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At least 19 recordsLinked to original sources
PubMed2026

Metagenomic Insights into Microbial Assembly and Key Metabolic Genes Driving Flavor Formation in Spontaneously Fermented Zhejiang Rosy Vinegar.

The spontaneous fermentation of Zhejiang rosy vinegar (ZRV) is driven by environmental microbiota, but the processes underlying its flavor formation remain poorly understood. Using metagenomic sequencing, we investigated microbial community assembly, environmental drivers, and metabolic networks during industrial-scale ZRV fermentation. Acetic acid dominated the final organic acids. Community assembly shifted toward deterministic selection with rising acidity, with a slight rebound of stochastic processes in the late stage (R2 values of 0.442 and 0.346 for bacteria and fungi, respectively). Mantel tests confirmed that environmental factors significantly regulated microbial assembly. Co-occurrence networks grew more complex, with positive interactions accounting for 85.24% (bacteria) and 90.10% (fungi) in the late stage. Key genes (ldh, gapA, pgk) from Acetobacter pasteurianus and Lactobacillus acetotolerans dominated late-stage fermentation, while genes (adhP, SDH) from Aspergillus oryzae and Saccharomyces cerevisiae supported early- and mid-stage fermentation. These findings elucidate microbiota-driven metabolic pathways in ZRV, supporting the fermentation window optimization and industrial vinegar quality standardization.

Acetic Acid↗
PubMed1992

Characterization of killer-resistant strains of Saccharomyces cerevisiae isolated from spontaneous fermentations.

A study of 26 killer-resistant wine strains of Saccharomyces cerevisiae, isolated during spontaneous fermentations in three vineyards in NW Spain, was carried out employing several methods that included a spheroplast-killing assay and analysis of chromosomal DNA patterns by pulse-field agarose electrophoresis. The results showed that 92% of the strains were derivatives of K2 killer toxin producing wine strains isolated from the same fermentations, and that they could be grouped into four different karyotypes. The remaining strains were killer-resistant at cell-wall level and were not related to the others, as was demonstrated by the absence of L and M ds-RNAs and by their different karyotypes.

DNA, Fungal↗
PubMed1989

[Yeasts associated with spontaneous fermentation processes in wines from Ribeiro. Analysis of homo/heterothallism and the killer system of S. cerevisiae strains].

A taxonomic analysis has been carried out concerning the different yeast species involved in spontaneous fermentations of Ribeiro wine. The results revealed the presence of 15 species belonging to 7 genera: Saccharomyces, Torulaspora, Dekkera, Saccharomycodes, Debaryomyces, Kloeckera and Candida. Within the genus Candida a high number of species was detected. The 28 isolated strains of S. cerevisiae showed with some exceptions, a remarkable sporulation ability and viability of the meiotic products. All the strains were homothallic. Among all S. cerevisiae strains, 6 exhibited killer K2 activity with higher isolation percentages in intermediate fermentations than in late fermentations.

Fermentation↗
PubMed1990

[Evolution of the yeast microflora during the first days of fermentation in inoculated Majorcan musts].

Three fermentations were carried out with grape must of the Callet variety. This cultivar is considered autochthonous from the island of Majorca. Two tanks were inoculated with starting cultures of selected yeasts and the last was fermented spontaneously by wild yeasts. The frequency of yeast isolates during the early stages of the fermentation, showed that Candida stellata was more affected by the inoculation than the other wild yeasts with the exception of Saccharomyces cerevisiae. The chemical analyses of wines showed a better alcoholic rate and less volatile acidity in the inoculated wines. Two sensorial analyses were performed and significant differences between the wines were noted.

Fermentation↗
PubMed2026

Microbial diversity, functional activities, and safety risks in fermented tea: a comprehensive review.

Microbial fermented teas are gaining global popularity due to their unique sensory profiles and health benefits. The quality and safety of these products are governed by complex microbial ecosystems that orchestrate the biotransformation of tea leaf components. This review addresses a critical paradox in the field: the same microbial activities that generate desirable bioactive metabolites, such as theabrownins and organic acids, also create ecological niches for mycotoxigenic fungi, posing significant health risks from contaminants like ochratoxin A, citrinin, and aflatoxins. While extensive research has cataloged the microbial diversity in these systems, a comprehensive framework linking processing environments to microbial community assembly, functional outcomes, and quantifiable safety risks remains elusive. This review systematically bridges this gap by synthesizing current knowledge on the microbial consortia-dominated by Aspergillus, Penicillium, Bacillus, and Lactiplantibacillus species-that drive tea fermentation. We critically analyze their functional roles in enhancing flavor, bioactivity, and potential probiotic activity while simultaneously evaluating the mechanisms of mycotoxin production and accumulation. By integrating microbial ecology, biochemistry, and food safety, we propose a forward-looking perspective focused on transitioning the industry from traditional, spontaneous fermentation to modern, controlled biotechnological processes. This approach, centered on the use of defined starter cultures, predictive modeling, and active biocontrol strategies, provides a roadmap for ensuring the consistent quality and safety of fermented tea products, ultimately unlocking their full potential as high-quality functional foods.

Tea↗
PubMedDate not supplied

[Spontaneous crystallization of antibiotic substance during submerged fermentation of Actinomyces hygroscopicus].

A rare case of spontaneous crystallization of the antibiotic substance was detected during submerged cultivation of Actinomyces hygroscopicus, strain 33x, under periodic conditions directly in the MTF 5L3 fermenter ("Marubishi"). Leaf-shaped plates of the antibiotic found in the cultural broth of the strain 33x were active against gram-positive and gram-negative microorganisms, yeasts, and fungi. The crystalline state of the structures was confirmed by the X-ray analysis. According to their UV spectrum (maximum at 233-234 nm in ethanol), the crystals belong to the group of nyphimycin A1-scopafungin, antibiotics produced by some cultures of Act. hygroscopicus.

Anti-Bacterial Agents↗
PubMed1990

Simultaneous loss of N5-(carboxyethyl)ornithine synthase, nisin production, and sucrose-fermenting ability by Lactococcus lactis K1.

A spontaneous derivative of Lactococcus lactis subsp. lactis K1 (formerly Streptococcus lactis K1) lacking N5-(carboxyethyl)ornithine synthase (EC 1.5.1.24) was isolated. This mutant had also lost the abilities to ferment sucrose and to produce the antibiotic nisin. Hybridization studies indicate that these linked traits are encoded on the chromosome of L. lactis K1 and that they may be located on a conjugative transposon.

Amino Acid Oxidoreductases↗
PubMed1977

Extra-chromosomal inheritance of rhodamine 6G resistance in Saccharomyces cerevisiae.

Rhodamine 6G was found to be a specific inhibitor of aerobic growth of yeast, having no effect on fermentative growth. A single step spontaneous mutant of S. cerevisiae resistant to rhodamine 6G was isolated, which showed cross-resistance to the ATPase inhibitors venturicidin and triethyltin, to the uncoupler 1799, to bongkrekic acid and to cycloheximide, but not to oligomycin or to the inhibitors of mito chondrial protein synthesis, chloramphenicol and erythromycin. The genetic analysis of this mutant showed that both nuclear and cytoplasmic (but apparently not mitochondrial) factors may be involved in the determination of the mutation. The behaviour is discussed as a possible function for 2 micron circular (omicron) DNA.

Cross Reactions↗
PubMed1991

PDC6, a weakly expressed pyruvate decarboxylase gene from yeast, is activated when fused spontaneously under the control of the PDC1 promoter.

Three structural genes encode the pyruvate decarboxylase isoenzymes in the yeast Saccharomyces cerevisiae. PDC1 and PDC5 are active during glucose fermentation where PDC1 is expressed about six times more strongly than PDC5. Expression of PDC6 is weak and seems to be induced in ethanol medium. Consequently, pdc1 delta pdc5 delta double mutants do not ferment glucose and do not grow on glucose medium. Spontaneous mutants, derived from such a pdc1 pdc5 strain, were isolated which could again ferment glucose. They showed pyruvate decarboxylase activity due to a duplication of PDC6. The second copy of PDC6 was expressed under the control of the PDC1 promoter, which was still present in the pdc1 strain. However, the resulting PDC1-PDC6 fusion gene could only partially substitute for PDC1: to achieve normal growth and high pyruvate decarboxylase activity strains carrying PDC1-PDC6 required a functional PDC5 gene which is dispensable in a PDC1 wild-type background. Thus, expression of PDC5 depends on the state of the PDC1 locus: low in the PDC1 wild-type background and high in PDC1-PDC6 fusion strains and, as shown previously, in pdc1 mutants. The activation of PDC5 expression in PDC1-PDC6 strains may be due to particular properties of the PDC1-PDC6 fusion protein or simply to the weaker expression of PDC1-PDC6 in comparison to the wild-type PDC1 gene.

Alleles↗
PubMed1991

Novel insertion sequence IS1380 from Acetobacter pasteurianus is involved in loss of ethanol-oxidizing ability.

Acetobacter pasteurianus NCI1380, a thermophilic strain isolated from the surface culture of acetic acid fermentation, showed genetic instability to produce at high frequency spontaneous mutants which were deficient in ethanol oxidation because of the loss of alcohol dehydrogenase activity. Southern hybridization experiments with the cloned alcohol dehydrogenase-cytochrome c gene cluster as the probe showed insertion of an unknown DNA fragment into a specific position in the cytochrome c gene in most of the mutant strains. Cloning and sequencing analyses revealed that the inserted sequence was 1,665 bp in length and had a terminal inverted repeat of 15 bp. In addition, this inserted sequence was found to generate a 4-bp duplication at the inserted site upon transposition. The target site specificity was not very strict, but a TCGA sequence appeared to be preferentially used. The inserted sequence contains two long open reading frames of 461 and 222 amino acids which are overlapped and encoded by different strands. Although these open reading frames showed no homology to any protein registered in the DNA data bases, the longer open reading frame contained many basic amino acids (87 of 461), as was observed with transposases of so-called insertion sequence (IS) elements. All of these characteristics are typical of IS elements, and the sequence was named IS1380. The copy number of IS1380 in a cell of A. pasteurianus NCI1380 was estimated to be about 100. Several strains of acetic acid bacteria also contained IS1380 at high copy numbers. These results suggest that IS1380 is associated with the genetic loss of ethanol-oxidizing ability as well as the genetic instability of acetic acid bacteria in general.

Acetobacter↗
PubMed1977

Plasmids, loss of lactose metabolism, and appearance of partial and full lactose-fermenting revertants in Streptococcus cremoris B1.

The unstable ability to metabolize lactose (lac) via the phosphoenolpyruvate-phosphotransferase system (PTS) was examined in Streptococcus cremoris B1. The presence of functional lactose-specific PTS enzymes was correlated with the presence of a distinct plasmid species. Characterization of deoxyribonucleic acid extracted from lactose-positive (Lac+) S. cremoris B1 revealed two plasmids having molecular weights of 9 X 10(6) and 36 X 10(6). An acriflavine (BC1)-induced, lactose-negative (Lac-) mutant possessed no plasmids and was devoid of all three lac-specific PTS enzymes. A Lac- mutant (DA2) isolated by growing at elevated temperatures only possessed the 9 X 10(6)-dalton plasmid and also lacked the lac PTS enzymes. A spontaneous Lac- mutant possessed both the 9 X 10(6)-and 36 X 10(6)-dalton plasmids. This mutant displayed FIII-lac and phospho-beta-D-galactosidase (P-beta-gal) activity but was deficient in EII-lac activity. The spontaneous Lac- strain reverted to both full and partial lactose-fermenting phenotypes having FIII-lac, EII-lac, and P-beta-gal activities. BC1 and DA2 Lac- mutants reverted only to the partial lactose-fermenting phenotype having P-beta-gal activity; EII-lac and FIII-lac activities were absent. The results indicate that the genetic determinants for EII-lac, FIII-lac, and P-beta-gal are located on the 36 X 10(6)-dalton plasmid in S. cremoris B1. Evidence for a second chromosomally associated P-beta-gal gene operating in the partial lactose-fermenting revertants is also presented.

DNA, Bacterial↗
PubMed1990

A study on mass culture of Panax quinquefolium cells.

By omitting the component NH4NO3 and doubling the amount of KNO3 in MS medium, the Panax quinque folium cells cultured in such medium grew more rapidly and their saponin content was much higher than that cultured in regular MS medium. The growth rate and saponin content of the cells cultured in such medium (KNO33300 mg/l) increased 65.1% and 166.2% respectively as compared with that cultured in the regular medium. The application of oligosaccharins from Panax ginseng and Dendrobium candidum also increased their saponin content and growth rate. Especially, the content of Rg group saponins was apparently raised. It took more than 25 days for the cell suspension cultures to produce saponins in large amounts. The curve of saponin formation lagged slightly behind the growth curve in cell suspension culture and fermentation culture. The cell fermentation culture with a stabilized pH value was better than the culture with the pH value changing spontaneously on saponin content, growth rate and biomass. Finally, the culture patterns of P. quinque folium cells were compared and discussed.

Cells, Cultured↗
PubMed1990

Characterization and nucleotide sequence of the cryptic cel operon of Escherichia coli K12.

Wild-type Escherichia coli are not able to utilize beta-glucoside sugars because the genes for utilization of these sugars are cryptic. Spontaneous mutations in the cel operon allow its expression and enable the organism to ferment cellobiose, arbutin and salicin. In this report we describe the structure and nucleotide sequence of the cel operon. The cel operon consists of five genes: celA, whose function is unknown; celB and celC which encode phosphoenolpyruvate-dependent phosphotransferase system enzyme IIcel and enzyme IIIcel, respectively, for the transport and phosphorylation of beta-glucoside sugars; celD, which encodes a negative regulatory protein; and celF, which encodes a phospho-beta-glucosidase that acts on phosphorylated cellobiose, arbutin and salicin. The mutationally activated cel operon is induced in the presence of its substrates, and is repressed in their absence. A comparison of proteins encoded by the cel operon with functionally equivalent proteins of the bgl operon, another cryptic E. coli gene system responsible for the catabolism of beta-glucoside sugars, revealed no significant homology between these two systems despite common functional characteristics. The celD and celF encoded repressor and phospho-beta-glucosidase proteins are homologous to the melibiose regulatory protein and to the melA encoded alpha-galactosidase of E. coli, respectively. Furthermore, the celC encoded PEP-dependent phosphotransferase system enzyme IIIcel is strikingly homologous to an enzyme IIIlac of the Gram-positive organism Staphylococcus aureus. We conclude that the genes for these two enzyme IIIs diverged much more recently than did their hosts, indicating that E. coli and S. aureus have undergone relatively recent exchange of chromosomal genes.

Amino Acid Sequence↗
PubMed1989

Escherichia coli derivatives lacking both alcohol dehydrogenase and phosphotransacetylase grow anaerobically by lactate fermentation.

Escherichia coli mutants lacking alcohol dehydrogenase (adh mutants) cannot synthesize the fermentation product ethanol and are unable to grow anaerobically on glucose and other hexoses. Similarly, phosphotransacetylase-negative mutants (pta mutants) neither excrete acetate nor grow anaerobically. However, when a strain carrying an adh deletion was selected for anaerobic growth on glucose, spontaneous pta mutants were isolated. Strains carrying both adh and pta mutations were observed by in vivo nuclear magnetic resonance and shown to produce lactic acid as the major fermentation product. Various combinations of adh pta double mutants regained the ability to grow anaerobically on hexoses, by what amounts to a homolactic fermentation. Unlike wild-type strains, such adh pta double mutants were unable to grow anaerobically on sorbitol or on glucuronic acid. The growth properties of strains carrying various mutations affecting the enzymes of fermentation are discussed in terms of redox balance.

Acetyltransferases↗
PubMed1992

Relationships between plasma composition and parotid salivary composition and secretion rates in the potoroine marsupials, Aepyprymnus rufescens and Potorous tridactylus.

Parotid salivation was investigated in two species of potoroine marsupial, Aepyprymnus rufescens and Potorous tridactylus to ascertain flow rates and composition, the buffer capacity of the saliva with respect to possible dependence of these animals on foregut fermentation, and the similarity of anion excretion patterns to those of the kangaroo parotid. Under anaesthesia neither species secreted spontaneously and secretion was stimulated by intravenous infusion of carbachol, bethanechol and isoprenaline. Under cholinergic stimulation in Aepyprymnus, the concentrations of Na, Cl, HCO3 and osmolality were positively correlated with flow rate, whereas K, Mg, PO4, H+ and urea were negatively correlated with flow. Amylase activity and the concentrations of protein and Ca showed no consistent relation to flow. Relative to Aepyprymnus, saliva of Potorous had much lower amylase activity and amylase activity per gram protein, lower concentrations of urea and Ca, and higher Na. Protein, K and HCO3 concentrations were similar in both species. The plasma of both species had similar electrolyte concentrations, but Potorous had lower protein, urea, osmolality and amylase activity. Plasma amylase activity in Aepyprymnus rose during cholinergic stimulation to levels in excess of rodent plasma. Isoprenaline infusion in Aepyprymnus increased salivary amylase activity and concentrations of protein, Ca, HCO3 and PO4, and reduced the concentrations of Cl and H+. The patterns of anion excretion in the two potoroine marsupials were dissimilar to those of the kangaroo parotid suggesting that parotid fluid secretion is not HCO3 driven to the same extent as that of Kangaroos. Buffer anion concentrations and secretion rates were similar to koalas and low relative to kangaroos, indicating that these potoroines do not rely on foregut fermentation.

Amylases↗
PubMedDate not supplied

[Physiological properties of Saccharomyces cerevisiae during sine-modulated and stepwise changes in the medium pH].

The responses of a chemostat Saccharomyces cerevisiae culture (D = 0.1 h-1) to a stepwise increase or decrease in the pH of the medium were shown to be asymmetric. When the pH was lowered from 6.5 to a value above 0.3, the rates of oxygen uptake and carbon dioxide evolution rose for a sort period of time whereas the optical density of the culture fell down. The detected changes in the properties of the culture were identical with those which had been observed in the course of spontaneous undamped oscillations in the physiological parameters of the continuous C. cerevisiae culture. Apparently, in both cases, the energy status of cells changed when the oxidative type of metabolism was substituted by fermentation. When the pH of the medium was elevated within the same range (4.7-6.5), the response of the culture was three times as low and its properties changed in the opposite direction. When the pH of the medium was changed in a cyclic sinusoidal manner, oscillations in the physiological characteristics of the culture, identical with spontaneous oscillations were induced at certain values of the amplitude and the frequency of pH changes.

Culture Media↗
PubMedDate not supplied

[Formation of purple membranes during salt bacteria cultivation].

Experiments have been carried out on cultivation of halophile with probe selection in the interval of 1--2 hours to record the spectra of repeated disturbed completed inner reflection. Periodicity in the changes of spectral characteristics of the culture with the interval of 20--24 hours is revealed. A clearly expressed dichroism of the amid II band of the membrane complex is found, the absence of this dichroism in the protein isolated from the membrane complex is stated. It is suggested that dichroism revealed is a specific feature of the presence of purpuric membranes in the cells. Spontaneous plane orientation of protein macromolecules in purpuric membranes is established. The level of dichroism of amid II band is shown to depend on fermentation conditions of salt bacteria.

Bacteriorhodopsins↗