Pichia Kudriavzevii Research Articles

Multi-Omics Analysis of the Co-Regulation of Wood Alcohol Accumulation in Baijiu Fermentation

Methanol, also known as wood alcohol, is a common hazardous by-product of alcoholic beverage fermentation and serves as a crucial indicator for assessing the safety of alcoholic beverages. However, the metabolic mechanisms of methanol production during the solid-state fermentation of Chinese Baijiu remain unclear. In this study, we sought to determine the primary stage of methanol production in Chinese Baijiu by measuring the methanol content at different stages of fermentation. High-throughput multi-omics sequencing techniques were employed to elucidate methanol metabolic pathways and associated microorganisms. In addition, a comprehensive analysis incorporating environmental factors and microbial interactions was conducted to explore their combined effects on methanol production. Methanol was predominantly produced during pit fermentation, with the most significant increase observed within the first seven days. Microorganisms such as Pichia kudriavzevii, Byssochlamys spectabilis, Penicillium, and Aspergillus played a regulatory role in methanol content during the first seven days through their involvement in butyrate and methane metabolic pathways and pectin degradation modules. During Baijiu production, various types of molds and yeasts participate in methanol production. Differences in their abundance within fermentation cycles may contribute to variations in methanol content between stages. Lactobacillus accumulated abundantly in the first seven days in each stage, suppressing methanol-metabolizing microorganisms. In addition, the increased acidity resulting from Lactobacillus metabolism may indirectly promote methanol generation.

Reduced lactic acid strengthens microbial community stability and function during Jiang-flavour Baijiu fermentation

Unravelling the relationships between microbial community stability and function under environmental stress is critical to understanding microbial ecology but remains understudied in fermentation ecosystems. In this study, the relationship between lactic acid and microbial community was revealed during Jiang-flavour Baijiu fermentation using high-throughput sequencing and nontargeted metabolomics. Lactic acid was reduced by mono- and co-inoculation of lactic acid-degrading strains, Pichia kudriavzevii and Zygosaccharomyces bailii. Furthermore, reduced lactic acid strengthened microbial community stability, mainly characterized by higher network modularity and more positive interactions of species. Lactic acid had a significantly negative relation with network modularity (P = 0.03, Pearson's r = − 0.97). Moreover, the increase in network stability contributed to stronger community function, as indicated by the increase in ethanol, total esters, and total alcohols. Finally, metabolic function analysis showed that amino acid metabolism, starch and sucrose metabolism, pyruvate metabolism, the TCA cycle, nucleotide sugar metabolism, pyrimidine metabolism, and purine metabolism were the main pathways resulting in changes in microbial community stability and function. This study indicated that microbial community stability and function can be enhanced by the regulation of environmental factors and provided a possible strategy for the steady-state regulation of the microbial community in Baijiu fermentation.

Isolation and characterisation of potential probiotic yeast strains from local fermented foods: Gastrointestinal tolerance and antimicrobial activity assessment

Probiotic microorganisms, offering health benefits when consumed in sufficient quantities, are gaining recognition for their potential role in promoting wellness. This study focuses on isolating and characterising potential probiotic yeast strains sourced from fermented food products. This research evaluates the gastrointestinal tolerance and antimicrobial activity of isolated yeast strains, with the potential application in probiotic supplements and functional foods. Yeast strains were isolated from fermented food sources and identified using morphological analysis, PCR, gene sequencing, and genetic identification. Gastrointestinal tolerance was assessed through simulated gastric fluid (SGF) exposure, and antimicrobial activity was tested against foodborne pathogens. Six yeast strains (Diutina mesorugosa, Pichia kudriavzevii, Candida mesorugosa, Candida sp) were identified. They exhibited varying resistance to low pH in SGF, suggesting survivability in the stomach. Some strains selectively inhibited specific Gram-negative pathogens like Pseudomonas aeruginosa and Salmonella sp. These findings suggest the isolated yeast strains may serve as probiotics, promoting digestive health and food safety. They are potentially used in probiotic supplements and functional foods, promising improved overall well-being.

Isolation, screening, and application of aroma-producing yeast for red dragon fruit wine

Nineteen yeast strains were screened from the soil, dead branches, and fruit peels of a dragon fruit orchard. The yeast strain Z03M was obtained through preliminary screening, rescreening, and sensory flavor evaluation. This strain has certain alcohol-producing characteristics and good aroma-producing performance. Based on morphological and molecular identification, it was identified as Pichia kudriavzevii. The differences in flavor in dragon fruit wine from natural fermentation, inoculation with strain Z03M, commercial yeast, and mixed fermentation were comprehensive analyzed and compared via high-performance liquid chromatography, gas chromatography-mass spectrometry and gas chromatography-ion mobility spectroscopy. During the fermentation process of dragon fruit wine, We found that strain Z03M preferentially utilizes glucose. Malic acid and lactic acid are the main organic acids found in dragon fruit wine. The relative contents of volatile flavor compounds such as alcohols, aldehydes, terpenes, and heterocyclics of dragon fruit wine fermented with strain Z03M were 71.11%, 4.34%, 0.32%, and 1.78%, respectively, which were significantly higher than those of the other fermented samples. Among them, the content of 3-methyl-1-butanol was high, providing a banana aroma to the dragon fruit wine. Additionally, the wine fermented by a mixture of strain Z03M and commercial yeast had a high content of ester compounds, indicating that mixed fermentation can improve the flavor quality of dragon fruit wine. The results of this study have the potential value for the production of dragon fruit wine and for the research and development of dragon fruit products.

Characterization of the effect of non-Saccharomyces cerevisiaes on the non-volatile constituents and volatile profiles of low-alcoholic pomegranate beverages

To create the low-alcoholic beverages with excellent nutritional properties and flavor qualities, pomegranate juice was fermented with 16 strains of non-Saccharomyces yeasts from 9 species without added sugar. The effects of different yeasts on the non-volatile constituents (vitamins, organic acids, polyphenols), volatile compounds and sensory characteristics of the fermented beverages were comprehensively evaluated. The study revealed that non-Saccharomyces fermentations resulted in a higher abundance of polyphenols compared to the pomegranate juice and S. cerevisiae WLS21 (Sc21). The monomer phenols in Meyerozyma guilliermondii 12 (Mg12) were approximately twice the total of CK and 1.3 times of Sc21. Moreover, they led to a higher concentration of volatile compounds than the pomegranate juice. A total of 94 volatile compounds were identified in the pomegranate fermented beverages. In contrast to S. cerevisiae, Wickerhamomyces anomalus 1-1 and 10 (Wa1-1, Wa10), Pichia kudriavzevii 8 (Pk8) and Mg12 resulted in more acetate esters, and Zygosaccharomyces rouxii IFO 1130 and 53 (Zr1130, Zr53) yield higher levels of ethyl esters. A total of 40 volatiles with a relative odour activity value (rOAV) of ≥ 0.1 were identified, of which 14 were selected for principal component analysis (PCA). The sensory analysis confirmed that Zr1130, Zr53, Wa1-1, Wa10 and Pk8 strains exhibited superior aroma generation compared to Sc21. Furthermore, the partial least-squares regression (PLSR) analysis revealed that cherry, red fruits, black currant, citrus fruits, raspberry, black berry, pineapple, floral, sour and alcoholic odours had a significantly positive impact on the overall acceptability of the fermented beverages.

Pulmonary surfactant impacts in vitro activity of selected antifungal drugs against Candida krusei and Candida albicans

PurposeThis study investigates how surfactants affect the in-vitro anti-infective efficacy of micafungin, caspofungin, anidulafungin, and amphotericin B in treating pulmonary mycoses.MethodsMIC values for antifungal agents were determined against Candida krusei (now Pichia kudriavzevii) ATCC 6258, Candida albicans ATCC 90028, and 18 clinical isolates using the broth microdilution method in RPMI medium, following EUCAST recommendations. MIC assays included testing with and without Curosurf® surfactant at 1 mg/mL for C. krusei ATCC 6258 and all C. krusei isolates. Subsequent Time-kill studies in Sabouraud broth involved testing both C. albicans ATCC 90028 and C. krusei ATCC 6258 strains at concentrations equal their respective MIC values, with and without surfactant, using all four antifungals. CFU/mL were assessed at multiple time points up to 24 h. TKCs with different surfactant concentrations for C. krusei ATCC 6258 and mini-TKCs at various concentrations relative to the MIC of C. krusei isolates and the reference strain were conducted with micafungin, anidulafungin, and caspofungin.ResultsMIC results showed that 1 µg/mL surfactant reduced killing of micafungin and anidulafungin against C. krusei, while caspofungin was unaffected. Amphotericin B's MIC decreased by half. TKCs demonstrated significant effects of surfactant on micafungin and anidulafungin against C. krusei, with complete abolition of anidulafungin's activity against C. albicans.ConclusionThis in-vitro study highlights the concentration-dependent inhibitory effect of surfactant on antifungal activity against C. krusei and, to some extent, C. albicans, necessitating further clinical validation for invasive lung mycoses treatment.

Insights of Pichia kudriavzevii SVMS2019 for cellulase production and fermentation into ethanol

The use of lignocellulosic biomass to produce value-added products, such as fuel ethanol, is a current priority for global biobased economy. The quest to explore novel microbes, such as yeasts, to attain sustainable products for an ever-growing population has become highly in demand. This study might be the first to explore the rumen yeast Pichia kudriavzevii SVMS2019 for cellulase production to efficiently utilize wheat straw as biomass, which can further be converted to bioethanol. The optimization process was carried out on pre-treated wheat straw by employing one factor at a time (OFAT) and response surface methodology (RSM). Wheat straw pre-treated using NaOH alkali pretreatment was characterized with FTIR, XRD, and SEM studies. The findings revealed that the P. kudriavzevii SVMS2019 obtained maximum cellulase activity of 44.064 IU/ml at 37.5 °C, pH 3.5, 120 h, and 1.5% of NaOH pre-treated wheat straw (substrate concentration) through RSM. It exhibited 1.25-fold increased production compared to OFAT. The stability of crude cellulase was observed at 45 °C and pH 6. Further, the hydrolyzed reducing sugars produced under optimal conditions opted for fermentation, with a maximum bioethanol content of 12.13 g/l obtained at 37.5 °C in a 24 h interval.

Divergent mitochondrial responses and metabolic signal pathways secure the azole resistance in Crabtree-positive and negative Candida species.

Azole drugs are the main therapeutic drugs for invasive fungal infections. However, azole-resistant strains appear repeatedly in the environment, posing a major threat to human health. Several reports have shown that mitochondria are associated with the virulence of pathogenic fungi. However, there are few studies on the mechanisms of mitochondria-mediated azoles resistance. Here, we first performed mitochondrial proteomic analysis on multiple Candida species (Candida albicans, Nakaseomyces glabrata, Pichia kudriavzevii, and Candida auris) and analyzed the differentially expressed mitochondrial proteins (DEMPs) between azole-sensitive and azole-resistant Candida species. Subsequently, we performed Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, gene ontology analysis, and protein-protein interaction network analysis of DEMPs. Our results showed that a total of 417, 165, and 25 DEMPs were identified in resistant C. albicans, N. glabrata, and C. auris, respectively. These DEMPs were enriched in ribosomal biogenesis at cytosol and mitochondria, tricarboxylic acid cycle, glycolysis, transporters, ergosterol, and cell wall mannan biosynthesis. The high activations of these cellular activities, found in C. albicans and C. auris (at low scale), were mostly opposite to those observed in two fermenter species-N. glabrata and P. kudriavzevii. Several transcription factors including Rtg3 were highly produced in resistant C. albicans that experienced a complex I activation of mitochondrial electron transport chain (ETC). The reduction of mitochondrial-related activities and complex IV/V of ETC in N. glabrata and P. kudriavzevii was companying with the reduced proteins of Tor1, Hog1, and Snf1/Snf4.IMPORTANCECandida spp. are common organisms that cause a variety of invasive diseases. However, Candida spp. are resistant to azoles, which hinders antifungal therapy. Exploring the drug-resistance mechanism of pathogenic Candida spp. will help improve the prevention and control strategy and discover new targets. Mitochondria, as an important organelle in eukaryotic cells, are closely related to a variety of cellular activities. However, the role of mitochondrial proteins in mediating azole resistance in Candida spp. has not been elucidated. Here, we analyzed the mitochondrial proteins and signaling pathways that mediate azole resistance in Candida spp. to provide ideas and references for solving the problem of azole resistance. Our work may offer new insights into the connection between mitochondria and azoles resistance in pathogenic fungi and highlight the potential clinical value of mitochondrial proteins in the treatment of invasive fungal infections.

Nitrogen Removal Mechanism and Microbial Community Changes of the MBR Bioaugmented with Two Novel Fungi Pichia kudriavzevii N7 and Candida tropicalis N9

Ammonia nitrogen wastewater causes dissolved oxygen concentrations to decrease and the content of harmful substances to increase. To characterize the application properties of two novel strains of highly efficient ammonium transforming fungi—Pichia kudriavzevii N7 and Candida tropicalis N9—this study used both as compound microbial agents to treat nitrogenous wastewater. Here, we investigated the bioaugmentation effect of compound fungi N7 and N9 in the MBR bioreactor and the effect of N7 and N9 on the fungal and bacterial microbial communities in the system. The results revealed that in the first week after inoculation of N7 and N9, the average removal rate of ammonium in the experimental and control groups were 89.43% and 82.86%, respectively, and the NO3−-N accumulation concentrations were 12.56 mg·L−1 and 17.73 mg·L−1, respectively. The average transformation rate of total nitrogen in the experimental and control groups were 46.32% and 30.6%, respectively. ITS sequencing results indicated that N9 could be a dominant fungus in the complex MBR system. The results of 16S rRNA sequencing showed that the dominant bacterial communities in the system were changed by the inoculation of compound fungi. Therefore, the compound fungi can be applied to strengthen the treatment of nitrogenous wastewater due to its compatibility.

PROBIOTIC MICROORGANISMS IN BREAD SOURDOUGHS

The review allows for characterization and evaluation of the typical microbiota and probiotic properties of individual species isolated from various bread sourdoughs. It has been observed that an interest in using sourdoughs for bread making and studying their microbiota has been steadily increasing in recent years. However, an analysis of contemporary publications has revealed insufficient information regarding microorganisms characteristic of sourdoughs based on spelt, buckwheat, corn, rice, teff, amaranth, quinoa, barley, oats, chia, sorghum, beans, and peas. The most studied sourdoughs are those based on wheat and rye flour. A list of the most prevalent lactic acid bacteria (LAB) and yeasts isolated from sourdoughs has been established. It comprises Companilactobacillus paralimentarius, Fructilactobacillus sanfranciscensis, Lactiplantibacillus plantarum, Latilactobacillus sakei, Leuconostoc citreum, Levilactobacillus brevis, Pediococcus pentosaceus, Weissella cibaria, Weissella confusa, as well as Kazachstania humilis, Kazachstania unispora, Pichia kudriavzevii, Pichia fermentans, Saccharomyces cerevisiae and Wickerhamomyces anomalus. All typical mentions of the probiotic properties of microorganisms isolated from bread sourdoughs have been described. When isolating probiotics from bread sourdoughs, special attention should be paid to such species of LAB as Lactiplantibacillus plantarum, Levilactobacillus brevis, Pediococcus pentosaceus, Enterococcus faecium, as well as the yeasts Saccharomyces cerevisiae and Kazachstania humilis, as they are quite commonly found in sourdoughs from various types of flour and have the most conspicuous probiotic properties. According to the review, it has been established that stress tolerance and antimicrobial activity are typical probiotic properties for microorganisms isolated from sourdoughs, although antioxidant properties require further research. Advances in technology and increased economic accessibility will lead to increased demand for new probiotic strains and microorganisms from bread sourdoughs and may help meet new levels of consumer needs.

Molecular typing and antifungal susceptibility profile of Candida krusei bloodstream isolates from Türkiye.

Candida krusei also known as Pichia kudriavzevii is a potentially multidrug-resistant yeast because it is intrinsically resistant to fluconazole and develops acquired resistance to echinocandins and polyenes. Here, we aim to provide a better understanding of the epidemiology and transmission modes of C. krusei infections by comparing invasive bloodstream (n=35) and non-invasive vaginal (n=20) C. krusei isolates. The genetic relatedness of the isolates was assessed using a newly described short tandem repeat (STR) analysis and their sensitivity to eight antifungal compounds was evaluated by antifungal susceptibility testing using the CLSI microbroth dilution method. All C. krusei isolates revealed unique STR genotypes, indicating the absence of clonal transmission in the study group. Furthermore, no drug-resistant or non-wild-type isolates were identified. Our findings demonstrated high resolution of STR genotyping for the detection and simultaneous genetic analysis of multiple C. krusei strains in clinical samples and excellent in vitro activity of common antifungal agents against invasive strains.

Differential consumption of malic acid and fructose in apple musts by Pichia kudriavzevii strains.

To assess the capability of Pichia kudriavzevii strains isolated from wine, cider, and natural environments in North Patagonia to produce ciders with reduced malic acid levels. Fermentation kinetics and malic acid consumption were assessed in synthetic media and in regional acidic apple musts. All P. kudriavzevii strains degraded malic acid and grew in synthetic media with malic acid as the sole carbon source. Among these strains, those isolated from cider exhibited higher fermentative capacity, mainly due to increased fructose utilization; however, a low capacity to consume sucrose present in the must was also observed for all strains. The NPCC1651 cider strain stood out for its malic acid consumption ability in high-malic acid Granny Smith apple must. Additionally, this strain produced high levels of glycerol as well as acceptable levels of acetic acid. On the other hand, Saccharomyces cerevisiae ÑIF8 reference strain isolated from Patagonian wine completely consumed reducing sugars and sucrose and showed an important capacity for malic acid consumption in apple must fermentations. Pichia kudriavzevii NPCC1651 strain isolated from cider evidenced interesting features for the consumption of malic acid and fructose in ciders.

Indole-3-Acetic Acid Producing Yeasts in the Phyllosphere of Legumes: Benefits for Chili Growth

Plant growth-promoting yeast (PGPY), which is associated with plants, has demonstrated the ability to enhance plant growth and crop yield and provide an effective alternative strategy for reducing the extensive use of chemical fertilizers. However, plant development and yield effects of the phyllosphere yeast have received comparatively little research. Therefore, 95 phylloplane yeast were isolated from the leaves of plants in Leguminosae, and their capability to produce indole-3-acetic acid (IAA) in yeast extract peptone dextrose (YPD) broth supplemented with L-tryptophan was evaluated in this research. Forty-two isolates were selected, due to their ability to produce IAA. Among these isolates, 7 showed high IAA production of more than 40 mg/g DW in YPD with tryptophan as the precursor. These strains were identified as Candida tropicalis, Pichia kudriavzevii and Tortispora caseinolytica based on morphological and D1/D2 domain of LSU rDNA sequence analysis. Other plant growth promotion traits, including the solubilization of phosphate, production of ammonia and siderophores and ACC deaminase activity, were also investigated. The results revealed that Candida tropicalis KPS2219 exhibited maximum IAA production of 54.10 mg/g DW, high ammonia production at 1.16 mg/mL and siderophore production. In a greenhouse experiment, the ability of C. tropicalis KPS2219 to enhance the growth of chili seedlings was investigated. The results revealed that seed priming followed by foliar spraying with C. tropicalis KPS2219 significantly increased the root length, shoot length, root dry weight and stem dry weight of the seedlings by 17.72, 29.15, 60 and 46.15 %, respectively, in comparison to those of the uninoculated control. These findings indicate the possibility of C. tropicalis KPS2219 as a bioinoculant to promote plant development and the effectiveness of foliar application. The efficacy of employing yeast consortiums to enhance growth will be investigated for further study. HIGHLIGHTS Phylloplane yeasts with remarkably high IAA production and multiple traits that promote the growth of plants were isolated from the new habitat, legumes. Spraying the yeast cells on the leaves of chili plants accelerated the growth of the plant. GRAPHICAL ABSTRACT

Non-Conventional Yeasts from Mozzarella Cheese Whey and Artisanal Sourdoughs: Leavening Capacity and Impact on Bread Sensory Profile

Non-conventional yeasts (NCYs) (i.e., non-Saccharomyces) are used as alternative starters to promote aroma complexity of fermented foods (e.g., bakery products). A total of 66 yeasts isolated from artisanal food matrices (bread and pizza sourdoughs and milk whey) from different geographical areas of the Campania region (Italy) were screened for physiological and technological characteristics such as leavening ability, resistance to NaCl and pH, exopolysaccharide and phytase activity production, and carbohydrate assimilation. Selected and isolated microorganisms were also used to study the leavening kinetics in experimental doughs as mixed inocula of two different strains. Volatile organic compounds (VOCs) of the inoculated doughs were analyzed with solid-phase microextraction/gas chromatography–mass spectrometry (SPME/GC-MS). Most of the strains belonged to non-Saccharomyces species (Pichia kudriavzevii, Kluyveromyces marxianus) and Saccharomyces (S. cerevisiae). Several strains produced exopolysaccharides (EPSs), that are important for dough rheological properties. Moreover, yeasts isolated from whey showed extracellular phytase activity. The mixed starter culture of the S. cerevisiae and NCY strains showed a synergic effect that enhanced the doughs’ aroma complexity. The use of non-conventional yeasts mixed with S. cerevisiae strains can be advantageous in the bakery industry because they improve the bread aroma profiles and nutritional properties by bioactive molecule production.

Effect of Yeast Inoculation on the Bacterial Community Structure in Reduced-Salt Harbin Dry Sausages: A Perspective of Fungi-Bacteria Interactions.

Yeast strains are promising starters to compensate for the flavor deficiencies of reduced-salt dry sausages, but their influence on the bacterial community's structure has not yet been clarified. In this study, the effect of separately inoculating Pichia kudriavzevii MDJ1 (Pk) and Debaryomyces hansenii HRB3 (Dh) on the bacterial community structure in reduced-salt dry sausage was investigated. The results demonstrated that the inoculation of two yeast strains significantly reduced the pH, and enhanced the total acid content, lactic acid bacteria (LAB) counts, and total bacterial counts of reduced-salt sausages after a 12-day fermentation (p < 0.05). Furthermore, high-throughput sequencing results elucidated that the inoculation of yeast strains significantly affected the bacterial composition of the dry sausages. Especially, the relative abundance of bacteria at the firmicute level in the Pk and Dh treatments exhibited a significant increase of 83.22% and 82.19%, respectively, compared to the noninoculated reduced-salt dry sausage treatment (Cr). The relative abundance of Latilactobacillus, especially L. sakei (0.46%, 2.80%, 65.88%, and 33.41% for the traditional dry sausage (Ct), Cr, Pk, and Dh treatments, respectively), increased significantly in the reduced-salt sausages inoculated with two yeast strains. Our work demonstrates the dynamic changes in the bacterial composition of reduced-salt sausages inoculated with different yeast strains, which could provide the foundation for the in-depth study of fungi-bacteria interactions in fermented foods.

β-glycosidase activity associated with the formation of aroma compounds in native non-Saccharomyces yeasts isolated from cocoa bean fermentation

Description of the subject. The use of non-Saccharomyces yeast for improving fine cocoa flavor perception has been poorly explored. Objectives. In this study, we investigated the contribution of the non-Saccharomyces yeasts producing β-glycosidase isolated from the spontaneous fermentation of cocoa to the quality and production of aromas during the alcoholic fermentation of a medium based on cocoa pulp. Method. The screening for β-glycosidase activity and molecular identification of non-Saccharomyces yeast isolates from Amazonian cocoa bean fermentations were performed on agar plates with esculin as a substrate and by 5.8S ITS rDNA sequence analysis, respectively. The yeasts producing β-glycosidases were used as a starter culture for alcoholic micro-fermentations of a medium based on cocoa pulp, incubated at 30 °C for 48 h. The quantification of organic acids, ethanol, and sugars was obtained by HPLC, and aroma compounds after cocoa pulp fermentation were identified by GC-FID and GC-MS. Results. Twenty-six non-Saccharomyces yeast isolates were selected by β-glycosidase activity, comprising species such as Pichia kudriavzevii (n = 15), Pichia sp. (n = 2), Pichia sporocuriosa (n = 1), Candida orthopsilosis (n = 3), Issatchenkia sp. (n = 1), I. orientalis (n = 1), and P. kudriavzevii/I. orientalis (n = 3). All yeast strains exhibited rapid growth in cocoa pulp medium, low ethanol production, high organic acid production, and higher glucose consume than fructose. These yeasts produced thirty different volatile compounds. The main groups included alcohols (3), esters (19), terpenes (4), phenols (2), organic acids (2), and aldehydes (3), with 67% of these having fruity and floral aromas. Pichia sp., P. kudriavzevii/I. orientalis and Issatchenckia sp. were the largest producers of volatile compounds. Notably, this study identified volatile compounds with fruity aromas previously unassociated with cocoa fermentations for the first time. Conclusions. These data demonstrate the potential of β-glycosidase-producing non-Saccharomyces yeasts to improve floral and fruity aromas, suggesting their promising use as a starter culture for cocoa fermentation.

Occurrence of pathogenic yeast species in artisanal cheeses from Boyacá, Colombia, including fluconazole resistant isolates.

Yeasts are widely known for their application in food production, but also because of their clinical significance. As human pathogens, several species of yeasts, mainly of the genus Candida and other closely related genera, are responsible for a great number of life-threatening infections. The occurrence of yeasts in cheeses, including pathogenic species, has been largely studied, yet the antifungal susceptibility of these microorganisms is rarely reported. Here, we identified the species and determined the antifungal susceptibility profile of 45 yeast Candida isolates recovered from artisanal cheeses from 20 cities in Boyacá, Colombia. Among the species, Pichia fermentans (28.9%) prevailed, followed by Pichia kudriavzevii (24.4%), Kluyveromyces marxianus (22.2%), Clavispora lusitaniae (11.1%), Candida inconspicua (6.7%) Candida parapsilosis (4.4%) and Meyerozyma guillermondii (2.2%). Notably, all seven species have been globally reported, to a greater or lesser extent, to cause fungemia and other invasive infections with high mortality rates. Remarkably, together with the intrinsically resistant P. kudriavzevii, most isolates of P. fermentans, C. inconspicua and C. parapsilosis were resistant to fluconazole, one of the most common drugs to treat candidiasis. Our findings highlight the importance of exploring the ecological niches of pathogenic yeasts, together with their antifungal susceptibility, considering that the emergence of resistance in non-commensal opportunistic pathogens poses a serious threat to public health.

Novel selenium-enriched Pichia kudriavzevii as a dietary supplement to alleviate dextran sulfate sodium-induced colitis in mice by modulating the gut microbiota and host metabolism.

Inflammatory bowel disease (IBD) poses persistent challenges due to its chronic and recurrent nature, exacerbated by the unsatisfactory outcomes of the traditional treatment approaches. In this study, we developed a dietary supplement, selenium-enriched Pichia kudriavzevii (SeY), to alleviate dextran sulfate sodium-induced colitis in mice. The newly developed functional food shows dual-functional activity, acting both as a probiotic and a reliable source of organic selenium. This study aimed to investigate the preventive effects of SeY against dextran sulfate sodium-induced colitis in mice and elucidate the underlying mechanisms. Results showed that SeY, especially at high doses (HSeY), significantly ameliorated colitis symptoms, reduced colonic damage, attenuated inflammatory responses, and mitigated oxidative stress. Furthermore, HSeY strengthened intestinal barrier function by increasing goblet cell numbers, upregulating MUC2 expression, and enhancing tight junction proteins (ZO-1, claudin-1, and occludin). Additionally, HSeY alleviated gut microbiota dysbiosis by promoting the colonization of beneficial bacteria such as norank-f-Muribaculaceae and Bacteroides, while suppressing harmful microorganisms such as norank-f-norank-o-Clostridia-UCG-014. The altered gut microbiota also affected gut metabolism, with differential metabolites primarily associated with amino acids, such as tryptophan metabolism, contributing to the mitigation of oxidative stress and inflammatory responses. Further studies involving antibiotic-mediated depletion of gut flora and fecal microbiota transfer trials corroborated that the preventive effect of HSeY against IBD relied on the gut microbiota. This study provides vital insights into colitis prevention and advances selenium-enriched fortified food-targeted nutritional interventions.

Evaluación de la actividad antimicrobiana de la bebida de kéfir contra escherichia coli, salmonella typhimurium y shigella flexneri

Objective: Evaluate the antimicrobial activity of the Kefir drink against Escherichia coli, Salmonella typhimurium and Shigella flexneri Method: The Kefir used in the investigation was acquired in Toluca, State of Mexico. We performed a reactivation of Kefir with pasteurized milk and analyzed 3 carbohydrates (honey, sugar and piloncillo) at different concentrations and times, 80, 100, 120% and 24, 48 and 72 hours respectively. Isolated cultivable microorganisms were characterized by phenotypic, biochemical and mass spectroscopy techniques. The initial and final pH were determined during the study time. The antimicrobial activity was carried out by extracting the metabolites present in the ferment with the Kirby-Bauer method, in addition the direct ferment was evaluated, to determine if there was inhibition with the Escherichia coli (ATCC 11229) strains, Salmonella typhimurium (ATCC 14028) and Shigella flexneri (ATCC 12022). Results: It was observed that in the three carbohydrates used at a concentration of 120% and at a time of 72 h, a lower pH was obtained (3.51 to 3.64) compared to their initial concentration (6.50 to 6.64). From the metabolites extracted in the different ferments, no inhibition halo was obtained with the strains analyzed. However, when using direct ferments, it was observed that in the carbohydrates used (sugar, honey, piloncillo) there was the presence of an inhibiting halo or the growth of colonies other than those evaluated. The isolated cultivable microorganisms were: Pichia kudriavzevii (yeast); Enterococcus sp (gram-positive coconut) and Lactobacillus sp (gram-positive bacillus). Conclusions : Kefir ferments made with different carbohydrates, came to present a degree of inhibition only as a consortium against Gram-negative microorganisms analyzed. Keywords: Kefir; fermentation microbiota; infection; antimicrobial activity

Screening and characterization of indigenous non-Saccharomyces cerevisiae with high enzyme activity for kiwifruit wine production

To explore the diversity and fermentation potential of non-Saccharomyces cerevisiae associated with kiwifruit, indigenous yeasts isolated from kiwifruit and natural fermentation were comprehensively analyzed. A total of 166 indigenous yeasts were isolated, of which 54 representative strains were used for subsequent enzyme activity characterization. Different colorimetric methods were used to verify the ability of these strains to secrete hydrolytic enzymes, and then six strains were selected for sequential fermentation by specific activity assay. The performance of indigenous yeasts in improving organic acids, polyphenols, volatile compounds and sensory characteristics of wines was evaluated holistically. Results indicated that most sequential fermentations exhibited significant improvements in vitamin C and polyphenols. Remarkably, the involvement of Zygosaccharomyces rouxii, Meyerozyma guilliermondii, and Pichia kudriavzevii increased the concentrations of ethyl esters, acetates and alcohols, enhancing floral and tropical fruit odors and ultimately achieving the highest overall sensory acceptability, thereby highlighting their potential in kiwifruit wine fermentation.