Molecular analysis of cutaneous yeast isolates in the mycobiota of children with atopic dermatitis.

The skin of patients with atopic dermatitis (AD) has a greater diversity of mycobiota. An observational, prospective, cross-sectional, analytical, and comparative study was conducted involving 80 patients with AD Group (ADG) and 50 individuals without AD (wADG) in a tertiary hospital in Brazil. Skin scale samples were collected from the frontal, cervical, fossae cubital, and popliteal regions and identified using molecular biology techniques. The results showed that 47.5% of ADG had identified yeasts compared to 0% of wADG (P < .001). The yeasts Rhodotorula mucilaginosa and Candida parapsilosis were the most abundant. The probability of colonization increased with age, showing values of 40% at 60 months and 80% at 220 months (P = .09). The cervical region (12.5%) was colonized to the greatest extent. Our findings revealed that positive mycology was not more probable when the scoring of atopic dermatitis or eczema area and severity index value increased (P = .23 and .53, respectively). The results showed that the sex, age, and different population types directly affected the composition of the mycobiota in the population analyzed. A higher frequency of colonization and greater diversity of yeast species were detected in the cutaneous mycobiota of children with AD.

Atopic dermatitis (AD) is a skin disease that can be colonized by microorganisms. We evaluated patients with and without the disease and found a higher frequency of colonization by Rhodotorula mucilaginosa and Candida parapsilosis on the skin of children with AD.

Low microbial diversity, yeast prevalence, and nematode-trapping fungal presence in fungal colonization and leaf microbiome of Serjania erecta.

Medicinal plant microbiomes undergo selection due to secondary metabolite presence. Resident endophytic/epiphytic microorganisms directly influence plant's bioactive compound synthesis. Hypothesizing low microbial diversity in Serjania erecta leaves, we assessed leaf colonization by epiphytic and endophytic fungi. Given its traditional medicinal importance, we estimated diversity in the endophytic fungal microbiome. Analyses included scanning electron microscopy (SEM), isolation of cultivable species, and metagenomics. Epiphytic fungi interacted with S. erecta leaf tissues, horizontally transmitted via stomata/trichome bases, expressing traits for nematode trapping. Cultivable endophytic fungi, known for phytopathogenic habits, didn't induce dysbiosis symptoms. This study confirms low leaf microbiome diversity in S. erecta, with a tendency towards more fungal species, likely due to antibacterial secondary metabolite selection. The classification of Halicephalobus sp. sequence corroborated the presence of nematode eggs on the epidermal surface of S. erecta by SEM. In addition, we confirmed the presence of methanogenic archaea and a considerable number of methanotrophs of the genus Methylobacterium. The metagenomic study of endophytic fungi highlighted plant growth-promoting yeasts, mainly Malassezia, Leucosporidium, Meyerozyma, and Hannaella. Studying endophytic fungi and S. erecta microbiomes can elucidate their impact on beneficial bioactive compound production, on the other hand, it is possible that the bioactive compounds produced by this plant can recruit specific microorganisms, impacting the biological system.

Exploring xylose metabolism in non-conventional yeasts: kinetic characterization and product accumulation under different aeration conditions.

d-Xylose is a metabolizable carbon source for several non-Saccharomyces species, but not for native strains of S. cerevisiae. For the potential application of xylose-assimilating yeasts in biotechnological processes, a deeper understanding of pentose catabolism is needed. This work aimed to investigate the traits behind xylose utilization in diverse yeast species. The performance of 9 selected xylose-metabolizing yeast strains was evaluated and compared across 3 oxygenation conditions. Oxygenation diversely impacted growth, xylose consumption, and product accumulation. Xylose utilization by ethanol-producing species such as Spathaspora passalidarum and Scheffersomyces stipitis was less affected by oxygen restriction compared with other xylitol-accumulating species such as Meyerozyma guilliermondii, Naganishia liquefaciens, and Yamadazyma sp., for which increased aeration stimulated xylose assimilation considerably. Spathaspora passalidarum exhibited superior conversion of xylose to ethanol and showed the fastest growth and xylose consumption in all 3 conditions. By performing assays under identical conditions for all selected yeasts, we minimize bias in comparisons, providing valuable insight into xylose metabolism and facilitating the development of robust bioprocesses. ONE-SENTENCE SUMMARY: This work aims to expand the knowledge of xylose utilization in different yeast species, with a focus on how oxygenation impacts xylose assimilation.

Identification of microorganisms in wet coffee fermentation Coffea arabica Var Catimor and Castillo in Jardín, Antioquia-Colombia, using culture-dependent methods / Identificación de microorganismos en fermentación húmeda de café Coffea arabica Var Catimor y Castillo en Jardín, Antioquia-Colombia, usando métodos cultivo-dependientes

Background: Mild Colombian coffees are recognized worldwide for their high-quality coffee cup. However, there have been some failures in post-harvest practices, such as coffee grain fermentation. These failures could occasionally lead to defects and inconsistencies in quality products and economic losses for coffee farmers. In Colombia, one of the fermentation methods most used by coffee growers is wet fermentation, conducted by submerging the de-pulped coffee beans for enough time in water tanks to remove the mucilage. Objectives: We evaluated the effect of the water (g)/de-pulped coffee (g) ratio (I: 0/25, II: 10/25, III: 20/25) and final fermentation time (24, 48, and 72 hours) on the total number of microbial groups. We also identified microorganisms of interest as starter cultures. Methods: We used a completely randomized experimental design with two factors; the effect of the water (g)/de-pulped coffee (g) ratio (I: 0/25, II: 10/25, III: 20/25) and final fermentation time (24, 48, and 72 hours), for 9 treatments with two replicates. During the coffee fermentation (1,950 g), the pH and °Brix were monitored. Total counts of different microbial groups (mesophiles, coliforms, lactic-acid bacteria, acetic-acid bacteria, and yeasts) were performed. Various isolates of microorganisms of interest as starter cultures (lactic-acid bacteria and yeasts) were identified using molecular sequencing techniques. Results: 21 lactic-acid bacteria (LAB) isolates and 22 yeasts were obtained from the different mini-batch fermentation systems. The most abundant lactic-acid bacteria species found were Lactiplantibacillus plantarum (46%) and Levilactobacillus brevis (31%). Pichia kluivery (39%) and Torulaspora delbrueckii (22%) were the most abundant yeast species. Conclusion The studied factors did not have effect over the microorganism's development. The identified bacterial and yeasts species have potential as starter cultures for better-quality coffees and in fermentation-related applications.

Antecedentes: Los cafés suaves lavados colombianos son reconocidos a nivel mundial por su buena puntuación sensorial; sin embargo, se han detectado fallas en las prácticas de postcosecha, como lo es la fermentación de los granos de café. Dichas fallas pueden causar defectos y carecer de consistencia en la calidad del producto, ocasionando pérdidas económicas para los caficultores. En Colombia, uno de los métodos más usados por los caficultores es la fermentación húmeda, la cual consiste en sumergir los granos de café despulpado en tanques con agua por un período de tiempo que permita la remoción del mucílago. Objetivos: La presente investigación evaluó la incidencia que tienen la proporción agua/granos despulpados de café (I: 0/25, II: 10/25, III: 20/25) y el tiempo final de fermentación (24, 48 y 72 horas) en el recuento final de grupos microbianos. Por otra parte, se identificaron taxonómicamente microorganismos de interés para su uso como cultivos iniciadores. Métodos: Mini-lotes consistieron en café despulpado (1950 g) puesto en recipientes de plástico abiertos y sumergidos en agua. Se aplicó un diseño experimental completamente aleatorizado de dos factores (proporción agua/ granos de café despulpado y tiempo) a tres niveles, para un total de nueve tratamientos con dos replicas. Durante las fermentaciones de café (1,950 g), el pH y los grados ºBrix, fueron monitoreados. Se realizaron los recuentos totales de los diferentes grupos microbianos: mesófilos, coliformes, bacterias ácido-lácticas, bacterias ácido-acéticas y levaduras. Se identificaron molecularmente diferentes aislados con potencial para ser usados como cultivos iniciadores (bacterias ácido-lácticas y levaduras). Resultados: Los resultados obtenidos mostraron que no hubo diferencia estádisticamente significativa entre los tratamientos aplicados y el recuento final de microorganismos. Un total de 21 aislados de bacterias ácido-lácticas (BAL) y 22 levaduras lograron obtenerse a partir de los diferentes sistemas de fermentación en mini-lote. Las especies de bacterias ácido-lácticas con mayor porcentaje acorde a su identificación taxonómica, corresponden a Lactiplantibacillus plantarum (46%), Levilactobacillus brevis (31%). Las especies de levaduras con mayor porcentaje acorde a su identificación taxonómica corresponden a Pichia kluivery (39%) y Torulaspora delbrueckii (22%). Conclusión Los factores estudiados no afectaron el crecimiento de ninguno de los grupos microbianos presentes en la fermentacion del café. Las especies de microorganismos identificados tienen potencial para se usados como cultivos starter o en aplicaciones dentro de las ciencias de fermentación.

Effects of dietary yeast mannan-rich fraction supplementation on growth performance, intestinal morphology, and lymphoid tissue characteristics in weaned piglets challenged with Escherichia Coli F4.

We evaluated the effects of supplementing yeast mannan-reach-fraction on growth performance, jejunal morphology and lymphoid tissue characteristics in weaned piglets challenged with E. Coli F4. A total of 20 crossbred piglets were used. At weaning, piglets were assigned at random to one of four groups: piglets challenged and fed the basal diet supplemented with yeast mannan-rich fraction (C-MRF, n = 5); piglets challenged and fed the basal diet (C-BD, n = 5); piglets not challenged and fed the basal diet supplemented with yeast mannan-rich fraction (NC-MRF, n = 5), and piglets not challenged and fed the basal diet (NC-BD). Each dietary treatment had five replicates. On days 4, 5 and 10, piglets were orally challenged with 108 CFU/mL of E. Coli F4. C-MRF piglets had higher BW (p = 0.002; interactive effect) than C-BD piglets. C-MRF piglets had higher (p = 0.02; interactive effect) ADG in comparison with C-BD piglets. C-MRF piglets had higher (p = 0.04; interactive effect) ADFI than C-BD piglets. The diameter of lymphoid follicles was larger (p = 0.010; interactive effect) in the tonsils of C-MRF piglets than C-BD piglets. Lymphoid cells proliferation was greater in the mesenteric lymphnodes and ileum (p = 0.04 and p = 0.03, respectively) of C-MRF piglets. A reduction (p > 0.05) in E. Coli adherence in the ileum of piglets fed MRF was observed. In conclusion, the results of the present study demonstrate that dietary yeast mannan-rich fraction supplementation was effective in protecting weaned piglets against E. Coli F4 challenge.

Impact of different fermentation times on the microbiological, chemical, and sensorial profile of coffees processed by self-induced anaerobiosis fermentation.

Variation in fermentation time may be an essential alternative to provide coffee beverages with different and unique sensory profiles. This work investigated the microbiological, chemical, and sensory changes in coffees submitted to different fermentation durations (0, 24, 48, 72, and 96 h). Self-induced anaerobiosis fermentation (SIAF) was used, and two treatments were performed: spontaneous fermentation and inoculation with S. cerevisiae CCMA0543. Microbiological analyses were performed, and the permanence of the inoculum was monitored. Chromatography (sugars, organic acids, and volatile compounds) was analyzed, and sensory analysis (temporal dominance of sensations - TDS) was performed. A total of 228 isolates were identified during spontaneous fermentation. The dominant bacteria and yeasts were Leuconostoc mesenteroides, Lactiplantibacillus plantarum, Staphylococcus warneri, Bacillus sp., Torulaspora delbrueckii, Hanseniaspora uvarum, and Meyerozyma caribbica. High concentrations of citric (18.67 mg.g- 1) and succinic (5.04 mg.g- 1) acids were detected at 96 h in SIAF fermentation. One hundred twenty-one volatile compounds were detected, but 22 were detected only in inoculated coffees. In spontaneous fermentation, 48 h of fermentation showed woody notes, while 72 h showed chestnuts. However, in the inoculated coffee, 72 h of fermentation showed high fruity dominance, and 96 h of fermentation was the only one with herbaceous notes. In addition, yeast inoculation increased the intensity of caramel notes in the first 48 h and increased the fruity flavor after 72 h of fermentation. Therefore, the type of fermentation (with or without inoculation) and the chosen fermentation time will depend on the sensorial profile the producer intends to obtain.

Enhancing biological control of postharvest green mold in lemons: Synergistic efficacy of native yeasts with diverse mechanisms of action.

Argentina is among the most important lemon fruit producers in the world. Penicillium digitatum is the primary lemon fungal phytopathogen, causing green mold during the postharvest. Several alternatives to the use of synthetic fungicides have been developed, being the use of biocontrol yeasts one of the most promising. Although many of the reports are based on the use of a single yeast species, it has been shown that the combination of agents with different mechanisms of action can increase control efficiency through synergistic effects. The combined use of native yeasts with different mechanisms of action had not been studied as a biological control strategy in lemons. In this work, the mechanisms of action of native yeasts (Clavispora lusitaniae AgL21, Clavispora lusitaniae AgL2 and Clavispora lusitaniae AcL2) with biocontrol activity against P. digitatum were evaluated. Isolate AgL21 was selected for its ability to form biofilm, colonize lemon wounds, and inhibit fungal spore germination. The compatibility of C. lusitaniae AgL21 with two killer yeasts of the species Kazachstania exigua (AcL4 and AcL8) was evaluated. In vivo assays were then carried out with the yeasts applied individually or mixed in equal cell concentrations. AgL21 alone was able to control green mold with 87.5% efficiency, while individual killer yeasts were significantly less efficient (43.3% and 38.3%, respectively). Inhibitory effects were increased when C. lusitaniae AgL21 and K. exigua strains were jointly applied. The most efficient treatment was the combination of AgL21 and AcL4, reaching 100% efficiency in wound protection. The combination of AgL21 with AcL8 was as well promising, with an efficiency of 97.5%. The combined application of native yeasts showed a synergistic effect considering that the multiple mechanisms of action involved could hinder the development of green mold in lemon more efficiently than using single yeasts. Therefore, this work demonstrates that the integration of native yeasts with diverse modes of action can provide new insights to formulate effective microbial consortia. This could lead to the development of tailor-made biofungicides, allowing control of postharvest fungal diseases in lemons while remaining competitive with traditionally used synthetic chemicals.

Freezing and thawing in Antarctica: characterization of antifreeze protein (AFP) producing microorganisms isolated from King George Island, Antarctica.

Antarctic temperature variations and long periods of freezing shaped the evolution of microorganisms with unique survival mechanisms. These resilient organisms exhibit several adaptations for life in extreme cold. In such ecosystems, microorganisms endure the absence of liquid water and exhibit resistance to freezing by producing water-binding molecules such as antifreeze proteins (AFP). AFPs modify the ice structure, lower the freezing point, and inhibit recrystallization. The objective of this study was to select and identify microorganisms isolated from different Antarctic ecosystems based on their resistance to temperatures below 0 °C. Furthermore, the study sought to characterize these microorganisms regarding their potential antifreeze adaptive mechanisms. Samples of soil, moss, permafrost, and marine sediment were collected on King George Island, located in the South Shetland archipelago, Antarctica. Bacteria and yeasts were isolated and subjected to freezing-resistance and ice recrystallization inhibition (IR) tests. A total of 215 microorganisms were isolated, out of which 118 were molecularly identified through molecular analysis using the 16S rRNA and ITS regions. Furthermore, our study identified 24 freezing-resistant isolates, including two yeasts and 22 bacteria. A total of 131 protein extracts were subjected to the IR test, revealing 14 isolates positive for AFP production. Finally, four isolates showed both freeze-resistance and IR activity (Arthrobacter sp. BGS04, Pseudomonas sp. BGS05, Cryobacterium sp. P64, and Acinetobacter sp. M1_25C). This study emphasizes the diversity of Antarctic microorganisms with the ability to tolerate freezing conditions. These microorganisms warrant further investigation to conduct a comprehensive analysis of their antifreeze capabilities, with the goal of exploring their potential for future biotechnological applications.

Selenized non-Saccharomyces yeasts and their potential use in fish feed.

Selenium (Se) is a vital trace element, essential for growth and other biological functions in fish. Its significance lies in its role as a fundamental component of selenoproteins, which are crucial for optimal functioning of the organism. The inclusion of Se in the diets of farmed animals, including fish, has proved invaluable in mitigating the challenges arising from elemental deficiencies experienced in captivity conditions due to limitations in the content of fishmeal. Supplementing diets with Se enhances physiological responses, particularly mitigates the effects of the continuous presence of environmental stress factors. Organic Se has been shown to have higher absorption rates and a greater impact on bioavailability and overall health than inorganic forms. A characteristic feature of yeasts is their rapid proliferation and growth, marked by efficient mineral assimilation. Most of the selenized yeasts currently available in the market, and used predominantly in animal production and aquaculture, are based on Saccharomyces cerevisiae, which contains selenomethionine (Se-Met). The object of this review is to highlight the importance of selenized yeasts. In addition, it presents metabolic and productive aspects of other yeast genera that are important potential sources of organic selenium. Some yeast strains discussed produce metabolites of interest such as lipids, pigments, and amino acids, which could have applications in aquaculture and further enrich their usefulness.

Biocompatibility of Brazilian native yeast-derived sophorolipids and Trichoderma harzianum as plant-growth promoting bioformulations.

The replacement of agrochemicals by biomolecules is imperative to mitigate soil contamination and inactivation of its core microbiota. Within this context, this study aimed at the interaction between a biological control agent such as Trichoderma harzianum CCT 2160 (BF-Th) and the biosurfactants (BSs) derived from the native Brazilian yeast Starmerella bombicola UFMG-CM-Y6419. Thereafter, their potential in germination of Oryza sativa L. seeds was tested. Both bioproducts were produced on site and characterized according to their chemical composition by HPLC-MS and GC-MS for BSs and SDS-PAGE gel for BF-Th. The BSs were confirmed to be sophorolipids (SLs) which is a well-studied compound with antimicrobial activity. The biocompatibility was examined by cultivating the fungus with SLs supplementation ranging from 0.1 to 2 g/L in solid and submerged fermentation. In solid state fermentation the supplementation of SLs enhanced spore production, conferring the synergy of both bioproducts. For the germination assays, bioformulations composed of SLs, BF-Th and combined (SLT) were applied in the germination of O. sativa L seeds achieving an improvement of up to 30% in morphological aspects such as root and shoot size as well as the presence of lateral roots. It was hypothesized that SLs were able to regulate phytohormones expression such as auxins and gibberellins during early stage of growth, pointing to their novel plant-growth stimulating properties. Thus, this study has pointed to the potential of hybrid bioformulations composed of biosurfactants and active endophytic fungal spores in order to augment the plant fitness and possibly the control of diseases.

Enhancing the quality and safety of Nocellara del Belice green table olives produced using the Castelvetrano method.

The Castelvetrano method is the most widely used among the various table olive processing styles in Sicily. After debittering, the product is stored at low temperatures to prevent the growth of undesirable microorganisms. In an effort to enhance the production process, yeast isolates underwent genotypic characterization and technological screening. The screening process identified two yeast strains Candida norvegica OC10 and Candida boidinii LC1, which can grow at low temperatures and tolerate high pH values (up to 10) and salinity [10% (w/v)]. During the monitoring period, the inoculated trials showed limited presence of spoilage/pathogenic microorganisms. Additionally, the yeasts limited oxidative phenomena and softening of the drupes. The organic compounds detected were higher in the inoculated trials than in the control, and cold storage induced aromatic decay, which was less pronounced in the trial inoculated with C. norvegica. Sensory analysis revealed that the inoculated trials scored higher in sweetness, hardness and crispness.

Study and characterization of a product based on a vegetable extract of quinoa fermented with water kefir grains.

This work aimed to study and characterize a product based on vegetable extract of quinoa (WVEQ) fermented with water kefir grains. The effect of sucrose concentration (SC), inulin concentration (IC), and xanthan gum (XG) concentration were evaluated using a central composite design (CCD) 23. They were subsequently characterized regarding cellular growth of the grains, beverage yield, pH, soluble solids, carbon dioxide (CO2) production, lactic acid, and ethanol production. Therefore, for the final stage, two formulations (F1 and F8) of the CCD were chosen to be characterized in terms of proximate composition, microbiological composition of the kefir culture, analysis of organic compounds, sensory analysis, and enzymatic and microbiological characterization before and after simulation of in vitro gastrointestinal digestion. In the two chosen products, one can see that fermentation optimized the bioavailability of proteins due to the high proteolytic activity of the microorganisms in kefir and the increase in lipid content. In identifying microorganisms, there was a prevalence of Saccharomyces sp. yeasts. In the sensory analysis, the F8 formulation showed better results than the F1 formulation. In vitro, gastrointestinal digestion showed reduced lactic acid bacteria and yeast and increased acetic acid bacteria in the liquid phase for both formulations. In the enzymatic profile, there was a reduction in all enzymes analyzed for both formulations, except for amylase in F1, which went from 14.05 U/mL to 39.41 U/mL. Therefore, it is concluded that using WVEQ as a substrate for the product appears to be a viable alternative with nutritional and technological advantages for serving a specific market niche.

Physiological evaluation of yeast strains under anaerobic conditions using glucose, fructose, or sucrose as the carbon source.

The aim of this study was to evaluate the physiology of 13 yeast strains by assessing their kinetic parameters under anaerobic conditions. They included Saccharomyces cerevisiae CAT-1 and 12 isolated yeasts from different regions in Brazil. The study aimed to enhance understanding of the metabolism of these strains for more effective applications. Measurements included quantification of sugars, ethanol, glycerol, and organic acids. Various kinetic parameters were analyzed, such as specific substrate utilization rate (qS), maximum specific growth rate (µmax), doubling time, biomass yield, product yield, maximum cell concentration, ethanol productivity (PEth), biomass productivity, and CO2 concentration. S. cerevisiae CAT-1 exhibited the highest values in glucose for µmax (0.35 h-1), qS (3.06 h-1), and PEth (0.69 gEth L-1 h-1). Candida parapsilosis Recol 37 did not fully consume the substrate. In fructose, S. cerevisiae CAT-1 stood out with higher values for µmax (0.25 h-1), qS (2.24 h-1), and PEth (0.60 gEth L-1 h-1). Meyerozyma guilliermondii Recol 09 and C. parapsilosis Recol 37 had prolonged fermentation times and residual substrate. In sucrose, only S. cerevisiae CAT-1, S. cerevisiae BB9, and Pichia kudriavzevii Recol 39 consumed all the substrate, displaying higher PEth (0.72, 0.51, and 0.44 gEth L-1 h-1, respectively) compared to other carbon sources.

Physiological characterization of polyextremotolerant yeasts from cold environments of Patagonia.

Yeasts from cold environments have a wide range of strategies to prevent the negative effects of extreme conditions, including the production of metabolites of biotechnological interest. We investigated the growth profile and production of metabolites in yeast species isolated from cold environments. Thirty-eight strains were tested for their ability to grow at different temperatures (5-30 °C) and solute concentrations (3-12.5% NaCl and 50% glucose). All strains tested were able to grow at 5 °C, and 77% were able to grow with 5% NaCl at 18 °C. We were able to group strains based on different physicochemical/lifestyle profiles such as polyextremotolerant, osmotolerant, psychrotolerant, or psychrophilic. Five strains were selected to study biomass and metabolite production (glycerol, trehalose, ergosterol, and mycosporines). These analyses revealed that the accumulation pattern of trehalose and ergosterol was related to each lifestyle profile. Also, our findings would suggest that mycosporines does not have a role as an osmolyte. Non-conventional fermentative yeasts such as Phaffia tasmanica and Saccharomyces eubayanus may be of interest for trehalose production. This work contributes to the knowledge of non-conventional yeasts with biotechnological application from cold environments, including their growth profile, metabolites, and biomass production under different conditions.

Dietary supplementation with live or autolyzed yeast: Effects on performance, nutrient digestibility, and ruminal fermentation in dairy cows.

This study was conducted to evaluate the effects of live or autolyzed yeast supplementation on dairy cow performance and ruminal fermentation. Two experiments were conducted to evaluate performance, feed sorting, total-tract apparent digestibility of nutrients, purine derivatives excretion, N utilization, ruminal fermentation, and the abundance of specific bacterial groups in the rumen. In experiment 1, 39 Holstein cows (171 ± 40 DIM and 32.6 ± 5.4 kg/d milk yield) were blocked according to parity, DIM, and milk yield and randomly assigned to the following treatments: control (CON); autolyzed yeast fed at 0.625 g/kg DM (AY; Levabon, DSM-Firmenich); or live yeast fed at 0.125 g/kg DM (LY; Vistacell, AB Vista). Cows were submitted to a 2-wk adaptation period followed by a 9-wk trial. In experiment 2, 8 ruminal cannulated Holstein cows (28.4 ± 4.0 kg/d milk yield and 216 ± 30 DIM), of which 4 were multiparous and 4 were primiparous, were blocked according to parity and enrolled into a 4 × 4 Latin square experiment with 21-d periods (the last 7 d for sampling). Cows within blocks were randomly assigned to treatment sequences: control (CON), LY (using the same product and dietary concentration as described in experiment 1), AY, or autolyzed yeast fed at 0.834 g/kg DM (AY2). In experiments 1 and 2, nutrient intake and total-tract apparent digestibility were not affected by treatments. Sorting for long feed particles (>19 mm) tended to be greater in cows fed yeast supplements than CON in experiment 1. Efficiency of N conversion into milk N was increased when feeding yeast supplements in experiment 1, and 3.5% FCM yield tended to be greater in cows fed yeast supplements than CON. Feed efficiency was increased when yeast supplements were fed to cows in relation to CON in experiment 1. In experiment 2, yield of FCM and fat were greater in cows fed yeast supplements compared with CON. Uric acid concentration and output in urine were increased when feeding yeast supplements when compared with CON. Neither ruminal pH nor total VFA were influenced by treatments. The current study did not reveal treatment differences in ruminal abundance of Anaerovibrio lipolytica, the genus Butyrivibrio, Fibrobacter succinogenes, Butyrivibrio proteoclasticus, or Streptococcus bovis. Yeast supplementation can increase feed efficiency without affecting nutrient intake and digestibility, ruminal VFA concentration, or ruminal abundance of specific bacterial groups. Supplementing live or autolyzed yeast, regardless of the dose, resulted in similar performance.

Biodiversity and brewing attitude of non-Saccharomyces strains isolated from Uruguayan vineyards and other ecosystems.

In recent years, interest in non-Saccharomyces yeasts for the innovation and development of different and alternative beer styles has been increasing, especially for the microbrewing industry. This work studied the biodiversity of non-Saccharomyces yeasts based on isolates from grapes of different Uruguayan vineyards, craft breweries and raw materials, with the aim of selecting autochthonous non-Saccharomyces yeasts with a brewing attitude. Brewing tests were performed on synthetic wort developed for this purpose, and the evolution of alcoholic fermentation was monitored by measuring glucose, maltose, maltotriose consumption, ethanol and glycerol production and final sensory analysis. A total of two hundred seventy-one yeast strains belonging to different genera were evaluated according to these parameters. After evaluating alcoholic fermentation performance, a native yeast strain belonging to the species Starmerella meliponinorum was selected due to its high maltotriose consumption and glycerol production, making it a very promising brewing yeast, especially for production of low carbohydrate beers.

Saprochaete/Magnusiomyces: identification, virulence factors, and antifungal susceptibility of a challenging rare yeast.

Saprochaete/Magnusiomyces is among rare yeasts which might emerge as causes of breakthrough infections and nosocomial outbreaks. Identification to the species level might be a challenge in clinical laboratories. Data on virulence factors are scarce and antifungal susceptibility testing methodology is not definite. The aim of this study was to confirm species identification of clinical Saprochaete/Magnusiomyces isolates, find out their virulence factors, and obtain antifungal minimum inhibitory concentrations with two reference methods. Of the 57 isolates included, 54 were Saprochaete capitata and four were Saprochaete clavata as identified by ID32C, MALDI-TOF MS, and sequencing. When tested using phenotypic methods, all isolates were negative for coagulase, hemolysis, acid proteinase, and phospholipase, 56.1% were positive for esterase, and 19.3% had intermediate surface hydrophobicity. All isolates formed biofilms, with 40.4% of the isolates producing more biomass than biofilm-positive reference strain Candida albicans MYA-274. Antifungal susceptibility testing needed an adjusted spectrophotometric inoculum than recommended in reference methods for Candida/Cryptococcus. In conclusion, Saprochaete/Magnusiomyces species could be identified using methods available in the clinical laboratories. Despite the disadvantages of the phenotypic methods, esterase positivity was observed for the first time. A high biomass production was observed in biofilms. The need for standardization of antifungal susceptibility testing was brought to attention.

Yeast diversity in open agave fermentations across Mexico.

Yeasts are a diverse group of fungal microorganisms that are widely used to produce fermented foods and beverages. In Mexico, open fermentations are used to obtain spirits from agave plants. Despite the prevalence of this traditional practice throughout the country, yeasts have only been isolated and studied from a limited number of distilleries. To systematically describe the diversity of yeast species from open agave fermentations, here we generate the YMX-1.0 culture collection by isolating 4524 strains from 68 sites with diverse climatic, geographical, and biological contexts. We used MALDI-TOF mass spectrometry for taxonomic classification and validated a subset of the strains by ITS and D1/D2 sequencing, which also revealed two potential novel species of Saccharomycetales. Overall, the composition of yeast communities was weakly associated with local variables and types of climate, yet a core set of six species was consistently isolated from most producing regions. To explore the intraspecific variation of the yeasts from agave fermentations, we sequenced the genomes of four isolates of the nonconventional yeast Kazachstania humilis. The genomes of these four strains were substantially distinct from a European isolate of the same species, suggesting that they may belong to different populations. Our work contributes to the understanding and conservation of an open fermentation system of great cultural and economic importance, providing a valuable resource to study the biology and genetic diversity of microorganisms living at the interface of natural and human-associated environments.

Optimization of xylanase production by Pichia kudriavzevii and Candida tropicalis isolated from the wood product workshop.

Enzymatic compounds can be found abundantly and provide numerous advantages in microbial organisms. Xylanases are used in various pharmaceutical, food, livestock, poultry, and paper industries. This study aimed to investigate xylanase-producing yeasts, xylose concentration curve and their enzymatic activity under various factors including carbon and nitrogen sources, temperature, and pH. Enzyme activity was evaluated under different conditions before, during, and after purification. The yeast strains were obtained from the wood product workshop and were subsequently cultivated on YPD (yeast extract peptone dextrose) medium. Additionally, the growth curve of the yeast and its molecular identification were conducted. The optimization and design process of xylan isolated from corn wood involved the use of Taguchi software to test different parameters like carbon and nitrogen sources, temperature, and pH, with the goal of determining the most optimal conditions for enzyme production. In addition, the Taguchi method was utilized to conduct a multifactorial optimization of xylanase enzyme activity. The isolated species were partially purified using ammonium sulfate precipitation and dialysis bag techniques. The results indicated that 3 species (8S, 18S, and 16W) after molecular identification based on 18S rRNA gene sequencing were identified as Candida tropicalis SBN-IAUF-1, Candida tropicalis SBN-IAUF-3, and Pichia kudriavzevii SBN-IAUF-2, respectively. The optimal parameters for wheat carbon source and peptone nitrogen source were found at 50 °C and pH 9.0 through single-factor optimization. By using the Taguchi approach, the best combination for highest activity was rice-derived carbon source and peptone nitrogen source at 50 °C and pH 6.0. The best conditions for xylanase enzyme production in single-factor optimization of wheat bran were 2135.6 U/mL, peptone 4475.25 U/mL, temperature 50 °C 1868 U/mL, and pH 9.0 2002.4 U/mL. Among the tested yeast, Candida tropicalis strain SBN-IAUF-1 to the access number MZ816946.1 in NCBI was found to be the best xylanase product. The highest ratio of enzyme production at the end of the delayed phase and the beginning of the logarithmic phase was concluded by comparing the growth ratio of 8S, 16W, and 18S yeasts with the level of enzymatic activity. This is the first report on the production of xylan polymer with a relative purity of 80% in Iran. The extracellular xylanases purified from the yeast species of C. tropicalis were introduced as a desirable biocatalyst due to their high enzymatic activity for the degradation of xylan polymers.