Liquid-liquid extraction of commercial and biosynthesized nisin by aqueous two-phase micellar systems.

Nisin is a natural additive for conservation of food, and can also be used as a therapeutic agent. Nisin inhibits the outgrowth of spores, the growth of a variety of Gram-positive and Gram-negative bacteria. In this paper we present a potentially scalable and cost-effective way to purify commercial and biosynthesized in bioreactor nisin, including simultaneously removal of impurities and contaminants, increasing nisin activity. Aqueous two-phase micellar systems (ATPMS) are considered promising for bioseparation and purification purposes. Triton X-114 was chosen as the as phase-forming surfactant because it is relatively mild to proteins and it also forms two coexisting phases within a convenient temperature range. Nisin activity was determined by the agar diffusion assay utilizing Lactobacillus sake as a sensitive indicator microorganism. Results indicated that nisin partitions preferentially to the micelle rich-phase, despite the surfactant concentration tested, and its antimicrobial activity increases. The successful implementation of this peptide partitioning, from a suspension containing other compounds, represents an important step towards developing a separation method for nisin, and more generally, for other biomolecules of interest.

Thermal characteristics of recombinant green fluorescent protein (GFPuv) extracted from Escherichia coli.

AIMS: The thermal stability of isolated and extracted recombinant green fluorescent protein (GFPuv) was evaluated by analysing the loss of fluorescence intensity. METHODS AND RESULTS: GFPuv was expressed by Escherichia coli, extracted by the three-phase partitioning method and purified by elution through an hydrophobic interaction column. The collected fractions were further diluted in Tris-HCl-EDTA (pH 8.0) and subjected to continuous heating at set temperatures (45-95 degrees C). From a standard curve relating fluorescence intensity to GFPuv concentration, the loss of fluorescence intensity was converted to denatured GFPuv concentration (microg ml-1). To determine the extent of the thermal stability of GFPuv, decimal reduction times (D-values), z-value and energy of activation (Ea) were calculated. CONCLUSIONS: For temperatures between 45 and 70 degrees C, extracted native GFPuv activity decreased from 11 to 75% relative to initial native protein concentration above 70 degrees C, the average decrease in GFPuv fluorescence was between 72 to 83%. SIGNIFICANCE AND IMPACT OF THE STUDY: The thermal stability of GFPuv provides the basis for its potential utility as a fluorescent biological indicator to assess the efficacy of the treatment of liquids and materials exposed to steam.

Efeito do valor de pH do meio na estabilidade da peroxidase e de carotenos de cenoura (Daucus carota L.). / Effect of pH on stability of peroxidase and of carotenes in carrot (Daucus carota L.)

Estudou-se a influencia do valor de pH do meio na atividade enzimatica da peroxidase e na estabilidade de beta-caroteno de cenoura fresca. Os valores de pH estudados foram de 4,0; 5,0; 6,0; 6,2; 6,4; 6,6; 6,8; 7,0 e 8,0.A atividade enzimatica maxima foi verificada na faixa de pH compreendida entre 6,0 e 6,4.O teor de beta-caroteno manteve-se inalterado para todos os valores de pH ensaiados