Lactic fermentation as a strategy to improve the nutritional and functional values of pseudocereals

One of the greatest challenges is to reduce malnutrition worldwide while promoting sustainable agricultural and food systems. This is a daunting task due to the constant growth of the population and the increasing demands by consumers for functional foods with higher nutritional values. Cereal grains are the most important dietary energy source globally; wheat, rice, and maize currently provide about half of the dietary energy source of humankind. In addition, the increase of celiac patients worldwide has motivated the development of gluten-free foods using alternative flour types to wheat such as rice, corn, cassava, soybean, and pseudocereals (amaranth, quinoa, and buckwheat). Amaranth and quinoa have been cultivated since ancient times and were two of the major crops of the Pre-Colombian cultures in Latin-America. In recent years and due to their well-known high nutritional value and potential health benefits, these pseudocereals have received much attention as ideal candidates for gluten-free products. The importance of exploiting these grains for the elaboration of healthy and nutritious foods has forced food producers to develop novel adequate strategies for their processing. Fermentation is one of the most antique and economical methods of producing and preserving foods and can be easily employed for cereal processing. The nutritional and functional quality of pseudocereals can be improved by fermentation using Lactic Acid Bacteria (LAB). This review provides an overview on pseudocereal fermentation by LAB emphasizing the capacity of these bacteria to decrease antinutritional factors such as phytic acid, increase the functional value of phytochemicals such as phenolic compounds, and produce nutritional ingredients such as B-group vitamins. The numerous beneficial effects of lactic fermentation of pseudocereals can be exploited to design novel and healthier foods or grain ingredients destined to general population and especially to patients with coeliac disease.Fil: Rollan, Graciela Celestina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; ArgentinaFil: Gerez, Carla Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; ArgentinaFil: Leblanc, Jean Guy Joseph. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; Argentin

Seitan, an ingredient in new foods and its characterization

El seitán es el gluten de trigo y se lo denomina carne vegetal por su aspecto similar a ésta. Se lo elabora mediante amasado de harina de trigo y posterior lavado, para eliminar el almidón. Luego se hierve con alga Kombu y tamari (salsa de soja) para enriquecerlo en vitaminas y minerales y tome color. Posee un alto contenido proteico, bajo en carbohidratos y grasas y, al ser un alimento de origen vegetal, no contiene colesterol. Es originario de China. Los japoneses de orientación macrobiótica lo introdujeron en Estados Unidos, principalmente a través de los Mormones y los Adventistas del Séptimo Día, alrededor de 1940. Luego se propagó entre quienes practican el vegetarianismo. La investigación se realizó en base a un tipo de estudio exploratorio-descriptivo. El estudio exploratorio se llevó a cabo a través de la elaboración artesanal de seitán y su inclusión en diferentes preparaciones alimenticias. Los productos que se elaboraron exitosamente fueron: milanesas, sfijas y kipe. Se realizó la cuantificación de macronutrientes y antioxidantes y finalmente, con los resultados obtenidos, se calculó el valor calórico por porción y por 100 g de cada producto elaborado. La cuantificación de macronutrientes indica que tanto el seitán como los productos elaborados poseen un elevado contenido proteico y, en cuanto a la valoración nutricional, las tres preparaciones presentan un alto valor calórico, siendo el kipe el de mayor calorías por cada 100 g de alimento, seguido de las sfijas y, por último, de las milanesas. El estudio descriptivo se realizó a través de encuestas, que determinaron las características organolépticas, el grado de satisfacción y la aceptabilidad, en las cuales participó un grupo de cincuenta personas, habitantes de la capital de la provincia de Tucumán. Los resultados evidenciaron que los productos elaborados con seitán son satisfactorios, poseen un alto grado de aceptación y son agradables en lo que respecta a sus características organolépticas. Con este trabajo se pretende sentar las bases para generar futuras investigaciones y, al mismo tiempo, promover la elaboración artesanal del seitán y de los alimentos preparados a partir de esta proteína vegetal, ampliando el conocimiento de la sociedad sobre la gran alternativa disponible en cuanto a su dieta habitual.Seitan is made from wheat gluten, and it is called vegetable meat due to its similarity to meat. It is made by washing wheat flour dough until all the starch has been removed. Then it is simmered in a broth of kombu seaweed and tamari (soy sauce), so as to enrich it with vitamins andminerals, and to give it color. Seitan is a low-fat, lowcarbohydrate and high-protein food. Being also a vegetablebased food, it doesn’t contain cholesterol. Originally from China, it was introduced in the United States by the Japanese people with a macrobiotic lifestyle, mainly by the Mormons and the Seventh-day Adventists, in around 1940. Then it gained popularity among vegetarians. This research was based in an exploratory-descriptive study. To carry out the exploratory study, seitan was prepared manually and used in different food preparations. The products successfully made were breaded cutlets, sfijas and kibbeh. The macronutrients and antioxidants were quantified, and these results were used to calculate the caloric value per portion and per 100 g for each food product. The macronutrient quantification reveals that both the seitan and the prepared products have high-protein content. As regards the nutritional value, the three food products have a high caloric value, being the kibbeh the one with the highest caloric value per 100 g, followed by the sfijas and the breaded cutlets. The chosen method to complete the descriptive study was surveys, which determined the sensory properties and the degree of satisfaction and acceptability. They included a group of fifty participants from San Miguel de Tucumán. The results demonstrated that seitan-based products are adequate, have a high degree of acceptability and are delicious with respect to its sensory properties. The aim of this study is to lay the foundations for further research, while promoting the manual preparation of seitan and foods made from this vegetable protein, so as to provide consumers with more information about the wide variety of alternatives to their regular diet.O Seitán é o glúten de trigo e é denominado carne vegetal por seu aspecto similar à mesma. É elaborado mediante o amassamento da farinha de trigo e posterior lavagem, para eliminar o amido. Depois é fervido com alga Kombu e tamari (molho de soja) para enriquecê-lo em vitaminas e minarias e para adquirir cor. Possui um alto conteúdo proteico, baixo em carboidratos e gordura, por ser um originário da China. Os japoneses de orientação macrobiótica introduziram-no nos Estados Unidos, principalmente através dos Mórmons e Adventistas do Sétimo Dia, ao redor de 1940. Depois foi difundido entre aqueles que praticam o vegetarianismo. A pesquisa foi realizada baseada em um tipo de estudo exploratório-descritivo. O estudo exploratório foi realizado através da elaboração artesanal de seitán e sua inclusão em diferentes preparações alimentícias. Os produtos que foram elaborados com sucesso foram: milanesas, sfijas e kipe. Foi realizada a quantificação de macronutrientes e antioxidantes e finalmente, com os resultados obtidos, calculou-se o valor calórico por porção e por 100 g de cada produto elaborado. A quantificação de macronutrientes indica que tanto o seitán como os produtos elaborados possuem um elevado conteúdo proteico e, em relação à valorização nutricional, as três preparações apresentam um alto valor calórico, sendo o kile o de maior calorias para cada 100 g de alimento, seguido das sfijas e, por último, das milanesas. O estudo descritivo foi realizado através de questionários, que determinaram as características organolépticas, o grau de satisfação e a aceitação, nas quais participou um grupo de cinquenta pessoas habitantes da capital do estado de Tucumán. Os resultados evidenciaram que os produtos elaborados com seitán são satisfatórios, possuem um algo grau de aceitação e são agradáveis no que diz respeito às suas características organolépticas. Com este trabalho pretende-se estabelecer as bases para gerar futuras pesquisas e, ao mesmo tempo, promover a elaboração artesanal do seitán e dos alimentos preparados a partir desta proteína vegetal, ampliando o conhecimento da sociedade sobre a grande alternativa disponível na sua dieta habitual.Fil: Gordillo, Maria. Universidad del Norte Santo Tomás de Aquino; Argentina;Fil: Rollan, Graciela Celestina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Centro de Referencia Para Lactobacilos (i); Argentina; Universidad del Norte Santo Tomás de Aquino; Argentina;Fil: Nader, Maria Elena Fatima. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Centro de Referencia Para Lactobacilos (i); Argentina; Universidad del Norte Santo Tomás de Aquino; Argentina

Inactivation of Listeria monocytogenes and Salmonella Typhimurium in strawberry juice enriched with strawberry polyphenols

BACKGROUND: Low molecular-weight phenolic fractions (LMPFs) were extracted from Albion (LMPF-A) and Camarosa (LMPF-C) strawberry cultivars. Their antibacterial activity against Listeria monocytogenes and Salmonella Typhimurium cocktails in vitro and in vivo was investigated using strawberry juice as a food model. This study also sought to determine their antibacterial mechanism. RESULTS: Quercetin was identified as a principal compound in both phenolic fractions. The minimum bactericide concentration (MBC) values were 750 and 850 μg mL−1 (LMPF-C) and 800 and 950 μg mL−1 (LMPF-A) against S.Typhimurium and L. monocytogenes, respectively. The possible antibacterial activity of the phenolic extracts could be related to the release of phosphate and potassium ions, the effect of the disruption of membrane integrity on L. monocytogenes, and the effect of the inhibition of dihydronicotinamide adenine dinucleotide (NADH) oxidase activity on S. Typhimurium. Quercetin and kaempferol were the most active compounds in producing bacterial damage. Strawberry juice supplemented with the phenolic fractions and incubated at 37, 20, and 4 °C reduced bacterial viability; moreover, after treatment with the phenolic fraction at the lowest temperature, no viable cells were detected after 7 days’ incubation. Salmonella was more sensitive to the supplements than Listeria in strawberry juice. CONCLUSIONS: This study could form the basis for the development of natural antibacterial agents that could be included in natural juice or used by the pharmaceutical industry.Fil: Vallejo, Claudia Veronica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentina. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Microbiología "Luis Verna". Cátedra de Microbiología General; ArgentinaFil: Minahk, Carlos Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; ArgentinaFil: Rollan, Graciela Celestina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; ArgentinaFil: Rodriguez Vaquero, Maria Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentina. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Microbiología "Luis Verna". Cátedra de Microbiología General; Argentin

Scindapsus aureus as potential biomarker of polluted environment

Living organisms are subject to different environmental effects, including physical, biological or chemical factors. In front of pollution, which can be defined as an aggression, the organisms must be adapted to survive. In microsomal fraction of cells, there is an oxidase enzymatic complex, whose central element is the cytochrome P450, able to eliminate certain harmful substances. The main action of P450 system is to introduce a functional group to foreign lipophilic compound, which deveins water-soluble and it excretion was facilitated. In this study a method, originally designed to measure P450 activity in animal cells, was modified and adapted for application in plant cells from contaminated environments. Scindapsus aureus also namely Epipremnum aureum, is considered between the best plants with air purification ability. The aim of this work was to study the effect of polluted environments on this plant species, to determining its potential use as contamination biomarker. The results indicated that P450 activity was manifested only in saturated cell-free extract dialysates from those plants exposed to high contamination during periods longer than 30 days. The induction of this enzyme, with detoxificant power, could depend of pollutant type, and/or exposure times. Few studies using plants as air contamination biomarker by CO were conducted. The results obtained allow recommend susceptible species for quantifying indirect pollution in offices, laboratories, factories, where the workers are exposed 8 h daily, during several years.Fil: Cruz, Rosa Magdalena. Universidad Nacional de Tucuman. Facultad de Bioquímica, Química y Farmacia. Instituto de Farmacia. Cátedra de Salud Publica; ArgentinaFil: Fuentes de Curia, Maria Elena. Universidad Nacional de Tucuman. Facultad de Bioquímica, Química y Farmacia. Instituto de Farmacia. Cátedra de Salud Publica; ArgentinaFil: Khouri, Eduardo Alejandro. Universidad Nacional de Tucuman. Facultad de Bioquímica, Química y Farmacia. Instituto de Farmacia. Cátedra de Salud Publica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rollan, Graciela Celestina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; ArgentinaFil: Gonzalez, Silvia Nelina. Universidad Nacional de Tucumán. Instituto de Biotecnología Farmacéutica y Alimentaria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Biotecnología Farmacéutica y Alimentaria; Argentina. Universidad Nacional de Tucuman. Facultad de Bioquímica, Química y Farmacia. Instituto de Farmacia. Cátedra de Salud Publica; Argentin

Fermentación láctica de cereales y granos ancestrales andinos

Los cereales son la fuente de energía dietética más importante en todo el mundo; el trigo, el arroz y el maíz actualmente proporcionan aproximadamente la mitad de la fuente de energía alimentaria de la humanidad. Por otro lado, el aumento de pacientes celíacos en todo el mundo ha motivado el desarrollo de alimentos sin gluten utilizando tipos de harina alternativas al trigo, como arroz, maíz, y pseudocereales (amaranto, quinoa y trigo sarraceno). La importancia de explotar los cereales y pseudocereales para la elaboración de alimentos saludables y nutritivos ha estimulado a los productores de alimentos a desarrollar diferentes estrategias adecuadas para su procesamiento. La fermentación con bacterias lácticas (BAL) es uno de los métodos más antiguos, sencillo y económico para producir, conservar, mejorar propiedades sensoriales, calidad nutricional y funcional de alimentos en general. Esta revisión proporciona una visión general sobre la fermentación de cereales y pseudocereales por BAL destacando la capacidad de estas bacterias para interactuar con los componentes de estos granos durante la elaboración de panificados y pastas.Alimentos fermentados tradicionales preparados a partir de cereales como el maíz, arroz, mijo o el sorgo, son comunes en África. Estos alimentos tienen un gran impacto en la nutrición, la salud y la economía social de los pueblos del continente, a menudo plagados de sequía, hambre y enfermedades. El maíz es económicamente uno de los cultivos más importantes en Latinoamérica y tiene un papel importante en la identidad cultural y social de los pueblos. En este capítulo se describirán algunos alimentos y bebidas fermentadas indígenas tradicionales de África y Latinoamérica, y se detallarán los modos de preparación y la microbiota dominante de la fermentación. Los numerosos efectos beneficiosos de la fermentación láctica de los cereales y pseudocereales pueden explotarse para diseñar alimentos o ingredientes de granos novedosos y más saludables. El suministro de nuevos productos bio-enriquecidos obtenidos por fermentación de estos cultivos representaría un avance significativo para asegurar una adecuada nutrición a la población en general y especialmente a una franja importante de individuos con necesidades diferentes.Fil: Rollan, Graciela Celestina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; Argentin

The peptide hydrolase system of Lactobacillus reuteri

Peptide hydrolase system of Lactobacillus reuteri CRL 1098, a lactic acid bacteria of sourdough origin, was investigated. This microorganism has a broad range of peptidases consisting of an active aminopeptidase, X-Prolyl-dipeptidylaminopeptidase, dipeptidase and tripeptidase. Aminopeptidase, iminopeptidase and endopeptidase are most likely located in the cytoplasmic fraction showing no detectable association with the cell membrane, while dipeptidase and tripeptidase are mainly associated with the latter fraction. The peptidases are metalloenzymes activated by Co2+ and inhibited by Cu2+, Hg2+, Cd2+ and by metal-complexing reagents. The aminopeptidase activity inhibited by EDTA can be restored by Mn2+ while that of di- and tripeptidase treated with 1,10-phenantroline can be restored by Zn2+ and Co2+, respectively.Fil: Rollan, Graciela Celestina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucuman. Centro de Referencia Para Lactobacilos; ArgentinaFil: Font, Graciela Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucuman. Centro de Referencia Para Lactobacilos; Argentin

Functionality of lactic acid bacteria peptidase activities in the hydrolysis of gliadin-like fragments

Aims: To evaluate the role of the peptidase activities from sourdough lactic acid bacteria (LAB) in the degradation of α-gliadin fragments. Methods and Results: Different proline-containing substrates were hydrolysed by LAB indicating pro-specific peptidase activities. Lactobacillus plantarum CRL 775 and Pediococcus pentosaceus CRL 792 displayed the highest tri- and di-peptidase activities, respectively. Lactobacillus plantarum strains hydrolysed more than 60%α-gliadin fragments corresponding to the 31-43 and 62-75 amino acids in the protein after 2 h. None of the LAB strains alone could hydrolyse 57-89 α-gliadin peptide; however, the combination of L. plantarum CRL 775 and P. pentosaceus CRL 792 led to hydrolysis (57%) of this peptide in 8 h. Conclusions: The capacity of LAB strains to degrade α-gliadin fragments was not correlated to individual peptidase activities. Several strains separately degraded the 31-43 and 62-75 α-gliadin fragments, while the 57-89 peptide degradation was associated with the combination of peptidase profiles from pooled LAB strains. This is the first report on the peptide hydrolase system of sourdough pediococci and its ability to reduce α-gliadin fragments. Significance and Impact of the Study: This study contributes to a better knowledge of sourdough LAB proteolytic system and its role in the degradation of proline-rich α-gliadin peptides involved in celiac disease. © 2008 The Authors.Fil: Gerez, Carla Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; ArgentinaFil: Font, Graciela Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; Argentina. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; ArgentinaFil: Rollan, Graciela Celestina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; Argentin

Gluten breakdown by lactobacilli and pediococci strains isolated from sourdough

Aims: To evaluate the growth and metabolic activity of lactobacilli and pediococci strains in a gluten base medium (GBM), formulated for a proper selection of proteolytic strains to be used in sourdough fermentation. Methods and Results: Proteolytic activity by lactic acid bacteria (LAB) was evaluated by SDS-PAGE and by the amino acids released determined by reversed-phase high-performance liquid chromatography. Only 13 LAB (nine lactobacilli and four pediococci), among the 42 evaluated were able to utilize gluten as nitrogen source and to grow in GBM. Pediococcus pentosaceus CRL 797 showed a similar proteolytic activity to lactobacilli strains. In the majority of the cultures, basic amino acid group increased (c. 80% after 12 h incubation) mainly due to the release of ornithine, a flavour precursor of bread. Lysine, a limiting essential amino acid in wheat flour, increased by 150% in cultures of P. pentosaceus CRL 797. Conclusions: This study allows selecting P. pentosaceus CRL 797 and L. plantarum CRL 759 as potential starter culture for type III sourdough fermentation. It is shown for the first time that pediococci strains isolated from sourdough are proteolytically active on gluten. Significance and Impact of the Study: The physiological studies on gluten breakdown by LAB will contribute to the better selection of strains to produce breads with enhanced organoleptic characteristics.Fil: Gerez, Carla Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; ArgentinaFil: Rollan, Graciela Celestina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; ArgentinaFil: Font, Graciela Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; Argentina. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; Argentin

Antifungal activity of Lactobacillus fermentum CRL 251

Spoilage of food is mainly due to fungal growth. In addition to the great economic losses derived from the presence of mould, another concern is the potential mycotoxin production that may cause public health problems. In recent years, bio-preservation [the use of microorganisms and/or their metabolites to prevent spoilage and to extend the shelf life of foods] has gained increasing interest due to consumers? demands. Lactic acid bacteria (LAB) as bio-preservation organisms are of particular interest: they have been used for centuries as starter cultures in the food industry and are able to produce different kind of bioactive molecules, such as organic acids, peptides, fatty acids, hydrogen peroxide and bacteriocins. The present study was undertaken to evaluate the potentiality of Lactobacillus fermentum CRL 251 to inhibit mould and yeasts growth and characterize the metabolite/s involved. L. fermentumCRL 251 was grown in MRS broth (pH 6.5) at 37ºC for 24 h. The cell-free supernatants (CFS) was sterilized by filtration and used in the antifungal assays. The antifungal activity on various species of molds and yeasts was performed using the Microtitre Plate Well Assay. Conidial germination or yeast growth was determined during 48 h at 30ºC by measuring the optical density (OD580nm). The activity of CFS was determined in both neutral (pH 7, CFSn) and acidic (pH 3.8, CFSa) conditions. The activity of CFSn at different conditions of temperature (50, 100, 121ºC), pH range (3.0-8.0), and water activity (aw 0.995-0.901) was also determined. In addition, the effect of agitation on the antifungal compound/s production was evaluated. The resultsdemonstrated thatL.fermentum CRL 251 has inhibitory effect against a broad range of filamentous fungi (molds) and, to a greater extent, against spoilage yeasts in both, neutral and acidic conditions. The production of the antifungal compoundsstarts during the exponential phase and reaches the maximum value in the stationary phase where the activity (70-80 % inhibition)remained constant.The LAB growth under agitation condition not showedsignificant effect (p≤0.05) on the antifungal compounds production.The activity was stable during heat treatment and it remained constant even after autoclaving (121°C for 15 min). Maximum activity was determined at pH values between 3.0 and 5.0; at higher pH values no activity was observed. The inhibitory activity was stable at aw values between 0.995-0.937. No inhibitory activity was detected at awlower than 0.937. The antifungal peptides were partially purified and the molecular mass was estimated (approximately ≤ 10 kDa). This is the first report on a proteinaceous antifungal compound(s) productionby L. fermentum.Fil: Gerez, Carla Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; ArgentinaFil: Conci, Julieta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; ArgentinaFil: Rollan, Graciela Celestina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; ArgentinaV International Symposium on Lactic Acid Bacteria: Benefiting from Lactic Acid Bacteria. Progress in Health and FoodSan Miguel deTucumánArgentinaConsejo Nacional de Investigaciones Científicas y Técnicas. Centro de Referencia para Lactobacilo

Effect of galactose and glucose on the exopolysaccharide production and the activities of biosynthetic enzymes in Lactobacillus casei CRL 87

Aims: The objective of this work was to study the influence of the sugar source on exopolysaccharide (EPS) production and the activities of the enzymes involved in the synthesis of sugar nucleotides in Lactobacillus casei CRL 87. The relationship between these enzymes and EPS formation was determined. Methods and Results: The concentration of EPS was estimated by the phenol/sulphuric acid method while the chemical composition of purified EPS was investigated using gas-liquid chromatography. Biosynthetic enzyme activities were determined spectrophotometrically by measuring the formation or disappearance of NAD(P)H at 340 nm. Polysaccharide production by Lb. casei CRL 87 was 1.7 times greater on galactose than on glucose. The isolated polymer was composed of rhamnose, glucose and galactose. The activities of uridine-diphosphate (UDP)-glucose-pyrophosphorylase, thymidine-diphosphate (dTDP)-glucose-pyrophosphorylase and the dTDP-rhamnose-synthetic enzyme system were higher in galactose-grown than in glucose-grown cells. When an EPS- mutant strain was used, galactokinase activity was not detected on galactose, this sugar not being available for the formation of sugar nucleotides for further EPS production, dTDP-glucose-pyrophosphorylase and dTDP-rhamnose-synthetic enzyme system activities were lower than the values found for the wild type strain. Conclusions: The carbon source present in the culture medium affects EPS production by Lb. casei CRL 87. The greater polymer synthesis by galactose-grown cells is correlated with the higher UDP-glucose-pyrophosphorylase, dTDP-glucose-pyrophosphorylase and dTDP-rhamnose-synthetic enzyme system activities. Initial sugar metabolism is also an important step for the synthesis of EPS precursors by this strain. Significance and Impact of the Study: Knowledge of the effect of the sugar source on EPS production and the activities of biosynthetic enzymes provides information about the mechanisms of regulation of the synthesis of EPS which can contribute to improving polymer production.Fil: Mozzi, Fernanda Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucuman. Centro de Referencia Para Lactobacilos; ArgentinaFil: Rollan, Graciela Celestina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucuman. Centro de Referencia Para Lactobacilos; ArgentinaFil: Savoy, Graciela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucuman. Centro de Referencia Para Lactobacilos; ArgentinaFil: Font, Graciela Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucuman. Centro de Referencia Para Lactobacilos; Argentin