RESUMEN
Leuconostoc pseudomesenteroides belongs to a group of lactic acid bacteria normally isolated from fruits, which has the capacity to produce exopolysaccharides (EPS). The present study aimed to optimize the EPS production of L. pseudomesenteroides JF17, isolated from juçara fruits (palm trees threatened with extinction in the Atlantic Forest), using the response surface methodology (RSM), besides evaluating the fermentation kinetics. The maximum production of EPS 53.77 mg/mL was obtained under ideal conditions of MRS broth supplemented with sucrose at 18%, w/v, fermentation temperature of 20 °C and initial pH of 7.30. The Luedeking-Piret model suggested that the production of EPS by the JF17 strain appeared to be associated with the cell growth of the microorganism, in addition to having high efficiency in the production of the polysaccharide from the substrate (Yp/s = 17.85 ± 0.74 mg EPS/log CFU ). Thus, the ideal optimization conditions and kinetic parameters can be useful for increasing the scale up of the fermentation process in the industrial production of EPS by L. pseudomesenteroides JF17.
Asunto(s)
Leuconostoc/metabolismo , Polisacáridos/biosíntesis , Fermentación , Bosques , Concentración de Iones de Hidrógeno , TemperaturaRESUMEN
The use of lactic bacteria in the development of functional foods has increased in recent years. In addition to their probiotic characteristics, they can ferment a variety of substrates, such as cereals, roots, and tubers. Phytase producer lactic acid bacteria strains and their behavior during the fermentation process of yam-based food were studied. Leuconostoc lactis CCMA 0415, Lactobacillus plantarum CCMA 0744, and Lactobacillus fermentum CCMA 0745 were selected due to phytase production, pH reduction, and growth during 24 h of fermentation. Oxalate activity was not detected in all assays, suggesting its concentration was reduced due to the bleaching process. Among the selected strains, L. lactis CCMA 0415 appeared to be a promising strain in yam-based fermentations because it maintained a cell viability above 8 log CFU/mL and did not reduce diosgenin concentrations (around 8.0 µg/mL) after fermentation for 24 h, thereby, generating a potentially functional yam food. Furthermore, this strain promoted the decrease of pH value from 6.1 to 3.8 and produced 8.1 g/L lactic acid, at 6 h of fermentation. The L. lactis CCMA 0415 was reported as a starter culture in fermented products based on cereals, roots, and tubers.
Asunto(s)
Dioscorea/metabolismo , Fermentación/fisiología , Alimentos Fermentados/microbiología , Lactobacillus plantarum/metabolismo , Leuconostoc/metabolismo , Limosilactobacillus fermentum/metabolismo , 6-Fitasa/biosíntesis , Alantoína/análisis , Dioscorea/microbiología , Diosgenina/análisis , Ácido Láctico/análisis , Ácido Oxálico/análisis , Compuestos Orgánicos Volátiles/análisisRESUMEN
The ability of twelve strains belonging to three Leuconostoc species (Leuconostoc mesenteroides, Leuconostoc lactis and Leuconostoc pseudomesenteroides) to grow under diverse sub-lethal technological stress conditions (cold, acidic, alkaline and osmotic) was evaluated in MRS broth. Two strains, Leuconostoc lactis Ln N6 and Leuconostoc mesenteroides Ln MB7, were selected based on their growth under sub-lethal conditions, and volatile profiles in RSM (reconstituted skim milk) at optimal and under stress conditions were analyzed. Growth rates under sub-lethal conditions were strain- and not species-dependent. Volatilomes obtained from the two strains studied were rather diverse. Particularly, Ln N6 (Ln. lactis) produced more ethanol and acetic acid than Ln MB7 (Ln. mesenteroides) and higher amounts and diversity of the rest of volatile compounds as well, at all times of incubation. For the two strains studied, most of stress conditions applied diminished the amounts of ethanol and acetic acid produced and the diversity and levels of the rest of volatile compounds. These results were consequence of the different capacity of the strains to grow under each stress condition tested.
Asunto(s)
Leuconostoc/crecimiento & desarrollo , Leche/química , Compuestos Orgánicos Volátiles/metabolismo , Acetatos/metabolismo , Animales , Bovinos , Etanol/metabolismo , Cinética , Leuconostoc/química , Leuconostoc/clasificación , Leuconostoc/metabolismo , Leche/microbiología , Compuestos Orgánicos Volátiles/análisisRESUMEN
In artisanal tanneries, the skins are immersed in cereals fermented by natural microbial flora in order to reduce the pH of the skin, an essential condition for carrying out the final step. The environmental thermal variation alters the fermentation process and affects the quality of the final product. The aim of this work was to isolate lactic acid bacteria from cereals mixture fermented in an artisanal tannery and to evaluate in vitro the acidifying activity of the strains as a first step for the formulation of a starter culture. In most samples, a prevalence of cocci (95%) was observed with respect to bacilli. The best acidifying strains were identified by phenotypic and genotypic techniques as Enterococcus faecium CRL 1943 (rapid acidification at 37 °C) and Leuconostoc citreum CRL 1945 (high acidifying activity at 18 °C). In addition, the biomass production of the selected strains was analyzed at free and controlled pH (bioreactors 1.5 L). The production of biomass was optimal at controlled pH, with a higher growth (0.5-1.1 log units). Both strains were compatible, allowing their inclusion in a mixed culture. These lactic strains could contribute to the systematization of the tanning process.
Asunto(s)
Lactobacillales/aislamiento & purificación , Lactobacillales/metabolismo , Curtiembre/métodos , Reactores Biológicos , ADN Bacteriano/genética , Grano Comestible/microbiología , Enterococcus faecium/genética , Enterococcus faecium/crecimiento & desarrollo , Enterococcus faecium/aislamiento & purificación , Enterococcus faecium/metabolismo , Fermentación , Genotipo , Concentración de Iones de Hidrógeno , Ácido Láctico/biosíntesis , Lactobacillales/genética , Lactobacillales/crecimiento & desarrollo , Leuconostoc/genética , Leuconostoc/crecimiento & desarrollo , Leuconostoc/aislamiento & purificación , Leuconostoc/metabolismo , Fenotipo , ARN Ribosómico 16S/genética , Análisis de Secuencia de ADN , TemperaturaRESUMEN
BACKGROUND: Serrano Catarinense cheese is a raw bovine milk cheese produced in the region of Santa Catarina, Brazil. Twelve representative strains of Leuconostoc isolated from 20 samples of this artisanal cheese were selected and submitted for evaluation of the acidifying, proteolytic, autolytic, aminopeptidase and lipolytic activities, NaCl and acid resistance, production of dextran and biogenic amines and antimicrobial activity. The aim was to genetically and technologically characterize the Leuconostoc strains in order to use them in mixed starter cultures for cheese manufacture. RESULTS: Leuconostoc mesenteroides subsp. mesenteroides was the species that accounted for the largest proportion of isolates of Leuconostoc genus. Two leuconostoc isolates stood out in the acidifying activity, with reduction in pH of 1.12 and 1.04 units. The isolates showed low proteolytic and autolytic activity. Most of the isolates were dextran producers, presented good resistance to the salt and pH conditions of the cheese and showed antimicrobial activity against cheese pathogen bacteria, and none of them produced biogenic amines. CONCLUSION: These results allowed the selection of five strains (UEL 04, UEL 12, UEL 18, UEL 21 and UEL 28) as good candidates for use as adjunct cultures for cheese manufacture. © 2018 Society of Chemical Industry.
Asunto(s)
Queso/microbiología , Leuconostoc/metabolismo , Animales , Aminas Biogénicas/análisis , Aminas Biogénicas/metabolismo , Brasil , Bovinos , Queso/análisis , Fermentación , Leuconostoc/genética , Leuconostoc/aislamiento & purificación , Leche/microbiologíaRESUMEN
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
OBJECTIVES: to identify characteristics related to the interruption of nurses in professional practice, as well as to assess the implications of interruptions for patient safety. METHOD: integrative literature review. The following databases were searched: Pubmed/Medline, LILACS, SciELO and Cochrane Library, using the descriptors interruptions and patient safety. An initial date was not established, but the final date was December 31, 2013. A total of 29 papers met the inclusion criteria. RESULTS: all the papers included describe interruptions as a harmful factor for patient safety. Data analysis revealed three relevant categories: characteristics of interruptions, implications for patient safety, and interventions to minimize interruptions. CONCLUSION: interruptions favor the occurrence of errors in the health field. Therefore, there is a need for further studies to understand such a phenomenon and its effects on clinical practice. .
OBJETIVOS: identificar características relacionadas à interrupção de enfermeiros em sua prática profissional, bem como avaliar as implicações para a segurança do paciente. MÉTODO: foi realizada revisão de literatura do tipo integrativa, com busca nas bases de dados Pubmed/Medline, LILACS, SciELO e Biblioteca Cochrane, utilizando os descritores interruptions e patient safety. A data inicial não foi limitada e a data final foi 31 de dezembro de 2013, identificando-se 29 artigos que atenderam aos critérios de inclusão. RESULTADOS: todos os artigos revisados descreveram a interrupção como fator prejudicial à segurança do paciente. A análise destes estudos revelou três categorias relevantes: características da interrupção, implicações da interrupção para a segurança do paciente e intervenções para minimizar as interrupções. CONCLUSÃO: a interrupção favorece a ocorrência de erros na saúde. Assim, notou-se necessidade de novas pesquisas para compreender tal fenômeno e seus efeitos na prática clínica. .
OBJETIVOS: identificar características relacionadas a la interrupción que sufren los enfermeros en su práctica profesional, así como evaluar las implicaciones para la seguridad del paciente. MÉTODO: fue realizada una revisión de literatura de tipo integradora, con búsqueda en las bases de datos Pubmed/Medline, LILACS, SciELO y Biblioteca Cochrane, utilizando los descriptores interruptions y patient safety. La fecha inicial no fue limitada y la fecha final fue 31 de diciembre de 2013, se identificaron 29 artículos que atendieran a los criterios de inclusión. RESULTADOS: todos los artículos revisados describieron la interrupción como un factor perjudicial a la seguridad del paciente. El análisis de estos estudios reveló tres categorías relevantes: características de la interrupción, implicaciones de la interrupción para la seguridad del paciente e intervenciones para minimizar las interrupciones. CONCLUSIÓN: la interrupción favorece la ocurrencia de errores en la salud. Así, se notó la necesidad de realizar nuevas investigaciones para comprender ese fenómeno y los efectos del mismo en la práctica clínica. .
Asunto(s)
Animales , Bacteriocinas/biosíntesis , Clima Desértico , Leuconostoc/aislamiento & purificación , Leuconostoc/metabolismo , Leche/química , Leche/microbiología , Proteómica/métodos , Argelia , Antiinfecciosos/farmacología , Bacterias/efectos de los fármacos , Camelus , Fermentación/efectos de los fármacos , Pruebas de Sensibilidad Microbiana , Fenotipo , Filogenia , Especificidad de la Especie , Espectrometría de Masa por Láser de Matriz Asistida de Ionización DesorciónRESUMEN
The production of bacteriocins by Leuconostoc mesenteroides represents an important opportunity for exploration of their potential use for industrial purpose. The antimicrobial compounds produced by L. mesenteroides subsp. mesenteroides SJRP55 strain were characterized and purified. Cell-free supernatant of Leuc. mesenteroides subsp. mesenteroides SJRP55 produced antibacterial compounds against Listeria spp. strains and not inhibiting against Lactobacillus spp. The antimicrobial substances were stable at high temperatures (100 °C for 2 h and 121 °C for 20 min) and low pH (pH 2-4) values, but sensitive to proteolytic enzymes and resistant to α-amylase, lipase and catalase enzymes. The optimal temperature for active peptides production was 25 °C. The antimicrobial compounds were purified by ammonium sulfate precipitation, affinity column and reverse-phase chromatography. Mass spectrometry and amino acids analyses showed that the bacteriocins were identical to mesentericin Y105 and B105. The producer strain's DNA analysis revealed presence of open reading frames possibly coding for virulence factors, such as enterococcal surface protein (esp), collagen adhesion (ace) and intrinsic vancomycin resistance (vanA); however, biogenic amines encoding genes were not observed. Leuc. mesenteroides subsp. mesenteroides SJRP55 is a promising biopreservative culture in fermented milk, and the purified bacteriocins can also be applied in food preservation.
Asunto(s)
Bacteriocinas/biosíntesis , Queso/microbiología , Leuconostoc/aislamiento & purificación , Animales , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Bacteriocinas/química , Brasil , Bovinos , Leuconostoc/clasificación , Leuconostoc/genética , Leuconostoc/metabolismo , Espectrometría de Masas , Leche/microbiologíaRESUMEN
Cell-free supernatant from Leuconostoc citreum MB1 revealed specific antilisterial activity. Preliminary studies demonstrated the proteinaceous, heat-stable, bacteriocin-like trait of the antimicrobial components present in the supernatant. Determination of the genes encoding bacteriocins by PCR and DNA sequencing led to amplification products highly homologous with leucocin A (found in diverse Leuconostoc species) and UviB (found in Leuc. citreum KM20) sequences. Additionally, antimicrobial activity of cell-free supernatant from Leuc. citreum MB1 was revealed by an inhibition halo of the SDS-PAGE gel subjected to a direct detection using Listeria monocytogenes as indicator strain. Different assays were carried out to assess the capacity of Leuc.citreum MB1 to control List. monocytogenes growth: (i) inactivation kinetics of the pathogen by antilisterial compounds present in concentrated cell-free supernatant from Leuc. citreum MB1, (ii) evaluation of optimal Leuc. citreum MB1 initial concentration to obtain maximum List. monocytogenes ATCC 15313 inhibition, and (iii) biocontrol of List. monocytogenes ATCC 15313 with Leuc. citreum MB1 during growth in milk at refrigeration temperature. According to our results, it is unquestionable that at least one bacteriocin is active in Leuc. citreum MB1, since important antilisterial activity was verified either in its cell-free supernatant or in co-culture experiments. Co-culture tests showed that â¼107 CFU/ml Leuc. citreum MB1 was the optimal initial concentration to obtain maximum pathogen inhibition. Moreover, Leuc. citreum MB1 was able to delay List. monocytogenes growth at refrigerated temperature.
Asunto(s)
Bacteriocinas/farmacología , Agentes de Control Biológico , Leuconostoc/metabolismo , Listeria monocytogenes/efectos de los fármacos , Leche/microbiología , Animales , Bacteriocinas/genética , Secuencia de Bases , Técnicas de Cocultivo , Frío , Recuento de Colonia Microbiana , Medios de Cultivo Condicionados/química , ADN Bacteriano/química , Electroforesis en Gel de Poliacrilamida , Leuconostoc/genética , Listeria monocytogenes/crecimiento & desarrollo , Datos de Secuencia Molecular , Reacción en Cadena de la Polimerasa , Homología de SecuenciaRESUMEN
The effect of high pressure homogenization (HPH) with respect to a traditional heat treatment on the inactivation, growth at 8°C after treatments, and volatile profile of adventitious Leuconostoc strains isolated from Cremoso Argentino spoiled cheeses and ingredients used for their manufacture was evaluated. Most Leuconostoc strains revealed elevated resistance to HPH (eight passes, 100 MPa), especially when resuspended in skim milk. Heat treatment was more efficient than HPH in inactivating Leuconostoc cells at the three initial levels tested. The levels of alcohols and sulfur compounds increased during incubation at 8°C in HPH-treated samples, while the highest amounts of aldehydes and ketones characterized were in heated samples. Leuconostoc cells resuspended in skim milk and subjected to one single-pass HPH treatment using an industrial-scale machine showed remarkable reductions in viable cell counts only when 300 and 400 MPa were applied. However, the cell counts of treated samples rose rapidly after only 5 days of storage at 8°C. The Leuconostoc strains tested in this work were highly resistant to the inactivation treatments applied. Neither HPH nor heat treatment assured their total destruction, even though they were more sensitive to the thermal treatment. To enhance the inhibitory effect on Leuconostoc cells, HPH should be combined with a mild heat treatment, which in addition to efficient microbial inactivation, could allow maximal retention of the physicochemical properties of the product.
Asunto(s)
Queso/microbiología , Manipulación de Alimentos/métodos , Calor , Leuconostoc/fisiología , Presión , Recuento de Colonia Microbiana , Contaminación de Alimentos/análisis , Microbiología de Alimentos , Conservación de Alimentos/métodos , Tecnología de Alimentos/métodos , Humanos , Leuconostoc/crecimiento & desarrollo , Leuconostoc/metabolismo , Viabilidad Microbiana , Factores de TiempoRESUMEN
The genus Leuconostoc belongs to a group of lactic acid bacteria usually isolated from fermented vegetables, which includes species involved in the production of exopolysaccharides (EPS). These biopolymers possess considerable commercial potential. Because of the wide variety of industrial applications of EPS, this study aimed to produce and characterize the native exopolysaccharide strain Leuconostoc pseudomesenteroides R2, which was isolated from cabbage collected in a semi-arid region of Bahia. We employed the following conditions for the production of EPS: 10.7% sucrose, pH 8.2, without agitation and incubation at 28ºC for 30 hours. The fermentation broth was treated with ethanol and generated two types of polysaccharide substances (EPS I and EPS II). The identification of EPS I and EPS II was conducted using FT-IR, (1)H, (13)C and DEPT-135 NMR spectra. The two substances were identified as linear dextran α polysaccharides (1 â 6) which indicated different characteristics with respect to thermal analysis and density of free packaging, viscosity and time of solubilization. Both dextrans are of low density, possess high thermal stability and exhibited the behavior characteristic of pseudoplastic polymers.
Asunto(s)
Brassica/microbiología , Leuconostoc/metabolismo , Polisacáridos Bacterianos/biosíntesis , Fermentación , Espectroscopía de Resonancia Magnética , Polisacáridos Bacterianos/aislamiento & purificación , ViscosidadRESUMEN
Sugar concentration from sugarcane juice and yeast autolysate increased lactic acid production more than the other agro-industrial substrates tested. The concentrations of these two components were further optimized using the Plackett-Burman design and response surface method. A second-order polynomial regression model estimated that a maximal lactic acid production of 66.11 g/L would be obtained when the optimal values of sugar and yeast autolysate were 116.9 and 44.25 g/L, respectively. To validate the optimization of the medium composition, studies were carried out using the optimized conditions to confirm the result of the response surface analysis. After 48 h, lactic acid production using the shake-flask method was at 60.2 g/L.
Asunto(s)
Carbono/metabolismo , Microbiología Industrial/métodos , Ácido Láctico/biosíntesis , Leuconostoc , Nitrógeno/metabolismo , Algoritmos , Extractos Celulares , Medios de Cultivo/química , Fermentación , Leuconostoc/crecimiento & desarrollo , Leuconostoc/metabolismo , Modelos Estadísticos , Melaza , Saccharum/metabolismo , Levaduras/metabolismoRESUMEN
The use of agriculture substrates in industrial biotechnological processes has been increasing because of their low cost. In this work, the use of clarified cashew apple juice was investigated as substrate for enzyme synthesis of prebiotic oligosaccharide. The results showed that cashew apple juice is a good source of reducing sugars and can be used as substrate for the production of dextransucrase by Leuconostoc citreum B-742 for the synthesis of oligosaccharides using the crude enzyme. Optimal oligosaccharide yield (approximately 80%) was obtained for sucrose concentrations lower than 60 g/L and reducing sugar concentrations higher than 100 g/L.
Asunto(s)
Agricultura/métodos , Biotecnología/métodos , Oligosacáridos/química , Anacardium , Carbohidratos/química , Industria de Alimentos , Glucosiltransferasas/química , Glicerol/química , Concentración de Iones de Hidrógeno , Leuconostoc/metabolismo , Malus , Oligosacáridos/metabolismo , Propiedades de SuperficieRESUMEN
dsrP, a gene that encodes a cell-associated dextransucrase produced by Leuconostoc mesenteroides IBT-PQ, was isolated, sequenced and expressed in Escherichia coli. From sequence analysis, seven repeat units in the N-terminal region were found, as well as five cell wall binding repeats in the C-terminal region. A model of the C-terminal domain of dextransucrase was built based on the solenoid structure of the cell wall binding domain already described in LytA. By experiments involving direct interactions of the enzyme with L. mesenteroides cells, as well as among the cells and the single C-terminal domain expressed in E. coli, evidence was obtained concerning the anchoring function of this region in cell-associated dextransucrase, a function which may be independent of its capacity to bind dextran.
Asunto(s)
Pared Celular/metabolismo , Glucosiltransferasas/química , Glucosiltransferasas/metabolismo , Leuconostoc/enzimología , Secuencia de Aminoácidos , Clonación Molecular , Glucosiltransferasas/genética , Leuconostoc/genética , Leuconostoc/crecimiento & desarrollo , Leuconostoc/metabolismo , Modelos Moleculares , Datos de Secuencia Molecular , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismoRESUMEN
This work was conducted to identify indigenous LAB capable of antimicrobial activity, present in traditional Mexican-foods with potential as natural preservatives. A total of 27 artisan unlabeled Mexican products were evaluated, from which 94 LAB strains were isolated, and only 25 strains showed antimicrobial activity against at least one pathogen indicator microorganism. Most of the inhibitory activity showed by the isolated LAB strains was attributed to pH reduction by organic acids. Lactobacillus and Lactococcus strains were good acid producers, depending on the substrate, and may enhance the safety of food products. Cell free cultures of Leuconostoc mesenteroides CH210, and PT8 (from chorizo and pulque, respectively) reduced the number of viable cells of enteropathogenic E. coli in broth system. Lb. plantarum CC10 (from "madre" of vinegar) showed significant inhibitory effect against S. aureus 8943. E. faecium QPII (from panela cheese) produced a bacteriocin with wide anti-L. monocytogenes activity. Selected LAB from traditional Mexican foods showed good potential as bio-preservatives.
Asunto(s)
Ácidos/metabolismo , Antiinfecciosos/metabolismo , Bacteriocinas/metabolismo , Microbiología de Alimentos , Lactobacillus/aislamiento & purificación , Lactococcus/aislamiento & purificación , Leuconostoc/aislamiento & purificación , Bebidas Alcohólicas/microbiología , Queso/microbiología , Medios de Cultivo Condicionados/farmacología , Manipulación de Alimentos/métodos , Conservación de Alimentos , Bacterias Gramnegativas/efectos de los fármacos , Bacterias Gramnegativas/crecimiento & desarrollo , Bacterias Grampositivas/efectos de los fármacos , Bacterias Grampositivas/crecimiento & desarrollo , Lactobacillus/metabolismo , Lactococcus/metabolismo , Leuconostoc/metabolismo , Productos de la Carne/microbiología , México , Pruebas de Sensibilidad MicrobianaRESUMEN
AIMS: The purpose of this work was to study the effect of L-malic and/or citric acids on Oenococcus oeni m growth in deficient nutritional conditions, and their roles as possible biosynthetic precursors of the essential amino acids. METHODS AND RESULTS: Bacterial cultures were performed in synthetic media. Bacterial growth rate was reduced or annulled when one amino acid was omitted from basal medium, especially for members of aspartate family, except lysine. The organic acids increased or restored the growth rates to the respective reference values. In each medium deficient in one essential amino acid, the L-malic acid utilization was accompanied by an increase of L-lactic acid concentration and accounted for approximately 100%l-malic acid consumed. D-lactic acid formation from glucose decreased in the medium without cysteine. Except for tyrosine, the recovery of glucose-citrate as D-lactic acid was lower than in the complete medium when asparagine, isoleucine or cysteine were excluded. The ethanol and acetate production was not modified. CONCLUSIONS: L-malic and citric acids favoured Oenococcus oeni m growth in nutritional stress conditions. Specifically citric acid was involved in the biosynthesis of the aspartate-derived essential amino acids and glucose in the cysteine biosynthesis. SIGNIFICANCE AND IMPACT OF THE STUDY: Such beneficial effect of l-malic and citric acids on amino acids requirements of Oenococcus oeni m have great significance considering the low amino acids concentration in wine.
Asunto(s)
Aminoácidos/farmacología , Ácido Cítrico/metabolismo , Cocos Grampositivos/metabolismo , Malatos/metabolismo , Vino/microbiología , Aminoácidos/biosíntesis , Medios de Cultivo/farmacología , Cocos Grampositivos/crecimiento & desarrollo , Leuconostoc/crecimiento & desarrollo , Leuconostoc/metabolismoRESUMEN
Some of the most widely used products in the food industry are flavour compounds. These products can be obtained either by chemical synthesis and therefore are called synthetic or by fermentation thus called natural flavors. There is a tendency towards the use of natural products by the consumer, therefore there is an increasing industrial interest in them. One of these products is diacetyl, an important component in the flavor of butter, although others, like acetoin, acetaldehyde and 2,3-butanediol play a role in the flavor, they are present in trace amounts. The mixture of all these compounds produced during the lactic acid fermentation in suitable proportions is what gives butter its characteristic flavor. The most common metabolic route that produces diacetyl is the one starting from pyruvate, in this case it seems that the biosynthesis is related to the presence of citrate in the medium. An alternative route for the production is from acetaldehyde, in this route citrate does not seem to intervene. In the present paper a review of the mechanisms of formation of diacetyl by lactic acid bacteria, as well as the most important factors that influence the biosynthesis of this metabolite is made.
Asunto(s)
Diacetil/metabolismo , Aditivos Alimentarios/metabolismo , Microbiología de Alimentos , Lactococcus/metabolismo , Leuconostoc/metabolismo , Productos Lácteos/microbiología , Fermentación , Concentración de Iones de Hidrógeno , Vino/microbiologíaRESUMEN
Fast lactose fermenting Leuconostoc species and subspecies were isolated from raw milk. Samples were obtained from dairy farms of the surroundings of Buenos Aires city. A lactose, non selective, isolation medium was employed (YCL). Differentiation of leuconostocs from Lactobacillus viridescens and L. confusus was avoided on account of the use of this medium. 801 typical colonies of lactic acid bacteria were selected from YCL agar; 710 of them were identified as lactic acid bacteria from which 114 strains belonged to the genus Leuconostoc. These last strains were then tested for species and subspecies differentiation by dextran production and sugar fermentation. Leuconostoc mesenteroides subsp. dextranicum and L. lactis were identified. Four strains identified as Leuconostoc spp do not belong to any known species.