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J Microbiol Biotechnol ; 29(2): 191-199, 2019 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-30602270


We inoculated different combinations of three starter candidates of Bacillus licheniformis, Staphylococcus succinus, and Tetragenococcus halophilus, into sterilized soybeans to predict their contributions to volatile compounds production through soybean fermentation. Simultaneously, we added NaCl to soybean cultures to evaluate its effect on the volatile compounds profile. Cells in soybean cultures (1.5% NaCl) reached almost their maximum growth in a day of incubation, while cell growth was delayed by increasing NaCl concentration in soybean cultures. The dominance of B. licheniformis and S. succinus in the mixed culture of three starter candidates switched to T. halophilus as the NaCl concentration increased from 1.5% to 14% (w/w). Seventeen volatile compounds were detected from the control and starter candidate-inoculated soybean cultures with and without the addition of NaCl. Principal component analysis of these volatile compounds concluded that B. licheniformis and S. succinus made major contributions to producing a specific volatile compound profile from soybean cultures where both species exhibited good growth. 3-Hydroxybutan-2-one, butane-2,3-diol, and 2,3,5,6-tetramethylpyrazine are specific odor notes for B. licheniformis, and 3-methylbutyl acetate and 2-phenylethanol are specific for S. succinus. Octan-3-one and 3-methylbutan-1-ol were shown to be decisive volatile compounds for determining the involvement of S. succinus in the soybean culture containing 7% NaCl. 3-Methylbutyl acetate and 3-methylbutan-1-ol were also produced by T. halophilus during soybean fermentation at an appropriate level of NaCl. Although S. succinus and T. halophilus exhibited growth on the soybean cultures containing 14% NaCl, species-specific volatile compounds determining the directionality of the volatile compounds profile were not produced.

Bactérias/metabolismo , Microbiologia de Alimentos , Alimentos de Soja/microbiologia , Soja/metabolismo , Compostos Orgânicos Voláteis/metabolismo , Bactérias/classificação , Bactérias/efeitos dos fármacos , Bactérias/crescimento & desenvolvimento , Fermentação , Concentração de Íons de Hidrogênio , Microbiota/efeitos dos fármacos , Análise de Componente Principal , Cloreto de Sódio/química , Cloreto de Sódio/farmacologia , Especificidade da Espécie , Compostos Orgânicos Voláteis/análise
Artigo em Inglês | MEDLINE | ID: mdl-30394048


In 2015, Bacillus paralicheniformis was separated from B. licheniformis on the basis of phylogenomic and phylogenetic studies, and urease activity was reported as a phenotypic property able to differentiate between the two species. Subsequently, we have found that the urease activity of B. paralicheniformis is strain-specific, and does not reliably discriminate between species, as strains having the same urease gene cluster were identified in B. licheniformis and B. sonorensis, the closest relatives of B. paralicheniformis. We developed a multilocus sequence typing scheme using eight housekeeping genes, adk, ccpA, glpF, gmk, ilvD, pur, spo0A, and tpi to clearly identify B. paralicheniformis from closely related Bacillus species and to find a molecular marker for the rapid identification of B. paralicheniformis. The scheme differentiated 33 B. paralicheniformis strains from 90 strains formerly identified as B. licheniformis. Among the eight housekeeping genes, spo0A possesses appropriate polymorphic sites for the design of a B. paralichenofomis-specific PCR primer set. The primer set designed in this study perfectly separated B. paralicheniformis from B. licheniformis and B. sonorensis.

Int J Food Microbiol ; 262: 8-13, 2017 Dec 04.
Artigo em Inglês | MEDLINE | ID: mdl-28950164


We inoculated five starter candidates, Enterococcus faecium, Tetragenococcus halophilus, Bacillus licheniformis, Staphylococcus saprophyticus, and Staphylococcus succinus, into sterilized soybeans to predict their effectiveness for flavor production in fermented soybean foods. All of the starter candidates exhibited sufficient growth and acid production on soybean cultures. Twenty-two volatile compounds, such as acids, alcohols, carbonyls, esters, furans, and pyrazines, were detected from the control and starter candidate-inoculated soybean cultures. Principal component analysis of these volatile compounds concluded that E. faecium and T. halophilus produced a similar profile of volatile compounds to soybeans with no dramatic differences in soybean flavor. B. licheniformis and S. succinus produced the crucial volatile compounds that distinguish the flavor profiles of soybean. During soybean fermentation, phenylmethanol and 2,3,5,6-tetramethylpyrazine were determined as odor notes specific to B. licheniformis and 3-methylbutyl acetate as an odor note specific to S. succinus.

Bactérias/metabolismo , Alimentos Fermentados/microbiologia , Alimentos de Soja/microbiologia , Soja/metabolismo , Soja/microbiologia , Compostos Orgânicos Voláteis/metabolismo , Ácidos/análise , Bactérias/classificação , Álcoois Benzílicos/análise , Fermentação , Análise de Componente Principal , Pirazinas/análise , Paladar , Compostos Orgânicos Voláteis/análise
J Microbiol Biotechnol ; 27(5): 916-924, 2017 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-28237994


Eighty-five Enterococcus faecalis isolates collected from animals (40 isolates), meju (a Korean fermented soybean product; 27 isolates), humans (10 isolates), and various environmental samples (8 isolates) were subjected to multilocus sequence typing (MLST) to identify genetic differences between samples of different origins. MLST analysis resulted in 44 sequence types (STs), and the eBURST algorithm clustered the STs into 21 clonal complexes (CCs) and 17 singletons. The predominant STs, ST695 (21.1%, 18/85) and ST694 (9.4%, 8/85), were singletons, and only contained isolates originating from meju. None of the STs in the current study belonged to CC2 or CC9, which comprise clinical isolates with high levels of antibiotic resistance. The E. faecalis isolates showed the highest rates of resistance to tetracycline (32.9%), followed by erythromycin (9.4%) and vancomycin (2.4%). All isolates from meju were sensitive to these three antibiotics. Hence, MLST uncovered genetic diversity within E. faecalis, and clustering of the STs using eBURST revealed a correlation between the genotypes and origins of the isolates.

Farmacorresistência Bacteriana/genética , Enterococcus faecalis/classificação , Enterococcus faecalis/genética , Microbiologia de Alimentos , Variação Genética , Filogenia , Soja/microbiologia , Animais , Antibacterianos/farmacologia , Bovinos , Galinhas , DNA Bacteriano/genética , Enterococcus faecalis/efeitos dos fármacos , Enterococcus faecalis/isolamento & purificação , Microbiologia Ambiental , Eritromicina/farmacologia , Fermentação , Genes Bacterianos , Genótipo , Humanos , Testes de Sensibilidade Microbiana/veterinária , Tipagem de Sequências Multilocus/métodos , Tipagem de Sequências Multilocus/veterinária , Reação em Cadeia da Polimerase , RNA Ribossômico 16S/genética , República da Coreia , Suínos , Tetraciclina/farmacologia , Vancomicina/farmacologia
Sci Rep ; 6: 35066, 2016 10 07.
Artigo em Inglês | MEDLINE | ID: mdl-27713526


In2O3 nanostructure sensors were fabricated by arc-discharging a source composed of a graphite tube containing indium. The NO gas sensing properties, as well as the morphology, structure, and electrical properties, were examined at room temperature under UV light illumination. In particular, the response and recovery kinetics of the sensor at room temperature under various UV light intensities were studied. The maximum response signal was observed at an intermediate UV light intensity, which could be corroborated by a nano-size effect based on the conduction model of a resistive chemical nano sensor. The mechanism for the enhanced adsorption/desorption kinetics for NO in an air environment under UV light irradiation is discussed in detail. Furthermore, the general requirements of the sensor, including the stability, repeatability, and selectivity, are discussed.