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Food Science & Nutrition Aug 2023Soybean paste was a traditional fermented product in northeast China, mainly fermented by molds, yeast, , and lactic acid bacteria. In this study, the safety and...
Soybean paste was a traditional fermented product in northeast China, mainly fermented by molds, yeast, , and lactic acid bacteria. In this study, the safety and fermentation ability of lactic acid bacteria and yeast strains isolated from traditional soybean paste in northeast China were evaluated, and the dynamic changes of biogenic amines, aflatoxin, total acids, amino acid nitrogen, and volatile compounds were investigated during the fermentation of the traditional soybean paste. Among the tested strains, DPUL-J8 could decompose putrescine by 100%, and no biogenic amine was produced by DPUY-J8. DPUL-J8 and DPUY-J8 with strong biogenic amine degrading capacities were inoculated into the soybean paste. After 30 days of fermentation, the content of biogenic amines and aflatoxin in the fermented soybean paste declined by more than 60% and 50%, respectively. At the same time, compared with the control group without inoculation, the contents of total acid (1.29 ± 0.05 g/100 g), amino acid nitrogen (0.82 ± 0.01 g/100 g), and volatile compounds in soybean paste fermented by DPUL-J8 and DPUY-J8 were significantly increased, which had a good flavor. These results indicated that the use of DPUL-J8 and DPUY-J8 as starter cultures for soybean paste might be a good strategy to improve the safety and flavor of traditional Chinese soybean paste.
PubMed: 37576040
DOI: 10.1002/fsn3.3372 -
Archives of Microbiology Aug 2023Recently, there has been growing interest in the characterization of native yeasts for their use in production of wines with regional characteristics. This study aimed...
Recently, there has been growing interest in the characterization of native yeasts for their use in production of wines with regional characteristics. This study aimed to investigate Saccharomyces and non-Saccharomyces yeasts present in the spontaneous fermentation of Tannat and Marselan grape musts collected from Concordia (Entre Ríos, Argentina) over 2019, 2020, and 2021 vintages. The evolution of these fermentative processes was carried out by measuring total soluble solids, total acidity, volatile acidity, pH, ethanol concentration, and total carbon content. Isolated Saccharomyces and non-Saccharomyces yeasts were identified based on colony morphology in WL medium, 5.8S-ITS-RFLP analysis, and 26S rDNA D1/D2 gene sequencing. Two hundred and ten yeast colonies were isolated and identified as Pichia kudriavzevii, Saccharomyces cerevisiae, Hanseniaspora uvarum, Metschnikowia pulcherrima, Candida albicans, Candida parapsilosis, Pichia occidentalis, Pichia bruneiensis, Hanseniaspora opuntiae, Issatchenkia terricola, and Hanseniaspora vineae. P. kudriavzevii isolated from all vintages was associated with the spontaneous fermentation of grape musts from the Concordia region.
Topics: Vitis; Fermentation; Yeasts; Wine; Saccharomyces cerevisiae; DNA, Ribosomal
PubMed: 37550458
DOI: 10.1007/s00203-023-03646-1 -
Mycoses Nov 2023Rapid and accurate yeasts species identification in clinical laboratories is important for appropriate and timely antifungal treatment. We evaluate the performance of...
Rapid and accurate yeasts species identification in clinical laboratories is important for appropriate and timely antifungal treatment. We evaluate the performance of the new medium CHROMagar™ Candida Plus for presumptive identification of yeasts species and MALDI-TOF identification. We identify 303 strains belonging to 60 clinically relevant yeasts species by using the new medium. Presumptive identification was correct at the Candida albicans complex, Candida tropicalis and Pichia kudriavzevii (Candida krusei) species. However, although this medium was able to identify all Candida auris and Candida glabrata strains, other species were misidentified as C. auris or C. glabrata. A total of 215 strains were identified by using MALDI-TOF and evaluated two incubation temperatures (30°C and 37°C) and two incubation times (24 h and 72 h). Most strains (94%; 202/215) were correctly identified at the species (n:190) or complex level (n:12) at both temperatures and incubation times. However, we observed that the time of incubation (24 h vs. 72 h) affects the score values when yeasts are incubated at 37°C, but does not affect score values when yeasts are incubated at 30°C. In conclusion, the new medium has a good performance in the presumptive identification of the C. albicans complex, C. tropicalis and P. kudriavzevii (C. krusei). In addition, this medium is useful for the screening of C. auris and C. glabrata isolates, but identification should be confirmed by other more specific techniques, like MALDI-TOF.
Topics: Humans; Candida; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Culture Media; Yeasts; Candida albicans; Candida glabrata; Candida tropicalis
PubMed: 37518770
DOI: 10.1111/myc.13633 -
Yeast (Chichester, England) Sep 2023During wet fermentation, mucilage layers in coffee cherries must be removed completely. To explain mucilage degradation, several controversial hypotheses have been...
During wet fermentation, mucilage layers in coffee cherries must be removed completely. To explain mucilage degradation, several controversial hypotheses have been proposed. The aim of this work was to improve our understanding of the kinetics of mucilage breakdown. Pulped coffee beans were wet fermented with seven different treatments for 36 h. Endogenous bacteria and yeasts are selectively suppressed, and pectinases or lactic acid are added. They also involve maintaining the beans at pH 7 throughout fermentation and using spontaneous fermentation without additives as a control. During spontaneous fermentation, yeast and lactic acid bacteria were detected and significantly increased to 5.5 log colony-forming units (CFU)/mL and 5.2 log CFU/mL, respectively. In the first 12 h of fermentation, there was a significant degree of endogenous pectinolytic activity, which resulted in partly destroyed beans in the absence of microorganisms. By adding pectinase and lactic acid to the fermentation mass, the breakdown process was accelerated in less than 8 h. When yeast was present throughout the fermentation, complete degradation was achieved. Bacteria played no critical role in the degradation. Klebsiella pneumoniae and Erwinia soli were found in a lower population and showed weaker pectinolytic activities compared to Hanseniaspora uvarum and Pichia kudriavzevii. During wet fermentation, mucilage degradation appears to be mediated by endogenous enzymes at the early stage, whereas microbial contributions, mainly yeasts, occur subsequently. H. uvarum and P. kudriavzevii may be promising candidates to be tested in future studies as coffee starter cultures to better control the mucilage degradation process.
Topics: Fermentation; Coffea; Yeasts; Bacteria; Polysaccharides; Lactic Acid
PubMed: 37464909
DOI: 10.1002/yea.3888 -
l-Lactic Acid Production via Sustainable Neutralizer-Free Route by Engineering Acid-Tolerant Yeast .Journal of Agricultural and Food... Jul 2023l-Lactic acid (l-LA) is a platform chemical obtained via microbial fermentation at a near-neutral pH value. Large amounts of neutralizers are required during this...
l-Lactic acid (l-LA) is a platform chemical obtained via microbial fermentation at a near-neutral pH value. Large amounts of neutralizers are required during this process, which increases the production costs in downstream processing as well as environmental burden. To address this challenge, an acid-tolerant yeast E1 was isolated and metabolically engineered to produce l-LA without neutralizers. The genome of strain E1 was sequenced and a CRISPR-Cas9 system was developed in this newly isolated strain. Subsequently, the gene encoding pyruvate decarboxylase () was knocked out to subdue ethanol formation. Furthermore, the l-lactate dehydrogenase gene from 2-6 and the codon-optimized gene from were introduced into E1 chromosome to redirect the ethanol fermentation pathway to l-LA production. Deletion of the () gene further increased the optical purity of l-LA. After optimizing fermentation conditions, the maximum titer of l-LA in the 5 L fermenter reached 74.57 g/L without any neutralizers, with an optical purity of 100% and a maximum yield of 0.93 g/g glucose. This is the first report of optically pure l-LA production without neutralizers and the engineered acid-tolerant yeast paves the way for the sustainable production of l-LA via a green route.
Topics: Animals; Cattle; Saccharomyces cerevisiae; Lactic Acid; Acids; Pichia; Fermentation; Ethanol
PubMed: 37439413
DOI: 10.1021/acs.jafc.3c03163 -
Mycopathologia Dec 2023We performed a retrospective survey of non-Candida albicans candidemia in patients with cancer, including those with solid tumors and those with hematological...
We performed a retrospective survey of non-Candida albicans candidemia in patients with cancer, including those with solid tumors and those with hematological malignancies as well as transplants patients both, solid-organ transplant recipients and hematopoietic stem cell transplant recipients. The study was performed at two healthcare centers in New York City and covered the years 2018-2022. A total of 292 patients (318 isolates) were included in the study. In order of frequency, C. glabrata (38%) was the most common species recovered, followed by C. parapsilosis (19.2%), C. tropicalis (12.6%), C. krusei (10.7%), C. lusitaniae (5.7%), and C. guilliermondii (4.4%). Micafungin was the most common antifungal treatment and 18.5% of patients were on antifungal prophylaxis. The 30-day crude mortality was 40%. 4.5% of patients had more than one non-albicans species detected. In conclusion, this study represents one of the largest surveys of non-albicans species in cancer and transplant patients and provides data on the current epidemiology of these Candida species in this patient population.
Topics: Humans; Antifungal Agents; Transplant Recipients; Retrospective Studies; Microbial Sensitivity Tests; Candida; Candidemia; Candida glabrata; Candida parapsilosis; Candida tropicalis; Neoplasms
PubMed: 37365379
DOI: 10.1007/s11046-023-00765-7 -
International Journal of Food... Aug 2023The increasing demand for more flavored and complex beers encourages the investigation of novel and non-conventional yeasts with the ability to provide a combination of...
The increasing demand for more flavored and complex beers encourages the investigation of novel and non-conventional yeasts with the ability to provide a combination of bioflavoring and low ethanol yields. The present study identified 22 yeasts isolated from different brewing sources, including the fermentation by-products known as yeast sludges, and characterized a selection of strains to find the more suitable for the aforementioned aims. HPLC and GC-FID analysis of its brewing products were performed. The most promising results were obtained with the non-conventional yeasts Pichia kudriavzevii MBELGA61 and Meyerozyma guilliermondii MUS122. The former, isolated from a Belgian wheat beer sludge, was capable of growing in wort (17.0°Bx., 20 °C) with very low ethanol yields (1.19 % v/v). Besides, upon mixed fermentations with Saccharomyces cerevisiae, was suitable to produce volatile compounds such as ethyl acetate, 2-phenyl ethanol and isoamyl alcohol, with characteristic fruity notes. M. guilliermondii MUS122, isolated from a golden ale beer sludge, partially attenuated the wort with low production of ethanol and biomass. In addition, provided some fruity and floral nuances to the aroma profile of mixed fermentations with brewer's yeast. The results suggest that these strains favor the development of more fruity-flowery aroma profiles in beers. Furthermore, they are suitable for use in mixed fermentations with Saccharomyces brewer's strains, although the ethanol level did not decrease significantly.
Topics: Fermentation; Beer; Sewage; Yeasts; Saccharomyces cerevisiae; Ethanol
PubMed: 37244227
DOI: 10.1016/j.ijfoodmicro.2023.110254 -
Applied Biochemistry and Biotechnology Aug 2023High-temperature ethanol fermentation (> 40 °C) can be applied as effective bioprocess technology to increase ethanol production. Thermotolerant yeast Pichia...
High-temperature ethanol fermentation (> 40 °C) can be applied as effective bioprocess technology to increase ethanol production. Thermotolerant yeast Pichia kudriavzevii 1P4 showed the ability to produce ethanol at optimum 37 °C. Thus, this study evaluated the ethanol productivity of isolate 1P4 at high-temperature ethanol fermentation (42 and 45 °C) and the identification of metabolite biomarkers using untargeted metabolomics with liquid chromatography-tandem mass spectrometry (LC-MS/MS). 1P4 showed tolerance to temperature stress up to 45 °C and thus relevant for high-temperature fermentation. As measured by gas chromatography (GC), bioethanol production of 1P4 at 30, 37, 42, and 45 °C was 5.8 g/l, 7.1 g/l, 5.1 g/l, and 2.8 g/l, respectively. The classification of biomarker compounds was based on orthogonal projection analysis to latent structure discriminant analysis (OPLS-DA), resulting in L-proline being a suspected biomarker compound for isolate 1P4 tolerance against high-temperature stress. Indeed, supplementation of L-proline on fermentation medium supported the growth of 1P4 at high temperatures (> 40 °C) than without L-proline. The bioethanol production with the addition of the L-proline resulted in the highest ethanol concentration (7.15 g/l) at 42 °C. Supplementation of L-proline as a stress-protective compound increased ethanol productivity at high-temperature fermentation of 42 and 45 °C by 36.35% and 83.33%, respectively, compared without the addition of L-proline. Preliminary interpretation of these results indicates that bioprocess engineering through supplementation of stress-protective compounds L-proline increases the fermentation efficiency of isolate 1P4 at higher temperatures (42 °C and 45 °C).
Topics: Fermentation; Temperature; Chromatography, Liquid; Tandem Mass Spectrometry; Gas Chromatography-Mass Spectrometry; Pichia; Yeasts; Ethanol
PubMed: 37103737
DOI: 10.1007/s12010-023-04554-2 -
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