Crecimiento y formación de polisacáridos de cepas de Sinorhizobium meliloti en un fermentador tipo air-lift: influencia en la velocidad de nodulación en plantas de alfalfa / Crowth of Sinorhizobium meliloti strains and exopolysaccharide formation in an air-lift fermentor: influence on the nodulation rate in alfalfa plants

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.

Producción de renina por Rhizomucor miehei NRRL 3169 / [Rennet production by Rhizomucor miehei NRRL 3169]

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.

Producción de pectinasas a partir de Penicillium simplicissimum A3263 en un medio con harina de semilla de amaranto / [Production of pectinases by Penicillium simplicissimum A3263 in an amaranth-seed flour medium]

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.

Obtención de xantano a partir de Xanthomonas campestris B-1459 en fermentadores con agitación mecánica / [Isolation of xanthan from Xanthomonas campesteris B-1459 in mechanically agitated fermentors]

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.

Producción de xantano a partir de Xanthomonas campestris B-1459 / [Xanthan production by Xanthomonas campestris B-1459]

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.