Response surface methodology for the optimization of keratinase production in culture medium containing feathers produced by Kocuria rosea.

A 43-fold increase in keratinase production by Kocuria rosea was achieved in batch fermentation using response surface methodology. Factorial designs were used to select the components of a culture medium that showed a significant effect on keratinase production. An orthogonal-central composite experimental design was performed, with only two (feathers and magnesium) from nine initial compounds being further analyzed by response surface methodology. An optimum keratinase production of 14 886.9 U/mg was obtained with the following medium composition (per litre): NH4Cl, 0.3 g; NaCl, 0.3 g; K2HPO4, 3.2 g; KH2PO4, 4.0 g; MgSO4.6H2O, 0.5 g; yeast extract, 0.1 g; and finely milled feathers, 30 g. The medium was shaken at 400 r/min with an incubation period of 14 h at 40 degrees C.

A biotechnological process for treatment and recycling poultry feathers as a feed ingredient.

A strain of Kocuria rosea with keratinolytic capacity was cultured aerobically on submerged feathers to obtain a fermented feather meal (FFM). This FFM enriched with cells of K. rosea mainly contains crude protein (71%). The pepsin digestibility of the fermented product (88%) was similar to the value of the commercial feather meal and more than 70% greater that untreated feathers. The bacterial biomass improved the content of amino acids lysine (3.46%), histidine (0.94%) and methionine (0.69%). Additionally, the amino acid availability tested by in vivo assay was greater than commercial feather meal. The microbial cells also supplied carotenoid pigments to FFM (68 ppm). These results suggest that feather meal enriched with K. rosea may be useful in animal feeding as protein and pigment source.

Effect of gluconic acid as a secondary carbon source on non-growing L-lysine producers cells of Corynebacterium glutamicum. Purification and properties of 6-phosphogluconate dehydrogenase.

We studied the production of L-lysine in Corynebacterium glutamicum ATCC 21543 non growing cells obtained by nutrient limitation. Statistical analysis revealed significant differences in the L-lysine titers of glucose, gluconic acid or glucose-gluconic acid cultures. Higher L-lysine titer obtained in batch cultures with mixed carbon sources or gluconic acid alone were found to be associated with a high 6-phosphogluconate dehydrogenase activity (6PGDH, E.C.1.1.1.44). This enzyme is a pivotal enzyme within the hexose monophosphate pathway, and thus of importance for L-lysine production. 6PGDH was purified and characterized. The purified enzyme migrates as a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with a molecular mass of 52.5 kDa. The molecular mass of the native enzyme was estimated to be 120 kDa by molecular exclusion chromatography, thus suggesting a homodimeric structure. The amino terminal sequence shows a strong similarity (a match of 86% of the first 20 amino acid) to the 6PGDH from other microorganisms such as, E. coli and B. subtilis. The pI of the dimeric native enzyme and the optimum pH were 6.2 and 8.0, respectively. For the oxidative decarboxylation of 6-phosphogluconate, K(m) of 71 &mgr;M and 43 &mgr;M were obtained for 6-phosphogluconate and NADP(+), respectively.

[L-lysine production by Corynebacterium glutamicum non growing cells]. / Producción de L-lisina por células en no crecimiento de Corynebacterium glutamicum.

The production of L-lysine by Corynebacterium glutamicum (GIGO) non growing cells was studied. A system of fermentation was developed where it was possible to separate the physiologic states of growth from those of production of L-lysine. The biomass propagation step carried out in batch cultures with yeast extract and glucose substrate showed cellular growth without production of L-lysine. The production of L-lysine was achieved when the cells were collected and incubated in the mineral glucose medium without yeast extract. In this condition non cellular growth was observed and the yield product (YP/S) and the specific production of L-lysine were increased (3 times) in rapport with the values obtained with the conventional fermentation system with overlapping of cellular growth and production of L-lysine. The oxygen limitation led to the synthesis of lactic acid and acetic acid as alternative byproducts, which diminished when improving the oxygenation conditions by increasing the agitation rate of the cultures.

Síndrome de Cushing / Syndrome of Cushing

Describe un caso de Síndrome de Cushing diagnóstico que se dió como primera posibilidad por las manifestaciones clínicas presentadas incialmente. La evolucióon fue satisfactoria posterior a la administración de ketoconazol. La resonancia magnética nuclear reveló un adenoma pituitario...

The metabolism of gluconate in Escherichia coli: a study in continuous culture.

The gluconate metabolism in Escherichia coli involves duplicate activities of transport and phosphorylation for gluconate. In both cases, these activities can be differentiated in vitro by their different affinities for the substrate. In addition, the two gluconokinases can be differentiated by their heat sensitivities. The technique of continuous culture was used to investigate the influence of the growth rate on this metabolism in an E. coli HfrG6 strain during gluconate-limited growth under conditions of high and low oxygen concentrations. The transport and phosphorylation for gluconate, induced when the cells are cultivated in media with gluconate were differently influenced by the culture dilution rate. These activities were induced under the two conditions investigated; however, the low affinity transport system for gluconate and the thermosensitive gluconokinase were not detected under conditions of high and low oxygen concentrations, respectively. The induction of the dehydratase was favoured under conditions of low oxygen concentration. The experimental data suggest that induction and repression work together to regulate the levels of these activities during gluconate-limited growth conditions. Furthermore, that an effector molecule distinct from gluconate might be involved in the induction of the dehydratase.

Aislamiento y purificacion de amastigotes de Leishmania braziliensis: su aplicacion al estudio comparativo de la superficie cecular de amastigotes y promastigotes de la cepa NR. / Isolation and purification of Leishmania braziliensis amastigotoes: its use in the comparative study of cellular surface of amastigotes and promastigotes of the NR strain

Se desciben dos metodos rapidos y sencillos para el aislamiento y purificacion, con alto rendimiento, de amastigotes de Leishmania braziliensis a partir de lesiones cutaneas (granulomas) de hamster, los mismos se basan en homogenizacion controlada del tejido, centrifugacion diferencial y purificacion final en gradientes discontinuos de sacarosa (metodo A) o gradientes continuos autoformativos de Percoll (metodo B). Los amastigotes aislados son practicamente puros (> igual 99%), 90, 95% viables, altamente infectivos para el hamster y capaces de diferenicarse in vitro a promastigotes proliferativos a 28o.C El rendimiento alcanza valores entre 0,1 y 10 elevado a 9 amastigotes por gramo de tejido procesado. Las propiedades superficiales de promastigotes de cultivo y amastigotes aislados por el metodo A descrito arriba fueron comparadas usando como criterio la aglutinacion inducida por las lectinas concanavalina A y aglutinina de Ricino. Aunque la aglutinacion inducida por la aglutinina de Ricino es similar en ambas formas del parasito, hay una marcada diferencia en la aglutinabilidad por conacavalina A, la cual es muy alta en la forma promastigote y practicamente inexistente en el amastigote, a concentraciones < igual 50 ug/ml. Los resultados sugieren importantes diferencias en la composicion superficial de las dos formas del organismo, que podrian relacionarse con las diferencias en la infectividad y capacidad de supervivencia en el hospedero de las mismas