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Foods (Basel, Switzerland) Jul 2023Yeast and lactic acid bacteria (LAB) are known to play an important role in the fermentation process of coffee post-harvest. This study aimed to isolate and screen yeast...
Yeast and lactic acid bacteria (LAB) are known to play an important role in the fermentation process of coffee post-harvest. This study aimed to isolate and screen yeast and LAB to be applied in lab-scale refermentation of commercial green coffee beans and coffee pulp with the aim of modifying the composition of organic acids (OAs) in coffee beans. Yeast and LAB strains were isolated from green coffee beans and dry coffee pulp and identified, and their effect on OA concentration in the coffee beans was quantified. In addition, the effects of different fermentation conditions (additional carbon source, different inoculum dose, and different types of coffee pulp) were evaluated based on OA quantification. Nine yeast isolates of and were identified, and 11 LAB isolates of the species were identified. Of the 7 OAs quantified, quinic acid was the most abundant. The inoculation of isolated yeasts and LAB led to higher concentrations of OAs, showing the potential to realize modification of the OA composition of green coffee beans by re-fermentation with coffee-originated isolates.
PubMed: 37444360
DOI: 10.3390/foods12132622 -
Frontiers in Microbiology 2023It is shown that bacteria use yeast as a niche for survival in stressful conditions, therefore yeasts may act as temporary or permanent bacterial reservoirs....
It is shown that bacteria use yeast as a niche for survival in stressful conditions, therefore yeasts may act as temporary or permanent bacterial reservoirs. Endobacteria colonise the fungal vacuole of various osmotolerant yeasts which survive and multiply in sugar-rich sources such as plant nectars. Nectar-associated yeasts are present even in the digestive system of insects and often establish mutualistic symbioses with both hosts. Research on insect microbial symbioses is increasing but bacterial-fungal interactions are yet unexplored. Here, we have focused on the endobacteria of (formerly and ), an osmotolerant yeast associated with sugar sources and the insect gut Symbiotic strains of influence larval development and contribute digestive processes in adults, in addition to exerting wide antimicrobial properties for host defence in diverse insects including mosquitoes. Antiplasmodial effects of have been shown in the gut of the female malaria vector mosquito . This discovery highlights the potential of utilizing yeast as a promising tool for symbiotic control of mosquito-borne diseases. In the present study, we have carried out a large Next Generation Sequencing (NGS) metagenomics analysis including strains associated with vector mosquitoes , and , which has highlighted wide and heterogeneous EB communities in yeast. Furthermore, we have disclosed a Matryoshka-like association in the gut of that comprises different EB in the strain of F17.12. Our investigations started with the localization of fast-moving bacteria-like bodies within the yeast vacuole of F17.12. Additional microscopy analyses have validated the presence of alive intravacuolar bacteria and 16S rDNA libraries from F17.12 have identified a few bacterial targets. Some of these EB have been isolated and tested for lytic properties and capability to re-infect the yeast cell. Moreover, a selective competence to enter yeast cell has been shown comparing different bacteria. We suggested possible tripartite interactions among EB, and the host, opening new knowledge on the vector biology.
PubMed: 37396392
DOI: 10.3389/fmicb.2023.1157299 -
Microorganisms Jun 2023previously known as occasionally causes candidemia in humans, primarily infecting neonates, and infants. The mortality rate of these invasive infections is high, and...
previously known as occasionally causes candidemia in humans, primarily infecting neonates, and infants. The mortality rate of these invasive infections is high, and isolates with a reduced susceptibility to fluconazole have been reported. outbreaks are regularly reported in healthcare facilities, especially in neonatal intensive care units (NICUs). In order to rapidly genotype isolates with a high-resolution, we developed and applied a short tandem repeat (STR) typing scheme for . Six STR markers were selected and amplified in two multiplex PCRs, M3 and M6, respectively. In total, 90 isolates were typed, leading to the identification of 38 different genotypes. Four large clusters were found, unveiling simultaneous outbreak events spread across multiple units within the same hospital. STR typing results of 11 isolates were compared to whole-genome sequencing (WGS) single nucleotide polymorphism (SNP) calling, and the identified genotypic relationships were highly concordant. We performed antifungal susceptibility testing of these isolates, and a reduced susceptibility to fluconazole was found for two (2.3%) isolates. genes of these two isolates were examined using WGS data, which revealed a novel I469L substitution in one isolate. By constructing a homology model for , the substitution was found in close proximity to the fluconazole binding site. In summary, we showed multiple outbreak events by applying a novel STR genotyping scheme.
PubMed: 37375027
DOI: 10.3390/microorganisms11061525 -
Foods (Basel, Switzerland) Jun 2023Microbial and biochemical changes in the brine during the spontaneous fermentation of Gordal, Hojiblanca and Manzanilla olive cultivars processed according to the...
Microbial and biochemical changes in the brine during the spontaneous fermentation of Gordal, Hojiblanca and Manzanilla olive cultivars processed according to the natural style were monitored. The microbial composition was assessed through a metagenomic study. Sugars, ethanol, glycerol, organic acids and phenolic compounds were quantified by standard methods. In addition, the volatile profiles, contents of phenolic compounds in the olives and quality parameters of the final products were compared. Fermentation in Gordal brines was conducted by lactic acid bacteria (mainly and ) and yeasts (mainly , and ). In Hojiblanca and Manzanilla brines, halophilic Gram-negative bacteria (e.g., , and ) along with yeasts (mainly, ) were responsible for the fermentation. Higher acidity and lower pH values were reached in Gordal brines compared to Hojiblanca and Manzanilla. After 30 days of fermentation, no sugars were detected in Gordal brine, but residual amounts were found in the brines from Hojiblanca (<0.2 g/L glucose) and Manzanilla (2.9 g/L glucose and 0.2 g/L fructose). Lactic acid was the main acid product in Gordal fermentation, whereas citric acid was the predominant organic acid in the Hojiblanca and Manzanilla brines. Manzanilla brine samples showed a greater concentration of phenolic compounds than Hojiblanca and Gordal brines. After a 6-month fermentation, Gordal olives were superior compared to the Hojiblanca and Manzanilla varieties regarding product safety (lower final pH and absence of ), content of volatile compounds (richer aroma), content of bitter phenolics (lower content of oleuropein, which resulted in less perceived bitterness) and color parameters (more yellow and lighter color, indicating a higher visual appraisal). The results of the present study will contribute to a better understanding of each fermentation process and could help to promote natural-style elaborations using the above-mentioned olive cultivars.
PubMed: 37372597
DOI: 10.3390/foods12122386 -
Foods (Basel, Switzerland) Jun 2023Rice, supplemented with , was subjected to cofermentation using FBKL2.8022 () and FBKL2.8023 (). The alcohol content was determined with a biosensor, total sugars with...
Rice, supplemented with , was subjected to cofermentation using FBKL2.8022 () and FBKL2.8023 (). The alcohol content was determined with a biosensor, total sugars with the phenol-sulfuric acid method, reducing sugars with the DNS method, total acids and total phenols with the colorimetric method, and metabolites were analyzed using LC-MS/MS combined with multivariate statistics, while metabolic pathways were constructed using metaboAnalyst 5.0. It was found that the quality of rice wine was higher with the addition of . A total of 127 major active substances, mainly phenols, flavonoids, terpenoids, alkaloids, and phenylpropanoids, were identified. Among them, 26 substances might have been mainly metabolized by the mixed-yeasts fermentation itself, and 10 substances might have originated either from itself or from microbial metabolism on the newly supplemented substrate. In addition, significant differences in metabolite could be attributed to amino acid metabolic pathways, such as phenylalanine metabolism and alanine, aspartate, and glutamate metabolism. The characteristic microbial metabolism of produces metabolites, which are α-dihydroartemisinin, alantolactone, neohesperidin dihydrochalcone, and occidentoside. This study showed that mixed-yeasts cofermentation and fermentation with both could increase the content of active substances in rice wine and significantly improve the quality of rice wine. The results of this study provide a reference for the mixed fermentation of brewer's yeast and non-yeast yeasts in rice wine brewing.
PubMed: 37372580
DOI: 10.3390/foods12122370 -
Frontiers in Microbiology 2023Ethanol tolerance is crucial for the oenological yeasts. Tratt, a Rosaceae plant native to China, is rich in nutritional and medicinal ingredients. In this study,...
Ethanol tolerance is crucial for the oenological yeasts. Tratt, a Rosaceae plant native to China, is rich in nutritional and medicinal ingredients. In this study, ethanol-tolerant non- yeasts were screened, and their oenological properties were further evaluated. Three ethanol-tolerant yeast strains (designated as C6, F112, and F15), which could tolerate 12% (v/v) ethanol treatment, were isolated from , and identified as , , and , respectively. The winemaking condition tolerances of these ethanol-tolerant yeast strains were similar to those of X16. However, their growth, sugar metabolic performance and sulphureted hydrogen activities, were different. The β-glucosidase production ability of strain F15 was lower than that of X16, and strains of C6 and F112 were similar to X16. Electronic sensory properties of the wines fermented using ethanol-tolerant yeasts together with showed no significant differences. However, the mixed inoculation of the ethanol-tolerant yeast strains with could regulate the volatile aroma characteristics of the fermented wine, enriching and enhancing the aroma flavor. Therefore, the selected ethanol-tolerant yeasts have the potential for application in the production of unique wine.
PubMed: 37323890
DOI: 10.3389/fmicb.2023.1202440 -
Microorganisms Apr 2023Drinking wine is a processed beverage that offers high nutritional and health benefits. It is produced from grape must, which undergoes fermentation by yeasts (and... (Review)
Review
Drinking wine is a processed beverage that offers high nutritional and health benefits. It is produced from grape must, which undergoes fermentation by yeasts (and sometimes lactic acid bacteria) to create a product that is highly appreciated by consumers worldwide. However, if only one type of yeast, specifically , was used in the fermentation process, the resulting wine would lack aroma and flavor and may be rejected by consumers. To produce wine with a desirable taste and aroma, non- yeasts are necessary. These yeasts contribute volatile aromatic compounds that significantly impact the wine's final taste. They promote the release of primary aromatic compounds through a sequential hydrolysis mechanism involving several glycosidases unique to these yeasts. This review will discuss the unique characteristics of these yeasts (, , , , , , , , and others) and their impact on wine fermentations and co-fermentations. Their existence and the metabolites they produce enhance the complexity of wine flavor, resulting in a more enjoyable drinking experience.
PubMed: 37317152
DOI: 10.3390/microorganisms11051178 -
International Journal of Food... Aug 2023In the present study, the physicochemical (pH, water activity, moisture content, salt concentration) classical plate counts (total viable counts, yeasts, lactic acid...
In the present study, the physicochemical (pH, water activity, moisture content, salt concentration) classical plate counts (total viable counts, yeasts, lactic acid bacteria, Staphylococcus aureus, Pseudomonas spp., Enterobacteriaceae) and amplicon sequencing of naturally black dry-salted olives obtained from different retail outlets of the Greek market were investigated. According to the results, the values of the physicochemical characteristics presented great variability among the samples. Specifically, pH and water activity (a) values ranged between 4.0 and 5.0, as well as between 0.58 and 0.91, respectively. Moisture content varied between 17.3 and 56.7 % (g ΗΟ/100 g of olive pulp), whereas salt concentration ranged from 5.26 to 9.15 % (g NaCl/100 g of olive pulp). No lactic acid bacteria, S. aureus, Pseudomonas spp. and Enterobacteriaceae were detected. The mycobiota consisted of yeasts that were further characterized and identified by culture-dependent (rep-PCR, ITS-PCR, and RFLP) and amplicon target sequencing (ATS). Pichia membranifaciens, Candida sorbosivorans, Citeromyces nyonsensis, Candida etchelsii, Wickerhamomyces subpelliculosus, Candida apicola, Wickerhamomyces anomalus, Torulaspora delbrueckii and Candida versatilis were the dominant species according to ITS sequencing (culture-dependent), while ATS revealed the dominance of C. etchelsii, Pichia triangularis, P. membranifaciens, and C. versatilis among samples. The results of this study demonstrated considerable variability in quality attributes among the different commercial samples of dry-salted olives, reflecting a lack of standardization in the processing of this commercial style. However, the majority of the samples were characterized by satisfactory microbiological and hygienic quality and complied with the requirements of the trade standard for table olives of the International Olive Council (IOC) for this processing style in terms of salt concentration. In addition, the diversity of yeast species was elucidated for the first time in commercially available products, increasing our knowledge on the microbial ecology of this traditional food. Further investigation into the technological and multifunctional traits of the dominant yeast species may result in better control during dry-salting and enhance the quality and shelf-life of the final product.
Topics: Sodium Chloride; Olea; Staphylococcus aureus; Greece; Food Microbiology; Yeasts; Enterobacteriaceae; Fermentation
PubMed: 37120943
DOI: 10.1016/j.ijfoodmicro.2023.110226 -
Food Microbiology Aug 2023To turn table olives into appropriate carriers of beneficial bacteria and yeasts to consumers, it is essential to have reliable methods for analysing microorganisms in...
To turn table olives into appropriate carriers of beneficial bacteria and yeasts to consumers, it is essential to have reliable methods for analysing microorganisms in biofilms. This work validates the application of a non-destructive procedure to study the lactic acid bacteria and yeasts distribution in fruits during Spanish-style green table olive fermentations. Laboratory-scale fermentations were inoculated simultaneously with three Lactiplantibacillus pentosus strains (LPG1, 119, and 13B4) and two yeasts (Wickerhamomyces anomalus Y12 and Saccharomyces cerevisiae Y30), all of them natives of table olive fermentations. Data showed that L. pentosus LPG1 and yeasts W. anomalus Y12 were quite prone to colonise olive biofilms, but only the Lactiplantibacillus strain also can penetrate the epidermis of the fruit and colonise the flesh. Applying a non-destructive treatment consisting in shelling the fruits with glass beads led to obtaining similar lactic acid bacteria and yeast recovery than the classical stomacher destructive method. However, the glass bead procedure improved the quality of the metagenomics analysis (especially when using 16 S rRNA gene-based sequencing). Results show the great utility of procedures that do not destroy the fruit for studying fermented vegetable biofilms.
Topics: Lactobacillales; Olea; Yeasts; Lactobacillaceae; Biofilms; Saccharomyces cerevisiae; Fermentation; Food Microbiology
PubMed: 37098438
DOI: 10.1016/j.fm.2023.104250 -
Food Microbiology Aug 2023Contamination of white-brined cheeses (WBCs) with yeasts is of major concern in the dairy industry. This study aimed to identify yeast contaminants and characterize...
Contamination of white-brined cheeses (WBCs) with yeasts is of major concern in the dairy industry. This study aimed to identify yeast contaminants and characterize their succession in white-brined cheese during a shelf-life of 52 weeks. White-brined cheeses added herbs (WBC1) or sundried tomatoes (WBC2) were produced at a Danish dairy and incubated at 5 °C and 10 °C. An increase in yeast counts was observed for both products within the first 12-14 weeks of incubation and stabilized afterwards varying in a range of 4.19-7.08 log CFU/g. Interestingly, higher incubation temperature, especially in WBC2, led to lower yeast counts, concurrently with higher diversity of yeast species. Observed decrease in yeast counts was, most likely, due to negative interactions between yeast species leading to growth inhibition. In total, 469 yeast isolates from WBC1 and WBC2 were genotypically classified using the (GTG)-rep-PCR technique. Out of them, 132 representative isolates were further identified by sequencing the D1/D2 domain of the 26 S rRNA gene. Predominant yeast species in WBCs were Candida zeylanoides and Debaryomyces hansenii, while Candida parapsilosis, Kazachstania bulderi, Kluyveromyces lactis, Pichia fermentans, Pichia kudriavzevii, Rhodotorula mucilaginosa, Torulaspora delbrueckii, and Wickerhamomyces anomalus were found in lower frequency. Heterogeneity of yeast species in WBC2 was generally larger compared to WBC1. This study indicated that, along with contamination levels, taxonomic heterogeneity of yeasts is an important factor influencing yeast cell counts, as well as product quality during storage.
Topics: Cheese; Yeasts; Polymerase Chain Reaction
PubMed: 37098422
DOI: 10.1016/j.fm.2023.104266