach used to biocontrol undesired microorganisms is the use of yeast released antimicrobial peptides (AMPs), but this strategy has been poorly applied to wine-related microorganisms. The aim of this study was to evaluate the antifungal capacity of Candida intermedia LAMAP1790 against wine-spoilage strains of B. bruxellensis and fermentative strains of Saccharomyces cerevisiae, and also to determine the chemical nature of the compound. The exposure of strains to the supernatant of C. intermedia saturated cultures showed antifungal activity against B. bruxellensis, without affecting the growth of S. cerevisiae. By fractionation and concentration of C. intermedia supernatants, it was determined that the antifungal activity was related to the presence of heat-labile peptides with molecular masses under 5 kDa. To our knowledge, this is the first report of AMPs secreted by C. intermedia that control B. bruxellensis. This could lead to the development of new biocontrol strategies against this wine-spoilage yeast.

The Use of Mixed Populations of Saccharomyces cerevisiae and S. kudriavzevii to Reduce Ethanol Content in Wine: Limited Aeration, Inoculum Proportions, and Sequential Inoculation

Saccharomyces cerevisiae is the most widespread microorganism responsible for wine alcoholic fermentation. Nevertheless, the wine industry is currently facing new challenges, some of them associate with climate change, which have a negative effect on ethanol content and wine quality. Numerous and varied strategies have been carried out to overcome these concerns. From a biotechnological point of view, the use of alternative non-Saccharomyces yeasts, yielding lower ethanol concentrations and sometimes giving rise to new and interesting aroma, is one of the trendiest approaches. However, S. cerevisiae usually outcompetes other Saccharomyces species due to its better adaptation to the fermentative environment. For this reason, we studied for the first time the use of a Saccharomyces kudriavzevii strain, CR85, for co-inoculations at increasing proportions and sequential inoculations, as well as the effect of aeration, to improve its fermentation performance in order to obtain wines with an ethanol yield reduction. An enhanced competitive performance of S. kudriavzevii CR85 was observed when it represented 90% of the cells present in the inoculum. Furthermore, airflow supply of 20 VVH to the fermentation synergistically improved CR85 endurance and, interestingly, a significant ethanol concentration reduction was achieved.