Factors influencing protease production by two Antarctic strains of Stenotrophomonas maltophilia

The influence of culture medium buffer capacity, the supplementation of culture medium with L-ala and the requirement of calcium for exoprotease production by Antarctic psychrotrophic Stenotrophomonas maltophilia strains ANT-1-1 and ANT-7-1 were examined. When increasing concentrations of calcium chloride (0 to 0.3 g l-1) were added to culture media, maximum protease production yields increased 70-75 (ANT-1-1) and 50 (ANT-7-1), while biomass levels showed little difference. Calcium was also necessary for optimal activity of proteases. L-ala had no effect on protease production. The reduction in buffer capacity, with the consequent change in external pH, had a positive effect, enhancing protease yields. Secretion of proteases into the medium started at the beginning of the stationary phase, corresponding with a rise in pH values up to pH 8.7 and was maximal at 36 h of culture. These results indicate that the regulation of calcium concentration and buffer capacity and also pH monitoring are factors to be considered when the design of an industrial culture medium and the optimisation of protease production processes using these Antarctic strains are concerned.

Selección de cepas bacterianas para la producción de treonina / [Selection of bacterial strains for the production of threonine]

The production of L-threonine in submerged culture was studied in the following bacterial strains; Brevibacterium flavum ATCC 21269, Corynebacterium acetoacidophilum ATCC 21270, Escherichia coli ATCC 21149, E. coli NRRL 12098, E. coli NRRL 12099 and E. coli NRRL 12100. Erlenmeyer flasks with different volumetric relations liquid/recipient, were used to study the influence of the volumetric oxygen transfer rate. B. flavum reached levels of threonine of 0.72 g/l at 96 hours of culture with a volumetric relation liquid/recipient of 1:5. With a relation 1:25 the maximal level was reached at 48 hours (0.60 g/l of threonine) (Table 1). In addition to threonine this strain accumulated in the culture media glutamic acid (+/- 2 g/l), alanine or glycine and proline. With E. coli ATCC 21149 the aeration favored the production of threonine reaching levels of 0.38 g/l in six day cultures with valine and alanine at levels approximate to 2 g/l. Excepting C. acetoacidophilum, all the strains produced threonine at levels of 0.30 to 3.55 g/l (Table 5). E. coli NRRL 12098 and E. coli NRRL 12100 produced only threonine, the culture medium being free from other aminoacids. With E. coli NRRL 12098 levels of 2 g/l were attained but the production was restricted to the presence of yeast extract in the media (Table 2). E. coli NRRL 12100 was the best strain and the inoculum media influenced the production (Table 3) and the best threonine levels were reached in the best aeration conditions assayed (Table 4) with 3.55 g/l for volumetric relations 1:10 and 1.25 g/l for 1:5.

Produccion de enzimas coagulantes de leche por cultivo sumergido aireado de una cepa de Mucor mucedo. / Milk clotting enzymes production by aerated submerged culture of a strain of Mucor mucedo

Mucor mucedo produce enzimas coagulantes de leche al desarrollar en substrato solido (afrecho humedecido) o en cultivo sumergido, aireado. En esta ultima condicion de cultivo, el empleo de caseina o suero de leche como unica fuente nitrogenada permitio detectar actividad coagulante, alcanzandose los mejores niveles de produccion para concentraciones de caseina entre 0,5 y 0,7%. La adicion de glucosa mejoro los rendimientos, considerandose optima una concentracion del 1%, con un aumento del 113% en la produccion. El efecto de los cationes Fe++, Cu++, Mn++ y Zn++ fue variable; su ausencia simultanea deprimio la produccion en un 40%, mientras que su efecto individual era muy ligero o nulo. Los aniones sulfato y fosfato presentaron efectos variables, dependiendo de su concentracion; sus niveles optimos fueron 2x10(-4) M y 2,2x10(-2) M, respectivamente. De los inoculos ensayados se selecciono el constituido por micelio vegetativo desagregado de 72 horas, al 17% (v/v), esto en razon de que se adelanto el pico de produccion y se elevaron y mantuvieron por periodos mas prolongados, los niveles de actividad coagulante. En condiciones optimas se logro como produccion maxima 190 U/ml de caldo

Producción de biomasa y depuración biológica de vinaza de destilería en un proceso de dos etapas / [Biomass production and biological purification of distillation slops in a 2-step process]

In order to lower the chemical demand (COD) of slops from cane molasses alcohol a treatment of two steps which allows the production of single cell protein of Candida utilis and Paecilomyces variotii has been performed. Its use reduces the treatment cost. In the first step the slops without sterilization supplemented with ammonium sulphate (5 g.l-1) and dipotassium phosphate (0.5 g.l-1) was inoculated with C. utilis and P. variotii. The yield was 24 and 18 g.l-1 of dry biomass and COD reduction of 36 and 75

respectively. In the second step, the remainder effluents were treated with Aspergillus niger. The final COD reduction attained was 93 and 92

Produccion y propiedades de la enzima coagulante de leche. / Produccion and properties of milk-clotting enzyme

Se obtuvieron enzimas coagulantes de leche en cultivo en sustrato solido con una cepa de Mucor varians Pispek, previamente seleccionada. El afrecho de trigo humedecido (120% de agua sobre base seca) demostro ser un buen medio de produccion, alcanzando niveles de 4.000 U de actividad coagulante de leche por g de afrecho. La enzima fue extraida de los cultivos con agua y precipitada con sulfato de amonio o con solventes como etanol, metanol o acetona.La enzima cruda es una proteasa acida con actividad optima a pH 3,0. Como la quimiosina de ternero, esta enzima cruda de M.varians pierde actividad con el tratamiento termico. El nivel de actividad lipolitica de la enzima cruda es similar al de algunas preparaciones comerciales y no se demostro actividad antibiotica, ni amilolitica en los extractos crudos

Produccion de un concentrado de proteasa acida de Mucor bacilliformis. / Production of an acid protease concentrate from Mucor bacilliformis

Se obtuvo un concentrado de enzimas congulantes de leche por cultivo de Mucor bacilliformis en afrecho de trigo humectado a 120% de agua sobre base seca con solucion de HC1 0,2 N. El afrecho esterilizado fue dispuesto en bandejas, e inoculado con 5.10 (6) esporos/gr de afrecho seco. Luego de 10 dias de incubacion se extrajo el afrecho enmohecido con agua, se ajusto el pH a 4,4 y se precipito el sobrenadante limpido con etanol. El precipitado fue disuelto en agua clorhidrica (pH 4,5) y concentrado por dialisis contra polietilenglicol 20000. La solucion con una actividad especifica de 1128 U/mg, se utilizo en dos ensayos de elaboracion de queso tipo cremoso