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Journal of Food Science and Technology Sep 2020Different types of yeasts and lactic acid bacteria dominate in spontaneously fermented products (food, beverages, and condiments) that are commonly consumed in Ethiopia....
Different types of yeasts and lactic acid bacteria dominate in spontaneously fermented products (food, beverages, and condiments) that are commonly consumed in Ethiopia. The aim of this study was to identify efficient fermentative yeasts from fermented foods, fermented beverages, honey and molasses using genotypic methods. Out of the 70 samples tested, 180 distinct wild yeast isolates were recovered. A total of 23 isolates were selected for genomic analysis based on their basis of biomass yield, fermentation capacity, and leavening performance. The nucleotide sequence analysis of the internal transcribed spacer ITS-5.8S rDNA region revealed that the indigenous yeast isolates had close relatedness to , , , and with greater than 97% nucleotide similarity. The study shows a high diversity of indigenous wild yeasts in fermented products and that potent strains had higher biomass yield, good gas production and remarkable leavening capacity that indicates their inherent potential for use in the baking industry.
PubMed: 32713962
DOI: 10.1007/s13197-020-04377-7 -
Journal of Dairy Science Mar 2021Biopreservation is defined as using microbes, their constituents, or both to control spoilage while satisfying consumer demand for clean-label products. The study...
Biopreservation is defined as using microbes, their constituents, or both to control spoilage while satisfying consumer demand for clean-label products. The study objective was to investigate the efficacy of bacterial cultures in biopreserving cottage cheese against postprocessing fungal contamination. Cottage cheese curd and dressing were sourced from a manufacturer in New York State. Dressing was inoculated with 3 different commercial protective cultures-PC1 (mix of Lacticaseibacillus spp. and Lactiplantibacillus spp.), PC2 (Lacticaseibacillus rhamnosus), and PC3 (Lactic. rhamnosus)-following the manufacturer recommended dosage and then mixed with curd. A control with no protective culture was included. Nine species of yeast (Candida zeylanoides, Clavispora lusitaniae, Debaryomyces hansenii, Debaryomyces prosopidis, Kluyveromyces marxianus, Meyerozyma guilliermondii, Pichia fermentans, Rhodotorula mucilaginosa, and Torulaspora delbrueckii) and 11 species of mold (Aspergillus cibarius, Aureobasidium pullulans, Penicillium chrysogenum, Penicillium citrinum, Penicillium commune, Penicillium decumbens, Penicillium roqueforti, Mucor genevensis, Mucor racemosus, Phoma dimorpha, and Trichoderma amazonicum) were included in the study. Fungi strains were previously isolated from dairy processing environments and were inoculated onto the cheese surface at a rate of 20 cfu/g. Cheese was stored at 6 ± 2°C. Yeast levels were enumerated at 0, 7, 14, and 21 d postinoculation. Mold growth was visually observed on a weekly basis through d 42 of storage and imaged. Overall, the protective cultures were limited in their ability to delay the outgrowth in cottage cheese, with only 8 of the 20 fungal strains showing an effect of the cultures compared with the control. The protective cultures were not very effective against yeast, with only PC1 able to delay the outgrowth of 3 strains: D. hansenii, Tor. delbrueckii, and Mey. guilliermondii. The efficacy of these protective cultures against molds in cottage cheese was more promising, with all protective cultures showing the ability to delay spoilage of at least 1 mold strain. Both PC1 and PC2 were able to delay Pen. chrysogenum and Pho. dimorpha outgrowth, and PC1 also delayed Pen. commune, Pen. decumbens, and Pen. roqueforti to different extents compared with the controls. This study demonstrates that commercial lactic acid bacteria cultures vary in their performance to delay mold and yeast outgrowth, and thus each protective culture should be evaluated against the specific strains of fungi of concern within each specific dairy facility.
Topics: Animals; Aspergillus; Cheese; Food Microbiology; Fungi; Hypocreales; Kluyveromyces; Mucor; New York; Penicillium; Pichia; Rhodotorula; Saccharomycetales
PubMed: 33455745
DOI: 10.3168/jds.2020-19136 -
Evaluation of the efficacy of commercial protective cultures against mold and yeast in queso fresco.Journal of Dairy Science Nov 2020In this study, we evaluated the efficacy of 3 commercial protective cultures designated PC1 (Lactobacillus spp.), PC2 (Lactobacillus rhamnosus), and PC3...
In this study, we evaluated the efficacy of 3 commercial protective cultures designated PC1 (Lactobacillus spp.), PC2 (Lactobacillus rhamnosus), and PC3 (Lactobacillus rhamnosus) as biopreservatives in queso fresco (QF) against 9 yeast strains (Candida zeylanoides, Clavispora lusitaniae, Debaryomyces hansenii, Debaryomyces prosopidis, Kluyveromyces marxianus, Meyerozyma guilliermondii, Pichia fermentans, Rhodotorula mucilaginosa, and Torulaspora delbrueckii) and 11 mold strains (Aspergillus cibarius, Aureobasidium pullulans, Penicillium chrysogenum, Penicillium citrinum, Penicillium commune, Penicillium decumbens, Penicillium roqueforti, Mucor genevensis, Mucor racemosus, Phoma dimorpha, and Trichoderma amazonicum). All fungal spoilage strains were previously isolated from dairy processing environments. A positive control (C) with no protective culture was included. Fungal spoilage organisms were inoculated on cheese surfaces at an inoculum level of 20 cfu/g, and cheeses were stored at 6 ± 2°C throughout the study. For yeast enumeration, cheeses were sampled on d 0, 7, 14, and 21 postinoculation. Significant inhibition was detected for each yeast strain by comparing yeast counts for each cheese treated with protective culture against the control cheese using one-way ANOVA with Bonferroni correction performed individually at d 7, 14, and 21 postinoculation. Mold growth was visually observed and imaged weekly through 70 d postinoculation. Whereas PC3 inhibited Cl. lusitaniae, Mey. guilliermondii, and Ph. dimorpha, PC2 inhibited the outgrowth of Cl. lusitaniae, D. hansenii, and Ph. dimorpha. Protective culture 1 had the broadest spectrum of efficacy across yeast and molds, delaying spoilage caused by 4 distinct yeast strains (Cl. lusitaniae, D. hansenii, D. prosopidis, and Mey. guilliermondii), and inhibiting visible growth of 2 mold strains (P. chrysogenum and Ph. dimorpha). Results demonstrated that commercial protective cultures vary in performance, as indicated by the breadth of mold and yeast inhibition at both the genus and species level. This study suggests that manufacturers looking into using protective cultures should investigate their efficacy against specific fungal strains of concern.
Topics: Animals; Cheese; Food Contamination; Food Microbiology; Fungi; Lactobacillus; Yeasts
PubMed: 32896415
DOI: 10.3168/jds.2020-18769 -
Frontiers in Bioengineering and... 2024Xylitol is a pentose-polyol widely applied in the food and pharmaceutical industry. It can be produced from lignocellulosic biomass, valorizing second-generation...
Xylitol is a pentose-polyol widely applied in the food and pharmaceutical industry. It can be produced from lignocellulosic biomass, valorizing second-generation feedstocks. Biotechnological production of xylitol requires scalable solutions suitable for industrial scale processes. Immobilized-cells systems offer numerous advantages. Although fungal pellet carriers have gained attention, their application in xylitol production remains unexplored. In this study, the yeast strain WC 1507 was employed for xylitol production. The optimal conditions were observed with free-cell cultures at pH above 3.5, low oxygenation, and medium containing (NH)SO and yeast extract as nitrogen sources (xylitol titer 79.4 g/L, Y 66.3%, and volumetric productivity 1.3 g/L/h). Yeast cells were immobilized using inactive pellet mycelial carrier (MC) and alginate beads (AB) and were tested in flasks over three consecutive production runs. Additionally, the effect of a 0.2% w/v alginate layer, coating the outer surface of the carriers (cMC and cAB, respectively), was examined. While Y values observed with both immobilized and free cells were similar, the immobilized cells exhibited lower final xylitol titer and volumetric productivity, likely due to mass transfer limitations. AB and cAB outperformed MC and cMC. The uncoated AB carriers were tested in a laboratory-scale airlift bioreactor, which demonstrated a progressive increase in xylitol production in a repeated batch process: in the third run, a xylitol titer of 63.0 g/L, Y of 61.5%, and volumetric productivity of 0.52 g/L/h were achieved. This study confirmed WC 1507 as a promising strain for xylitol production in both free- and entrapped-cells systems. Considering the performance of the wild strain, a metabolic engineering intervention aiming at further improving the efficiency of xylitol production could be justified. MC and AB proved to be viable supports for cell immobilization, but additional process development is necessary to identify the optimal bioreactor configuration and fermentation conditions.
PubMed: 38303913
DOI: 10.3389/fbioe.2024.1339093 -
Frontiers in Nutrition 2022Crataegi Fructus, a medicinal and edible herb in China, has been considered a popular dietary supplement globally. It is used for the treatment of dyspepsia and chronic...
Crataegi Fructus, a medicinal and edible herb in China, has been considered a popular dietary supplement globally. It is used for the treatment of dyspepsia and chronic heart failure according to the Chinese Pharmacopoeia (2020). However, fungal contamination in Crataegi Fructus affects its quality and safety, thus preventing its global promotion. In this study, we comprehensively studied the fungal community in processed products of Crataegi Fructus by high-throughput sequencing. A total of 21 Crataegi Fructus samples were collected from five provinces in China, and the samples were divided into five groups based on collection areas, as well as into three groups based on processing methods. We then targeted the internal transcribed spacer 2 sequence through the Illumina Miseq PE300 platform to investigate fungal composition and diversity. Results showed that all 21 samples were detected with fungal contamination, and Ascomycota was dominant at the phylum level. In the groups based on collection areas, Dothideomycetes, Pleosporaceae, and were dominant at the class, family, and genus levels, respectively. In the groups based on processing methods, Dothideomycetes, Aspergillaceae, and were the most abundant at the class, family, and genus levels, respectively. Differences in fungal communities between various groups were also observed. Furthermore, a total of 115 species were identified, among which seven were potential toxigenic, namely, , , , , , , and . In conclusion, this study reveals great fungal richness and diversity of Crataegi Fructus, providing references for the prevention and control of fungal contamination of Crataegi Fructus in practical production.
PubMed: 35634418
DOI: 10.3389/fnut.2022.883698 -
PloS One 2020Only quite recently, we have shown that yeast strains Clavispora lusitaniae 146 and Pichia fermentans 27 can act as efficient biocontrol agents for combating postharvest...
Only quite recently, we have shown that yeast strains Clavispora lusitaniae 146 and Pichia fermentans 27 can act as efficient biocontrol agents for combating postharvest fungal diseases in lemons. During postharvest and storage conditions, microorganisms are subject to different stress factors that could affect both their survival and their protective capacity. Understanding the tolerance of yeasts to environmental stress factors could support the future development and commercial application of biological control formulations based on such organisms. Thus, the impact of different stressors on the viability and protection efficiency of C. lusitaniae strain 146 and P. fermentans strain 27 was evaluated, and the yeasts were subjected to oxidative stress, thermal treatments, exposure to NaOCl, osmotic stress, and ultraviolet irradiation. Candida oleophila strain O served as the reference control. C. lusitaniae 146 was more resistant to H2O2 in plate assays; however, in liquid media there was no significant difference to the other strains. Strain 146 was less affected by NaOCl, being able to survive with 300 ppm. P. fermentans 27 was the strain most heavily affected by osmotic pressure, while strains 146 and strain O showed a similar adaptation. UV-B irradiation severely affected C. oleophila and P. fermentans, while C. lusitaniae was the most resistant. Strains 146 and 27 were similarly tolerant to thermal shocks, compared to the reference strain, which was less viable. In in vivo tests, exposure to 10 mM H2O2, 45°C or 200 ppm NaOCl prior to fruit inoculation, reduced the antagonistic activity against the pathogen Penicillium digitatum. However, in no case was the biocontrol efficiency reduced to less than 50%. As C. lusitaniae 146 demonstrated a great potential to combat P. digitatum under a wide range of conditions, the organism is a promising candidate as an effective and valuable alternative to toxic fungicides.
Topics: Citrus; Microbial Viability; Oxidative Stress; Pest Control, Biological; Saccharomycetales; Temperature
PubMed: 32946508
DOI: 10.1371/journal.pone.0239432 -
Journal of Fungi (Basel, Switzerland) Sep 2020Although species remain the leading cause of invasive fungal infections (IFI), the list of other isolated fungal pathogens is increasing. The aim of the study was to...
Although species remain the leading cause of invasive fungal infections (IFI), the list of other isolated fungal pathogens is increasing. The aim of the study was to report cases of IFI caused by rare yeasts in the largest tertiary Greek pediatric hospital. A retrospective study was performed from 6/2008-6/2020 regarding IFI caused by rare species. Identification of isolates was attained by conventional, molecular, and MALDI TOF MS methods, and susceptibility testing was performed according to the Clinical and Laboratory Standards (CLSI) methodology. During a 12-year period, 14 different rare fungal species in 33 neonates and children with IFI hospitalized in intensive care and oncology units were isolated from blood, central catheters, peritoneal, pleural, or pericardial fluid specimens. It is the first time for IFI caused by and in Greek neonates and children to be reported. For most of these rare fungal species isolated in the present study, no official antifungal breakpoints have been defined, and there are no guidelines for their treatment. Clinical laboratories should be aware of uncommon and emerging yeast pathogens and be able to detect them with molecular and proteomic methods.
PubMed: 32998455
DOI: 10.3390/jof6040194 -
Current Medical Mycology Jun 2015By using advanced detection/identification methods, the list of emerging uncommon opportunistic yeast infections is rapidly expanding worldwide. Our aim in the present...
BACKGROUND AND PURPOSE
By using advanced detection/identification methods, the list of emerging uncommon opportunistic yeast infections is rapidly expanding worldwide. Our aim in the present study was sequence-based species delineation of previously unidentified yeasts obtained from a clinically yeast collection.
MATERIALS AND METHODS
A total of twenty three out of the 855 (5.7%) yeast isolates which formerly remained unidentified by PCR-RFLP method, were subjected to sequence analysis of the entire internal transcribed spacers (ITS) regions of rDNA. The precise species recognition was performed by the comparison of the sequences with the reliable GenBank database.
RESULTS
Sequencing analysis of the ITS region of the strains revealed several uncommon yeasts that were not reported previously in Iran. The species include , , and .
CONCLUSION
We identified several rare clinical isolates selected from a big collection at the species level by ITS-sequencing. As the list of yeast species as opportunistic human fungal infections is increasing dramatically, and many isolates remain unidentified using conventional methods, more sensitive and specific advanced approaches help us to clarify the aspects of microbial epidemiology of the yeast infections.
PubMed: 28680981
DOI: 10.18869/acadpub.cmm.1.2.1 -
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 -
Tropical Biomedicine Aug 2011The biodiversity and the killer activity of yeasts isolated from various types of fermented food in Malaysia were investigated in this study. Of 252 yeasts isolated from...
The biodiversity and the killer activity of yeasts isolated from various types of fermented food in Malaysia were investigated in this study. Of 252 yeasts isolated from 48 fermented food samples in this study, 19 yeast species were identified based on sequence analysis of the ITS1-5.8S-ITS2 partial fragments of the yeasts. A total of 29 (11.5%) of the yeast isolates demonstrated killer activity to at least one Candida species tested in this study; including 22 isolates of Trichosporon asahii, 4 isolates of Pichia anomala, and one isolate each of Pichia norvegensis, Pichia fermentans and Issatchenkia orientalis, respectively. The presence of killer yeasts reflects antagonism that occurs during microbial interaction in the fermented food, whereby certain yeasts produce killer toxins and possibly other toxic substances in competition for limited nutrients and space. The anti-Candida activity demonstrated by killer yeasts in this study should be further explored for development of alternative therapy against candidiasis.
Topics: Antibiosis; DNA, Fungal; DNA, Ribosomal; DNA, Ribosomal Spacer; Food Microbiology; Genes, rRNA; Malaysia; RNA, Fungal; RNA, Ribosomal, 5.8S; Sequence Analysis, DNA; Yeasts
PubMed: 22041766
DOI: No ID Found