RESUMEN
Gamma aminobutyric acid (GABA) is a non-protein amino acid that is widely distributed in nature and its physiological importance goes beyond its role as an inhibitory neurotransmitter of the central nervous system in mammals. Since microbial fermentation is one of the most promising methods to obtain GABA, the production of this metabolite by several strains of lactic acid bacteria isolated from quinoa and amaranth sourdoughs was investigated. Lactobacillus brevis CRL 2013 produced the highest GABA levels, reaching 265 mM when optimal culture conditions were set up. The fermentative profile showed that CRL 2013 was able to catabolize carbohydrates through the phosphoketolase pathway yielding variable amounts of lactic acid, acetate and ethanol, which depended on the type of carbon source available and the presence of external electron acceptors such as fructose. Enhanced growth parameters and low GABA synthesis were associated to pentose fermentation. This impairment on GABA production machinery was partially overpassed by the addition of ethanol to the culture media. These results support the potential use of L. brevis CRL 2013 as a starter culture for the manufacture of GABA-enriched functional foods and provide further insights to the understanding of the GAD system regulation in lactic acid bacteria.
Asunto(s)
Pan/microbiología , Metabolismo de los Hidratos de Carbono/fisiología , Fermentación/fisiología , Levilactobacillus brevis/metabolismo , Ácido gamma-Aminobutírico/biosíntesis , Acetatos/metabolismo , Amaranthus/microbiología , Carbohidratos , Chenopodium quinoa/microbiología , Medios de Cultivo/metabolismo , Etanol/metabolismo , Ácido Láctico/metabolismoRESUMEN
Selenium (Se), which is present as SeCys in seleno-proteins, is involved in cancer prevention, thyroid functioning, and pathogen inhibition. Se is incorporated in the diet through Se-containing foods. Some lactic acid bacteria (LAB) can biotransform selenite (toxic) into Se-nanoparticles (SeNPs) and Se-amino acids. To exert their beneficial properties in the host, bacteria should survive the harsh conditions of the gastrointestinal tract and during food storage. We evaluated whether selenization of LAB influenced bacterial growth and survival during gastrointestinal digestion and after storage when present in a fermented fruit juice-milk (FJM) beverage. Lactobacillus brevis CRL 2051 and Fructobacillus tropaeoli CRL 2034 were grown in MRS with and without selenite, and used to inoculate the FJM matrix. Selenization had no effect on LAB growth (9.54-9.9â¯log CFU/mL) in the FJM drink. The presence of SeNPs was confirmed for both selenized strains in the FJM beverage; however, the highest Se concentration (100⯵g/L) was detected for the fermented beverage with selenized L. brevis. Under storage conditions 1.1â¯log CFU/ml decrease in cell count of selenized cells of L. brevis was observed, while no effect on cell viability was detected for non-selenized L. brevis or both selenized and control cells of F. tropaeoli. Resistance of L. brevis during digestion of the fermented FJM beverage was not affected by selenization. Contrarily, an increase (1â¯log CFU/mL) in the resistance of F. tropaeoli was observed when cells were selenized. After digestion, Se was detected in the soluble fraction of the beverage fermented by both strains, being higher for L. brevis (23.6⯵g/L). Although selenization did not exert a drastic effect on strains´ survival during storage and digestion, microbial selenization previous to food fermentation could be an interesting tool for Se enrichment avoiding thus the addition of toxic Se salts.
Asunto(s)
Digestión , Fermentación , Lactobacillales/metabolismo , Selenio/metabolismo , Animales , Bebidas/microbiología , Alimentos Fermentados/microbiología , Almacenamiento de Alimentos , Concentración de Iones de Hidrógeno , Levilactobacillus brevis/aislamiento & purificación , Levilactobacillus brevis/metabolismo , Leuconostocaceae/aislamiento & purificación , Leuconostocaceae/metabolismo , Nanopartículas del Metal/química , Microscopía Electrónica de Rastreo , Leche/microbiología , Modelos BiológicosRESUMEN
UNLABELLED: In this study, yeasts and lactic acid bacteria (LAB) were isolated from coffee fruits and identified via biochemical and molecular approaches. The isolates represented the Pichia, Debaryomyces, Candida, Clavispora, Yarrowia, Sporobolomyces, Klyveromyces, Torulaspora and Lactobacillus genera. Four isolates, namely Pichia fermentans LPBYB13, Sporobolomyces roseus LPBY7E, Candida sp. LPBY11B and Lactobacillus brevis LPBB03, were found to have the greatest antagonist activity against an ochratoxigenic strain of Aspergillus westerdijkiae on agar tests and were selected for further characterization. Applications of P. fermentans LPBYB13 in coffee cherries artificially contaminated with A. westerdijkiae showed efficacy in reducing ochratoxin A (OTA) content up to 88%. These results highlight that P. fermentans LPBYB13 fulfils the principle requirements of an efficient biological control of aflatoxigenic fungi in coffee beans and may be seen as a reliable candidate for further validation in field conditions. SIGNIFICANCE AND IMPACT OF THE STUDY: Studies based on microbial ecology and antagonistic interactions are important for the development of new strategies in controlling aflatoxin contamination of crops and are relevant to further biotechnological applications. This study shows that coffee fruit is a potential source for the isolation of microbial strains with antifungal ability. A new yeast strain, Pichia fermentans LPBYB13, showed efficacy in reducing growth and ochratoxin A production of Aspergillus westerdijkiae in coffee beans. Our results should encourage the use of this yeast strain on a large scale for biocontrol of aflatoxigenic fungi in coffee beans.
Asunto(s)
Aflatoxinas/biosíntesis , Antifúngicos/aislamiento & purificación , Aspergillus/crecimiento & desarrollo , Agentes de Control Biológico/aislamiento & purificación , Café/microbiología , Contaminación de Alimentos/prevención & control , Ocratoxinas/biosíntesis , Agentes de Control Biológico/metabolismo , Candida/aislamiento & purificación , Candida/metabolismo , Frutas/microbiología , Ácido Láctico/metabolismo , Levilactobacillus brevis/aislamiento & purificación , Levilactobacillus brevis/metabolismo , Pichia/aislamiento & purificación , Pichia/metabolismoRESUMEN
The objective of this study was to evaluate the changes in oligosaccharides and isoflavone aglycone content in soymilk during fermentation with commercial kefir culture. Soymilk was fermented with kefir culture at 25 °C for 30 h. The counts of lactic acid bacteria, Lactococcus lactis, Leuconostoc sp and yeasts; measurements of pH, acidity, α-galactosidase and ß-glucosidase activity, sugar and isoflavone contents were performed at the intervals of time. In the fermented soymilk, the lactic acid bacteria counts increased from 7.6 log to 9.1 CFU g(-1), pH reached to 4.9 and lactic acid reached 0.34 g 100 g(- 1). The α-galactosidase was produced (0.016 AU g(-1)) with 100% raffinose and 92% stachyose hydrolysis being observed after the depletion of galactose, glucose and sucrose. Kefir culture produced ß-glucosidase (0.0164 AU g(-1)), resulting in 100% bioconversion of glycitin and daidzin and 89% bioconversion of genistin into the corresponding aglycones. The fermented soymilk presented 1.67 µmol g(-1) of daidzein, 0.28 µmol g(-1) of glicitein and 1.67 µmol g (-1) of genistein.
Asunto(s)
Productos Lácteos Cultivados/química , Fermentación , Isoflavonas/química , Oligosacáridos/química , Leche de Soja/química , beta-Glucanos/química , Supervivencia Celular , Recuento de Colonia Microbiana , Manipulación de Alimentos , Microbiología de Alimentos , Genisteína/química , Concentración de Iones de Hidrógeno , Hidrólisis , Levilactobacillus brevis/metabolismo , Lactococcus lactis/metabolismo , Leuconostoc/metabolismo , Rafinosa/química , Saccharomyces cerevisiae/metabolismo , alfa-Galactosidasa/metabolismo , beta-Glucosidasa/metabolismoRESUMEN
Mezcal is an alcoholic beverage obtained from the distillation of fermented juices of cooked Agave spp. plant stalks (agave must), and each region in Mexico with denomination of origin uses defined Agave species to prepare mezcal with unique organoleptic characteristics. During fermentation to produce mezcal in the state of Tamaulipas, not only alcohol-producing yeasts are involved, but also a lactic acid bacterial community that has not been characterized yet. In order to address this lack of knowledge on this traditional Mexican beverage, we performed a DGGE-16S rRNA analysis of the lactic acid bacterial diversity and metabolite accumulation during the fermentation of a typical agave must that is rustically produced in San Carlos County (Tamaulipas, Mexico). The analysis of metabolite production indicated a short but important malolactic fermentation stage not previously described for mezcal. The denaturing gradient gel electrophoresis (DGGE) analysis of the 16S rRNA genes showed a distinctive lactic acid bacterial community composed mainly of Pediococcus parvulus, Lactobacillus brevis, Lactobacillus composti, Lactobacillus parabuchneri, and Lactobacillus plantarum. Some atypical genera such as Weissella and Bacillus were also found in the residual must. Our results suggest that the lactic acid bacteria could strongly be implicated in the organoleptic attributes of this traditional Mexican distilled beverage.
Asunto(s)
Agave/microbiología , Bebidas Alcohólicas/microbiología , Bacillus/aislamiento & purificación , Ácido Láctico/metabolismo , Lactobacillales/aislamiento & purificación , Bacillus/clasificación , Bacillus/genética , Bacillus/metabolismo , Secuencia de Bases , Dermatoglifia del ADN , ADN Ribosómico/análisis , Electroforesis en Gel de Gradiente Desnaturalizante , Fermentación , Microbiología de Alimentos , Lactobacillales/clasificación , Lactobacillales/genética , Lactobacillales/metabolismo , Lactobacillus/clasificación , Lactobacillus/genética , Lactobacillus/aislamiento & purificación , Lactobacillus/metabolismo , Levilactobacillus brevis/clasificación , Levilactobacillus brevis/genética , Levilactobacillus brevis/aislamiento & purificación , Levilactobacillus brevis/metabolismo , Lactobacillus plantarum/clasificación , Lactobacillus plantarum/genética , Lactobacillus plantarum/aislamiento & purificación , Lactobacillus plantarum/metabolismo , México , Pediococcus/clasificación , Pediococcus/genética , Pediococcus/aislamiento & purificación , Pediococcus/metabolismo , Filogenia , Reacción en Cadena de la Polimerasa , ARN Bacteriano/genética , ARN Ribosómico 16S/análisis , Weissella/clasificación , Weissella/genética , Weissella/aislamiento & purificación , Weissella/metabolismoRESUMEN
Fungal spoilage is the main cause of economic loss in the baking industry. In this study, we developed a ready-to-use biopreserver (slurry [SL]) for nonsliced packed bread by using selected antifungal lactic acid bacteria (LAB) and low-cost ingredients that are compatible with the food matrix. Four LAB strains (Lactobacillus brevis CRL 772, L. brevis CRL 796, L. plantarum CRL 778, and L. reuteri CRL 1100) tested in bread preservation were able to inhibit Penicillium sp. growth and lengthen shelf life twofold with respect to breads prepared using only Saccharomyces cerevisiae (2 days shelf life). The best biopreservation effect (5 days shelf life) was obtained with 40% antifungal slurry SL778 containing L. plantarum CRL 778; this was as effective as 0.2% calcium propionate (PCa). The antifungal effect of SL778 was related to the synthesis of acetic and phenyllactic acid as well as lactic acid, which was produced at a high concentration (31.2 mmol/kg) and lowered the pH of the dough, favoring the undissociated fraction of the organic acids. The combination of the starter SL778 with 0.4% PCa extended the shelf life of packaged bread to 24 days, 2.6-fold longer than breads prepared with only 0.4% PCa.