Yeast Populations Research Articles

Study of grape microorganisms in Moldovan vineyards: influence of human and natural factors

The objective of this study was to investigate the microbial diversity on the grape berries under different climate conditions. Sixteen samples from ten vineyards were taken from three PGI regions in Republic of Moldova Moldova during years 2018–2020. The year of harvest had a significant effect on the amount of yeasts, but the geographical location did not significantly influence this criterion. As natural factors, the influence of temperature and precipitation during both the growing season and the month of grape harvest was studied. The selected methods for vineyard plant protection were as follows: fungicides to control powdery mildew, fungicides to control mange and insecticides. The total yeast population per grape ranged from 3.8E+04 to 2.3E+07 CFU/berry and the culturable yeast population ranged from 1.7E+03 to 8.0E+06. The harvest month temperature affects the yeast population the most, fungicide use in mealybug control reduces the culturable yeast population but increases the total yeast population; insecticide treatment only increases the total yeast population but has no impact on culturable yeasts.In addition, six species yeast have been identified: A.pullulans, M.pulcherrima, H. uvarum, R. Glutinmis, R. graminis and S.cerevisiae. The Saccharomyces cerevisiae strain isolated from the 2020 crop is totally different from the 2018 and 2019 crops. The bacteria population is at a low level, except for a few samples, P. damnosus, L. brevis, L.fermentum, G. oxydants were isolated.

Effect of Three Different Preservatives on the Microbiota of Shalgam, a Traditional Lactic Acid Fermented Beverage.

Shalgam is a traditional Turkish beverage derived from the natural fermentation of purple carrots (Daucus carota) that boasts valuable antioxidant and prebiotic properties. These features of shalgam increase efforts to enhance its shelf life and ensure safe consumption. In this study, the effects of three different preservatives (sodium benzoate, potassium sorbate, or natamycin) on the physicochemical and microbiological properties of shalgam produced at laboratory scale and stored at room temperature for six months were investigated. Each preservative was used in four different concentrations (25, 100, 400, and 800 mg/L) to assess their impacts on the population of lactic acid bacteria (LAB) and yeast. After determining the total acidity and pH of the samples, colorimetric measurements were performed. The isolated LAB were defined using the matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF/TOF MS) method. The addition of preservatives did not significantly affect the pH of the shalgam samples (3.44-3.52) compared to the control sample (3.43). However, a slight increase was observed in the total acidity of preservative-treated samples, with the highest level (5.61 g/L lactic acid) recorded in samples containing 100 mg/L sodium benzoate. Lacticaseibacillus paracasei subsp. paracasei, which has the potential to impart probiotic properties to shalgam, was the predominant LAB species in both non-treated and preservative-treated samples. The use of preservatives significantly reduced the total number of yeasts, which may cause spoilage in shalgam. The results indicate that using sodium benzoate at a concentration of 100 mg/L is the optimum method for shalgam production, resulting in the highest total acidity value obtained. Overall, the findings provide a significant contribution to prolonging the shelf life of shalgam, a beverage with immense production and consumption potential worldwide.

Effects of different irradiation doses and storage period on microbiological characteristics of wheat (Triticum aestivum L.)

Microbiological analysis of wheat (Triticum aestivum L.) treated with different doses of ionizing radiation (0.2 kGy, 0.5 kGy, 1 kGy, 5 kGy and 10 kGy) is presented in this paper. The aim was to determine the influence of different irradiation doses on the microbial population profile of wheat. In all samples, the total bacterial count and the populations of Enterobacteriaceae, Escherichia coli, Salmonella spp, coagulase-positive Staphylococci, Pseudomonas aeruginosa, Bacillus cereus, Clostridium perfringens, yeasts and molds were examined. The analyses were carried out twice: immediately after irradiation and nine months after treatment. Obtained results revealed the presence of Bacillus cereus, Enterobacteriaceae, yeasts and molds in all examined samples. Salmonella spp, Pseudomonas aeruginosa, Escherichia coli and Clostridium perfringens, were not detected. It has been found that the number of microorganisms decreases with the increase in the irradiation dose, with no viable microorganisms detected at the dose of 10 kGy. In all examined samples, nine months after irradiation, there was a noticeable reduction in the number of microorganisms. Only yeasts and molds were detected at a dose of 5 kGy, while no microbial growth was observed at 10 kGy. There are no reference studies on Enterobacteriaceae inactivation in wheat by ionizing radiation and storage. Therefore this study is the first contribution to understanding this microbial community decrease by gamma radiation after room temperature storage. The results highlighted the prolonged effect of ionizing radiation treatment on the microbiological safety of wheat.

Metagenomic analysis of the microbial community in kefir grains from different milk sources

Abstract. Sumarmono J, Kusuma RJ, Rahayu N, Sukarno AS, Wulansari PD. 2023. Metagenomic analysis of the microbial community in kefir grains from different milk sources. Biodiversitas 24: 5302-5308. Kefir is a type of traditional fermented milk made from kefir grains. The quality of kefir grain depends on the milk medium, which impacts microbial diversity and population. This study uses metagenomic analysis to assess the microbial populations of kefir grains prepared from cow's milk and goat milk using the 16s rRNA method. The results revealed that >99% Relative Abundance (RA) of the sample's total bacteria belonged to the phylum Firmicutes and the phylum Bacteroidota, respectively. However, most of the phylum Firmicutes was found in the sample of goat milk kefir. Further investigation revealed that goat milk samples had Lactobacillus, Streptococcus, and Staphylococcus genera, while the cow milk samples contained >99% RA of Lactobacillus, Bacteroides, and Muribaculaceae. Regarding yeast, the family Saccharomycetaceae predominated in cow's milk, while goat milk had 2% of the family Saccharomycetaceae and 97% of unassigned microorganisms. The functional analysis revealed that kefir grains from the two sources had a variety of amino acid metabolisms, secondary metabolite metabolisms, and vitamin production. This metagenomic analysis shows that the type of milk affects the diversity of the population of both bacteria and yeast. This study opens up opportunities to further investigate the potential of kefir as a functional food beverage, a source of probiotics, and an antibacterial agent property.

Do regrowth age and microbial inoculant usage affect the microbial diversity and fermentation characteristics of forage peanut silage?

AbstractThis study evaluated the fermentation characteristics, microbial diversity, chemical composition, and in vitro digestibility of forage peanut silage harvested at two regrowth ages and treated with microbial inoculants at different fermentation periods. A randomized block design was used, with two regrowth ages (R; 40 and 80 days), three microbial inoculants (I; control without inoculant [CTRL], strain AV14.17—Lactiplantibacillus pentosus strain AV14.17 [ISO], and commercial inoculant [CI] Sil‐All 4 × 4 (Lallemand Animal Nutrition®, Patos de Minas‐MG, Brazil), and four storage time (ST; 3, 14, 30, and 60 days after ensiling) arranged in a 2 × 3 × 4 factorial scheme, with four replications. The R × I × ST interaction had a significant effect (p ≤ .05) on the ammoniacal nitrogen content in relation to total nitrogen (NH3‐N/ total N) and on the yeast population. The I × ST interaction also had a significant effect (p ≤ .05) on pH, soluble carbohydrate, NH3‐N/total N, lactic acid bacteria, yeast, and filamentous fungi. Inoculated silages with ISO and CI showed lower pH and NH3‐N/total N values, as well as lower abundance of enterobacteria, yeast, and filamentous fungi. In silages inoculated with ISO, the relative abundance of genus Lactiplantibacillus was high and that of genus Enterobacter was low. Silages inoculated with ISO and CI showed predominance of the family Lactobacillaceae. The data support the recommendation to ensile forage peanut at both regrowth ages (40 and 80 days) associated with microbial inoculant application to promote improvements in the fermentation characteristics of the silage and a greater abundance of genus Lactiplantibacillus.

Performance of Okra and Soil Using Indigenous Microorganisms Inoculants

Microbial inoculants are beneficial microorganisms applied to plants or the soil to promote plant growth and control pest disease and weeds. Microbial inoculants isolated from local surroundings are indigenous microorganisms (IMO) inoculants. The performance of the IMO inoculants is varied depending on the sources and the local environment. Therefore, it is important to identify the right sources to enhance the efficiency of the IMO inoculants. This research aims to study the performance of okra and soil by mixing potential yeast sources for indigenous microorganisms (IMO) inoculants. Longan and mango were chosen as the sources of yeasts. The IMO inoculants were fermented for a week, and the microorganisms group was identified. Then, the IMO inoculants were applied to the okra and tested for physical and mineral content analysis. IMO inoculants with mango and longan showed a higher yeast population than the control. However, IMO inoculants with mango showed the best plant growth and harvesting time performance. The soil treated with both IMO inoculants also showed higher potassium and calcium. To conclude, plants treated with both IMO inoculants performed better than the control. Thus, IMO inoculants with longan and mango may potentially enhance the yeast community in IMO inoculants, indirectly improving okra growth and benefiting the agriculture field in the future.

Evolution of haploid and diploid populations reveals common, strong, and variable pleiotropic effects in non-home environments.

Adaptation is driven by the selection for beneficial mutations that provide a fitness advantage in the specific environment in which a population is evolving. However, environments are rarely constant or predictable. When an organism well adapted to one environment finds itself in another, pleiotropic effects of mutations that made it well adapted to its former environment will affect its success. To better understand such pleiotropic effects, we evolved both haploid and diploid barcoded budding yeast populations in multiple environments, isolated adaptive clones, and then determined the fitness effects of adaptive mutations in 'non-home' environments in which they were not selected. We find that pleiotropy is common, with most adaptive evolved lineages showing fitness effects in non-home environments. Consistent with other studies, we find that these pleiotropic effects are unpredictable: they are beneficial in some environments and deleterious in others. However, we do find that lineages with adaptive mutations in the same genes tend to show similar pleiotropic effects. We also find that ploidy influences the observed adaptive mutational spectra in a condition-specific fashion. In some conditions, haploids and diploids are selected with adaptive mutations in identical genes, while in others they accumulate mutations in almost completely disjoint sets of genes.

Wine aroma modification by Hanseniaspora uvarum: A multiple-step strategy for screening potential mixed starters

Hanseniaspora uvarum is a prevalent yeast species in vineyards. However, its application in grape wine fermentation remains limited. This study used culture-dependent and -independent approaches to investigate the dynamics of H. uvarum during the spontaneous fermentation of Cabernet Sauvignon grapes. The results revealed that H. uvarum constituted 77.49 % of the non-Saccharomyces yeast population during fermentation. An indigenous strain, QTX-C10, was isolated from the 148 H. uvarum strains using a multistep screening strategy. The 1:1 co-inoculation of QTX-C10 with Saccharomyces cerevisiae proved to be an optimal strategy for mixed fermentation, resulting in a 48.54 %–59.55 % increase in ethyl esters in Cabernet Sauvignon wine and a 96.94 %–110.92 % increase in Chardonnay wine. Furthermore, this approach reduced the acetic acid levels by 12.50 %–17.07 % for Cabernet Sauvignon wine and 10.81 %–17.78 % for Chardonnay wine. Additionally, increased ethyl ester content may enhance the tropical fruit flavor of Cabernet Sauvignon wines.

Rapid evolution of pre-zygotic reproductive barriers in allopatric populations.

Adaptive divergence leading to speciation is the major evolutionary process generating diversity in life forms. The most commonly observed form of speciation is allopatric speciation which requires that gene flow be prevented between populations by physical or temporal barriers, as they adapt to their respective environments. Eventually, these adaptive responses lead to accumulation of mutations in different lines. The increased genetic distance between the lines is known to lead to the populations becoming reproductively isolated. A widely accepted theory is that speciation simply occurs as a by-product of adaptive response of the populations. Several examples of allopatric speciation from ecology and laboratory exist. However, we know little about the nature (pre- or post-zygotic) of barriers that arise first in this process. Understanding the first barriers that arise between populations is key to understanding how the process of speciation initiates. In recent years, fungi have been used as model organisms to answer questions related to the evolution of reproductive isolation. Here, we show rapid evolution of pre-zygotic barriers between allopatric yeast populations. We further demonstrate that these pre-zygotic barriers arise due to altered mating kinetics of the evolved population. Moreover, our non-adaptive evolution experiments with yeast under limited selection pressure also show rapid emergence of reproductive isolation. Overall, our results show that evolution of pre-zygotic reproductive barriers can occur as a result of natural selection or drift.IMPORTANCEA population diversifies into two or more species-such a process is known as speciation. In sexually reproducing microorganisms, which barriers arise first-pre-mating or post-mating? In this work, we quantify the relative strengths of these barriers and demonstrate that pre-mating barriers arise first in allopatrically evolving populations of yeast, Saccharomyces cerevisiae. These defects arise because of the altered kinetics of mating of the participating groups. Thus, our work provides an understanding of how adaptive changes can lead to diversification among microbial populations.

Non-Saccharomyces Yeasts from Organic Vineyards as Spontaneous Fermentation Agents.

Currently, non-Saccharomyces yeasts are the subject of interest, among other things, for their contribution to the aromatic complexity of wines. In this study, the characterisation of non-Saccharomyces yeasts was addressed by their isolation during spontaneous fermentations of organic Verdejo grapes, obtaining a total of 484 isolates, of which 11% were identified by molecular techniques as non-Saccharomyces yeasts. Fermentative isolates belonging to the species Hanseniaspora meyeri, Hanseniaspora osmophila, Pichia guilliermondii, Pichia kudriavzevii, Torulaspora delbrueckii, and Wickerhamomyces anomalus were analysed. Significant differences were found in the yeast populations established at the different fermentation stages. Interestingly, W. anomalus stood up as a widely distributed species in vineyards, vintages, and fermentation stages. Several of the strains studied stood out for their biotechnological potential in the production of Verdejo wine, showing the presence of relevant enzymatic activity for the release of varietal aromas and the technological improvement of the winemaking process. Three enzymatic activities were found in an important number of isolates, β-glucosidase, protease, and β-lyase, implicated in the positive aromatic impact on this style of white wine. In that sense, all the isolates of W. anomalus presented those activities. T. delbrueckii isolates were highlighted for their significant β-lyase activity. In addition, T. delbrueckii was outlined because of its potential to achieve an elevated fermenting power, as well as the lack of lag phase. The results obtained highlight the importance of maintaining the microbial diversity that contributes to the production of wines with unique and distinctive characteristics of the production region.

Antibiofilm Effect of Curcumin on Saccharomyces boulardii during Beer Fermentation and Bottle Aging.

In a prior study, we elucidated the biofilm formation of Saccharomyces boulardii on glass surfaces during beer bottle aging. Here, we supplemented brewing wort with curcumin at 25 μg/mL concentration to mitigate S. boulardii biofilm and enhance beer's functional and sensory attributes. An assessment encompassing biofilm growth and development, fermentation performance, FLO gene expression, yeast ultrastructure, bioactive content, and consumer acceptance of the beer was conducted throughout fermentation and aging. Crystal violet (CV) and XTT reduction assays unveiled a significant (p < 0.05) reduction in biofilm formation and development. Fluorescent staining (FITC-conA) and imaging with confocal laser scanning microscopy provided visual evidence regarding reduced exopolysaccharide content and biofilm thickness. Transcriptional analyses showed that key adhesins (FLO1, FLO5, FLO9, and FLO10) were downregulated, whereas FLO11 expression remained relatively stable. Although there were initial variations in terms of yeast population and fermentation performance, by day 6, the number of S. boulardii in the test group had almost reached the level of the control group (8.3 log CFU/mL) and remained stable thereafter. The supplementation of brewing wort with curcumin led to a significant (p < 0.05) increase in the beer's total phenolic and flavonoid content. In conclusion, curcumin shows promising potential for use as an additive in beer, offering potential antibiofilm and health benefits without compromising the beer's overall characteristics.

MIL-CELL: a tool for multi-scale simulation of yeast replication and prion transmission

The single-celled baker’s yeast, Saccharomyces cerevisiae, can sustain a number of amyloid-based prions, the three most prominent examples being [URE3], [PSI+], and [PIN+]. In the laboratory, haploid S. cerevisiae cells of a single mating type can acquire an amyloid prion in one of two ways (i) spontaneous nucleation of the prion within the yeast cell, and (ii) receipt via mother-to-daughter transmission during the cell division cycle. Similarly, prions can be lost due to (i) dissolution of the prion amyloid by its breakage into non-amyloid monomeric units, or (ii) preferential donation/retention of prions between the mother and daughter during cell division. Here we present a computational tool (Monitoring Induction and Loss of prions in Cells; MIL-CELL) for modelling these four general processes using a multiscale approach describing both spatial and kinetic aspects of the yeast life cycle and the amyloid-prion behavior. We describe the workings of the model, assumptions upon which it is based and some interesting simulation results pertaining to the wave-like spread of the epigenetic prion elements through the yeast population. MIL-CELL is provided as a stand-alone GUI executable program for free download with the paper. MIL-CELL is equipped with a relational database allowing all simulated properties to be searched, collated and graphed. Its ability to incorporate variation in heritable properties means MIL-CELL is also capable of simulating loss of the isogenic nature of a cell population over time. The capability to monitor both chronological and reproductive age also makes MIL-CELL potentially useful in studies of cell aging.

Total Mixed Ration Silages Based on Forage Cactus and Xerophile Legumes as Alternatives for Ruminants

This study aims to evaluate the fermentative profile, fermentative losses, microbial populations, aerobic stability, chemical composition, and in situ degradability of total mixed ration silages based on forage cactus associated with xerophytic legumes. The treatments consisted of four total mixed ration silages based on forage cactus and concentrate (TMRC), associated with legumes such as Gliricidia sepium (TMRG), Leucaena (TMRL), and Senna obtusifolia (TMRS). There was a significant difference (p &lt; 0.05) among the evaluated treatments for the pH and NH3-N (% of total N) variables. The pH values remained within the ideal range, from 4.2 to 4.4, and the NH3-N content ranged from 2.21 to 0.85%. The dry matter recovery for the evaluated treatments averaged 89%. The lactic acid bacteria (LAB) counts ranged from 5.0 to 6.3 log CFU/g among the evaluated silages, with TMRC presenting the lowest count at 5 log CFU/g in comparison with the total mixed ration silages associated with legume plants. All of the total mixed ration silages associated with legumes presented an average mold count of 3.3 log CFU/g. Yeast populations were observed only for TMRG at 5 log CFU/g. A higher aerobic stability was observed for TMRC, followed by TMRG and then TMRS. In conclusion, the total mixed ration silages associated with G. sepium and S. obtusifolia can be recommended based on their fermentation and nutritional value.

Diversity and probiotic characterisation of yeast isolates in the bovine gastrointestinal tract.

The use of yeasts as a feed supplement for cattle can promote animal development and performance. However, for the positive results to be consistent, strains with probiotic properties must be selected. The objective of this study was to isolate and identify yeasts present in the bovine feces and evaluate their probiotic potential together with strains previously isolated from the rumen (preliminary study). A total of 193 isolates were studied, including 139 isolates (19 species) from fecal samples from 11 different animals (Bos taurus and Bos indicus) and 54 strains previously isolated from rumen fluid (Bos taurus). The yeast population in the feces ranged from 3.51 to 4.99 log CFU/g, with Candida pararugosa being the most abundant (isolated from the feces of six samples analysed). Isolates were selected that had negative results in the safety tests (hemolytic activity, DNAse, and gelatinase) and had percentages greater than 35 and 70% for hydrophobicity and auto-aggregation, respectively. In addition, selected isolates had percentages greater than 77.7 and 74.7% for coaggregation with pathogenic strains of Escherichia coli and Clostridium perfringens, respectively. The isolates with percentage growth at 39°C greater than 64.6% and viability greater than 96.7% were selected for survival testing under bovine gastrointestinal conditions. After the tests, the seven best isolates were selected, belonging to the species Candida pararugosa (L60, CCMA 928 and CCMA 930) and Pichia kudriavzevii (L97, L100, CCMA904, CCMA 907). The selected isolates were exopolysaccharide producers. Based on the results of the evaluated properties, the seven selected isolates were classified as potential probiotics for cattle.

Cottonseed cake as nutritional additive for sorghum silages

ABSTRACT This study aimed to determine the optimal proportion of cottonseed cake (CSC) as an additive in sorghum silage to improve its chemical composition, fermentative profile, microbial populations, losses, dry matter recovery, and aerobic stability. Five treatments were evaluated, varying the inclusion of CSC at ensiling (0, 50, 100, 200, and 200 g kg−1 on fresh matter basis). The results showed that the inclusion of CSC significantly increased the content of dry matter, crude protein, and ether extract in the silages. Water-soluble carbohydrates, buffering capacity, and ammoniacal nitrogen exhibited a linear decrease with increasing CSC inclusion. The populations of lactic acid bacteria and moulds showed a quadratic response to CSC inclusion. The yeast population was completely inhibited with a minimum inclusion of 200 g kg−1 CSC. Aerobic stability and dry matter recovery showed a linear increase with CSC inclusion. These findings indicate that adding CSC to sorghum silage enhances its nutritive value, fermentative profile, dry matter recovery, and effectively inhibits yeast growth, which is recommended to include 200 g kg−1 of CSC for good cost-effectiveness.

Evaluating Fermentation Quality, Aerobic Stability, and Rumen-Degradation (In Situ) Characteristics of Various Protein-Based Total Mixed Rations.

The purpose of this experiment was to evaluate changes in fermentation quality, chemical composition, aerobic stability, anti-nutritional factors, and in situ disappearance characteristics of various protein-based total mixed rations. Soybean meal (control, non-fermented), fermented cottonseed meal (F-CSM), and fermented rapeseed meal (F-RSM) group were used to prepare the TMRs with corn, whole-plant corn silage, corn stalks, wheat bran, and premix. The test groups were inoculated at 50% moisture with Bacillus clausii and Saccharomyces cariocanus and stored aerobically for 60 h. The nylon-bag method was used to measure and study the rumen's nutrient degradation. The pH of all TMRs after 48 h of air exposure was below 4.8, whereas that of the F-CSM and control and F-RSM groups increased to 5.0 and >7.0, respectively. After 8 h of aerobic exposure, the temperatures of all groups significantly increased, and 56 h later, they were 2 °C higher than the surrounding air. The lactic acid concentration in the F-CSM and F-RSM groups increased after 12 h of aerobic exposure and then decreased. The acetic acid concentrations in the fermented groups decreased significantly with the increasing air-exposure time. The yeast population of the TMRs increased to more than 8.0 log10 CFU/g before 72 h of air exposure, followed by a decrease in the population (5.0 log10 CFU/g). After fermentation, the free gossypol (FG) concentration in F-CSM decreased by half and did not change significantly during the air-exposure period. Fermentation with probiotics also reduced the F-RSM's glucosinolate concentration, resulting in a more than 50% detoxification rate. Compared with the F-CSM and F-RSM groups, the effective degradation rates of nutrients in the control group were the lowest, and the dry matter (DM), crude protein (CP), natural detergent fiber (NDF), and acid detergent fiber (ADF) all degraded effectively at rates of 28.4%, 34.5%, 27.8%, and 22.8%, respectively. Fermentation with B. clausii and S. cariocanus could improve the fermentation quality and nutrient composition, decrease the anti-nutritional factor, and increase nutrient degradation of the TMR with cottonseed meal or rapeseed meal as the main protein source, thus achieving detoxification.

Pesticide Residues and Berry Microbiome after Ozonated Water Washing in Table Grape Storage.

Nowadays, different systems for reducing pesticides in table grapes are being tested at different production stages either in the field or in postharvest. The present study tested ozonated water treatments at the beginning of the cold storage of the Princess® seedless table grape variety to reduce the residue contents of some pesticides and to evaluate their effect on gray mold and the berry microbiome. An ozone generator capable of producing an ozone concentration ranging from 18 to 65 Nm3 was utilized for obtaining three ozone concentration levels in water: 3, 5 and 10 mg/L. Ozonated water was placed in a 70 L plastic box where 500 g grape samples closed in perforated plastic clamshell containers were immersed utilizing two washing times (5 and 10 min). Overall, six ozonated water treatments were tested. After the ozonated water treatments, all samples were stored for 30 days at 2 °C and 95% relative humidity to simulate commercial practices. The pesticide residue contents were determined before the ozonated water treatments (T0) and 30 days after the cold storage (T1). The treatments with ozonated water washing reduced the pesticide residues up to 100%, while the SO2 control treatment reduced the pesticide residues ranging from 20.7 to 60.7%. Using 3 mg/L ozonated water to wash grapes for 5 min represented the optimal degradation conditions for all of the analyzed pesticides, except for fludioxonil, which degraded better with a washing time of 10 min. The ozone treatments did not significantly reduce the gray mold and the fungal and bacterial microbiome, while a relevant reduction was observed in the yeast population.

The impact of the duration of wave treatment on the development of yeast populations

Introduction: The scientific literature does not contain research on the influence of monochromatic light treatment on the development of bottom-fermenting beer yeast populations.Purpose: An analysis of the literature data allowed us to suppose the possibility of activating the development of the beer yeast Saccharomyces cerevisiae population through preliminary treatment with light of visible spectrum wavelengths, providing technological and economic efficiency of such an impact method on a production scale.Materials and Methods: The object of research was the process of cultivating a population of bottom-fermenting beer yeast Saflager S-189 (Fermentis). The subject was the influence of preliminary treatment of the seed yeast with monochromatic light with a wavelength of 980 nm on this process. Its effectiveness was assessed by the weight loss of the cultivation medium, the increase in the total cell titre, the proportion of unviable and "fed" cells. A KFK-2 photoelectrocolorimeter was used as a source of monochromatic light with wavelengths of the visible range. Seeding of mediums and sample preparation for analysis were performed in a BAVnp-01-"Laminar-S."-1.2 antibacterial air medium box. The yeast's fermenting activity was assessed by the weight loss of the nutrient medium; the total cell titre was established by counting in a Goryaev's chamber; the percentage of unviable cells was determined using methylene blue dye; the percentage of "fed" yeast cells was established by staining glycogen with iodine solution.Results: Preliminary treatment of the seed yeast with monochromatic light (980 nm) allowed increasing the fermenting activity of bottom-fermenting beer yeast by 10-15% compared to the control, which is consistent with the results of other research groups concerning populations of microorganisms of other genera and species. The values of other determined indicators - the proportion of "fed" and unviable cells, the total yeast cell titre - in the experimental variants were at the level of those in the control samples or slightly inferior to them. Data on the influence of the duration of seed yeast irradiation for 60, 120 or 180 minutes on the listed controlled indicators are presented, and the authors express the opinion about the appropriateness of its conduction for 60 minutes.Conclusion: The principle possibility of activating the development of a population of bottom-fermenting beer yeast by preliminary treatment of seed yeast with light with a wavelength of 980 nm, which can give an economic effect on an industrial scale, is substantiated; the necessity of testing the technological method under study in conditions close to production ones, i.e., for brewing wort with an irradiated suspension of seed yeast, is noted.

Identification and biotechnological characterisation of yeast microbiota involved in spontaneous fermented wholegrain sourdoughs.

New strategies in the cereal-based industry has brought about the elaboration of new sourdoughs with better microbial stability and safety as well as nutritional value such as those based on wholegrain flours. This has led to an increasing interest in the selection of adapted yeasts for using them as new starters. Therefore, this study aimed to isolate, identify, and characterise diverse yeast strains from wholegrain spontaneous sourdoughs. Three wholegrain sourdoughs (wheat, rye, and oat) were fermented and monitored for 96 h. Minimum pH values ranged from 3.1 to 3.5 while maximum yeast counts were reached at 72 h. A total of 76 yeast isolates were identified by polymerase chain reaction random amplification of polymorphic DNA (PCR-RAPD) and catalogued in six different species by sequencing the internal transcribed spacer (ITS) region. The major species were Candida glabrata, Saccharomyces cerevisiae, Kazachstania unispora, and Wickerhamomyces anomalus. The studied kinetic parameters of the growth curves (λ, G, ODmax , and μmax ) and the fermentation capacity allowed to ascertain that 12 and 5 strains, respectively, were better than baker's yeast control. The fibre assimilation ability (cellulose, xylose, and β-glucan) was observed in the 27% of the strains and only four strains showed phytase activity. The yeast population in the three wholegrain sourdoughs were variable along the fermentation time. Genetic identification showed that strains and species presented a different trend for each sourdough although common species were determined (e.g., W. anomalus). Candida glabrata (4T1) and Saccharomyces cerevisiae (3A6) showed, respectively, better kinetics and impedance results than the positive control, while W. anomalus (C4) was notorious in fibre assimilation and phytase degradation. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Yeasts Inoculation Effect on Bacterial Development in Carbonic Maceration Wines Elaboration.

Carbonic maceration (CM) vinification is a very traditional method that allows saving energy without great equipment investment, obtaining high-quality wines. However, due to its particularities, CM winemaking implies a higher risk of microbial alteration. This work studies the evolution of bacterial population along carbonic maceration wines elaboration with and without yeast inoculation. In the same way, two strategies of yeast inoculation were studied: "pied de cuve" and Active Dry Yeasts (ADY) seed. For this purpose, three conditions were assayed: spontaneous fermentation (without inoculation), "pied de cuve" technology, and ADY inoculation. For each condition, two winemaking methods were compared: carbonic maceration and the standard method of destemming and crushing (DC). The bacterial evolution (lactic acid and acetic acid bacteria) was followed in different fermentation stages. Finally, the wines obtained were analysed (pH and volatile acidity). In the non-inoculated wines produced by CM, high development of the bacterial population was observed (counts of acetic acid bacteria around 4.3 log cfu/mL), and finished wines presented high values of volatile acidity (>1.5 g/L), which did not occur in the inoculated vinifications (counts of acetic acid bacteria around 1.5 log cfu/mL and 0.5 g/l of volatile acidity). Thus, the control of yeast population, as a "pied de cuve" as ADY seed, seems to be an effective tool to avoid bacterial alterations in CM vinifications.