Optimization of growth conditions for the isolation of dextran producing leuconostoc spp. from indigenous food sources

Leuconostoc are known to produce dextran, which have great commercial importance in chemical, medical and food industry. The present study is an attempt to select the best medium for the isolation of indigenous dextran producing Leuconostoc, measuring their enzyme activities for dextransucrase, production of dextran and identification of dextran producing Leuconostoc CMG706, CMG707, CMG710 and CMG713. Since, dextran producing Leuconostoc produce slimy colonies, twenty-four slime producing bacterial strains were isolated from different food sources, fruits and vegetables. Three different isolation medium were evaluated for the isolation of Leuconostoc only and the best one was found to be one containing sucrose and sodium azide. Further, all slime producing bacterial strains were screened for enzyme activity of dextransucrase, which is responsible for dextran production. Four bacterial strains CMG706, CMG707, CMG710 and CMG713 giving high enzyme activities were selected for dextran production and identified

Functional change of dextran-modified alpha-amylase from bacillus acidocaldarius

ALPHA-AMYLASE from Bacillus acidocaldarius was modified by covalent coupling to activated dextran with retained activity of 77.7%. After conjugation, the enzyme was stable within a broader pH range than the native enzyme and its optimum temperature increased by 10°C compared to the native enzyme. The conjugated a amylase exhibited a higher K[m] [Michaelis constant], lower V[max] [maximal reaction rate] and lower E[A] [activation energy] than the native enzyme. Covalent attachment of alpha- amylase to activated dextran protected the enzyme against heat inactivation. In the presence of the substrate, the conjugated enzyme retained 68.2% of its original activity after incubation at 70°C for 30 min which was more than that retained by the native enzyme [50.3%] under the same conditions. The calculated t[1/2] [half-life time] values of heat inactivation energy at 50, 60°C were 89 and 56 mm, respectively for the conjugated enzyme, whereas at these temperatures the native enzyme was less stable [t[1/2] 60 and 47 min, respectively]. The deactivation rate constant at 80°C for the conjugated a-amylase is about 11.9x10[-3]/ min, which is lower than that of the native enzyme [14.8x10[-3]/ min]. Conjugated a-amylase was more stable against chemical denaturation than the native enzyme, and retained 70.6% of its activity in presence of CuSO[4] [10 mM] while the native form of retained only 34.1%

Disociación eléctrica de complejos albúmina-dextran azul: un método para obtener albúmina pura / Electric dissociation of blue dextran-albumin complexes: a method to obtain pure albumin

La disociación eléctrica puede ser un método no lesivo útil para recuperar el componente de interés de complejos formados por componentes de mutua afinidad. Las condiciones usadas generalmente para disociar componentes en cromatografía de afinidad en fase sólida (pH ácido, incremento importante de fuerza iónica, agentes caotizantes, etcétera), son por naturaleza algo drásticos, lo que origina materiales que contienen elementos desnaturalizados parcial o totalmente. En el presente trabajo dosociamos eléctricamente un complejo albúmina dextrán azul (blue dextrán 2000), en un sistema en fase líquida. La albúmina, principal proteína sérica que muestra gran afinidad por diversos colorantes, fue obtenida con el 100 % de puerza. Materiales con tal grado de pureza como por ejemplo, para ser marcados con isótopos o flurocromos y usarlos como antígenos para obtener antisueros o materiales biológicos de referencia. El proceder de disociación eléctrica utilizado, puede ser susceptible de utilización en sistemas de cromatografíaa de afinidad en fase sólida