Résumé
En este trabajo, se estudió la influencia de los polisacáridos formados por cepas de Sinorhizobium meliloti sobre la velocidad de nodulación en plantas de alfalfa. Las experiencias fueron realizadas en agitador rotatorio y en un fermentador con circulación de líquido por inyección de aire, empleando diferentes cepas de S. meliloti, El crecimiento bacteriano fue determinado por recuento de células viables y la concentración del exopolisacárido por precipitación con etanol. Se alcanzaron concentraciones máximas del orden de 1.10 (10) células viables/ml y de 11 g/l de polisacárido. Los estudios de crecimiento de plantas de alfalfa en cámara climatizada mostraron que se producía una reducción en el tiempo de aparición de nódulos de 10 a 4 días, cuando las mismas eran inoculadas con suspensiones diluidas 1/10, manteniendo las cepas sus propiedades simbióticas.
Sujets)
Argentine , Polyosides bactériens , Sinorhizobium melilotiRésumé
The production of rennet was studied, using different strains of the fungus Rhizomucor miehei. The selection and preservation of strains, type of growth, media design and operation conditions were evaluated. The experiments were carried out in Erlenmeyer flasks in rotary shaker at 250 rpm and 2.5 eccentricity, and in mechanically stirred fermentors of the New Brunswick type, at 30 degrees C. In the studies concerning strain selection, the best strain was Rhizomucor miehei NRRL 3169. The major titles of enzyme were obtained in batch process at 168 h, with 884 SU/ml, whereas in mechanically stirred fermentors the best value was 1160 SU/ml. These values were far more superior to former ones published by various experts.
Résumé
The present work studies the production of pectinases using a strain of Penicillium simplicissimum A3263 and considering the influence of adding Amaranthus cruentus seed meal in a selected medium. We also considered the influence of aeration on enzyme production. Research was oriented towards the production of pectin lyase, the enzyme having the highest commercial value. This work was carried out in Erlenmeyer flasks in rotary shaker to select the medium and in a mechanically stirred fermentor to study aeration. The microorganism was developed as pellets of 1 mm diameter. Enzyme levels were of the order of 8216.21 pectin lyase units and 167.57 polygalacturonase units per gram of fungal biomass, respectively, using a medium containing 40 g/l of amaranth seed meal. As for the influence of aeration, it was determined that the higher values were obtained at 750 rpm corresponding to an oxygen absorption rate of 2691 ml O2/lh for an air flow of 1 l/l.min. The results obtained are considered very important in view of the fact that they exceeded in 550
those obtained by other authors.
Résumé
In this paper the influence of the amaranth seed meal and the aeration conditions on the alpha-amylase production by Aspergillus niger NRRL 3112 were studied. The assays of selection of culture medium were carried out in a rotary shaker at 250 rpm and 2.5 cm stroke. The aeration conditions were studied in a mechanically stirred fermentor New Brunswick type. A concentration of alpha-amylase of 2750 U.Dun/ml was achieved at 120 h with a dry weight of 8.0 g/l, using a base medium with 5.0 g/l Amaranthus cruentus seed meal. In the experiment performed in a New Brunswick fermentor, the highest value was 2806 U.Dun/ml. This result was obtained after 120 h, operating at 300 rpm and an airflow of 1 l/l. min. in a limited dissolved oxygen concentration. It was determined that the increase in the agitation rate was not favorable to the enzyme production, despite that an increase was verified in the dissolved oxygen. The morphology of the microorganism, in long and ramified hyphae, was the critical factor to obtain higher levels of alpha-amylase.
Sujets)
alpha-Amylases , Colorant amarante , Aspergillus niger , Agents colorants , Milieux de culture , Indicateurs et réactifs , Protéines fongiques/biosynthèse , Aspergillus niger , FermentationRésumé
Xanthan production from Xanthomonas campestris was studied by a mechanically shaken fermentor. Influence of glucose concentration, aeration of culture media, rheology of broths and pH control was evaluated. Different aeration conditions based on variation of stirring rates were assayed. Substrate concentration was determined according to the Miller method, and polymer production was performed by the Cadmus method. The higher xanthan levels (i.e. 2.3
) were obtained at 750 rpm, with 1 v/v. min. In such conditions, viscosity ranges about 7000 cPoise and a low level of dissolved oxygen were detected in the culture medium. Xanthan production was influenced by the glucose concentration and the presence of amaranth within the culture medium. In the processes wherein an automatic control of pH was performed, the polymer concentration did not increase regarding to processes involving regular pH evolution.
Résumé
The production of xantano from Xanthomonas campestris B-1459 was analyzed. The experiments were performed in shaked flasks at 250 rpm and 2.5 cm eccentricity. Using a base modified medium it was possible to achieve xantano concentration of 35 g/l in 72 h of process. The modified medium contained glucose as carbon source, and yeast extract, meat peptone, malt extract and amaranth meal as growth factors and nitrogen sources, in a KH2PO4/K2HPO4 buffer.
Résumé
The growth of Bradyrhizobium japonicum E-109 using cheese whey as carbon source was studied. The cheese whey was previously hydrolyzed by acid or enzymatic treatment with purified beta galactosidase or a crude extract from Kluyveromyces fragilis. The results obtained demonstrated that the use of the modified enzymatic hydrolyzed whey as carbon source allowed the growth of B. japonicum E-109 reaching a concentration of approximately 10(10) viable cells/ml. These results are considered of industrial value because the poluent power whey is greatly reduced.
Résumé
Se estudio la produccion de glucosa-isomerasa utilizando una cepa de Streptomyces phaeochromogenes NRRL B-3559. Se considero la influencia de la composicion del medio cultivo y de las condiciones de aeracion.De tres tipos de colonias bien diferenciadas que el microorganismo es capaz de desarrollar, las grises fueron de la mayor produccion enzimatica. Con el objeto de evitar la variabilidad de la poblacion microbiana y obtener resultados sobre la composicion del medio, se vio que la concentracion de cobalto es critica en cuanto a los niveles de enzima alcanzados.Empleando una concentracion de Cl2Co.6H2 de 0,18 g/l se obtuvieron 1600 UE/l. Los estudios de aeracion realizados en fermentadores con agitacion mecanica del tipo convencional, mostraron que es posible obtener valores de actividad enzimatica similares a los producidos en erlenmeyers agitados, operando a 550 rpm y un flujo de aire de 1 1/1.min. Se demostro que el cultivo estaba adecuadamente aerado en razon de que los valores de consumo y demanda celular de oxigeno fueron semilares
Sujets)
Carbohydrate epimerases , Streptomyces , Milieux de cultureRésumé
Se estudio la influencia de mutantes respiratorias de una Saccharomyces fragilis en la produccion de biomasa. Se considero el efecto de distintas proporciones de una mutante con capacidad respiratoria nula en poblaciones de celulas de levadura en relacion al rendimiento celular. Los resultados obtenidos en estas esperiencias muestran que para procesos donde se utiliza el 100% de celulas normales (RC) es posible obtener 5,6 g/l de masa celular mientras que operando con el 100% de mutantes respiratorias (RD) solo se alcanza una concentracion de 1,6 g/l para iguales condiciones de cultivo. Estos estudios muestran la importancia del conocimiento de la distribucion de la poblacion de celulas, ya que el rendimiento en biomasa esta directamente relacionado a su composicion