RESUMEN
Extracellular tannase and gallic acid were produced optimally under submerged fermentation at 37 0C, 72 h, pH 5.0, 10 percent(v/v) inoculum and 4 percent(w/v) of the agroresidue pomegranate rind (PR) powder by an Aspergillus niger isolate. Tannic acid (1 percent) stimulated the enzyme production by 245.9 percent while with 0.5 percent glucose, increase was marginal. Tannase production was inhibited by gallic acid and nitrogen sources such as NH4NO3, NH4Cl, KNO3, asparatic acid, urea and EDTA. The partially purified enzyme showed temperature and pH optima of 35 0C and 6.2 respectively which shifted to 40 0C and 5.8 on immobilization in alginate beads. Activity of the enzyme was inhibited by Zn+2, Ca+, Mn+2, Mg+2, Ba+2and Ag+. The immobilized enzyme removed 68.8 percent tannin from juice of aonla/myrobalan (Phyllanthus emblica), a tropical fruit, rich in vitamin C and other essential nutrients. The enzymatic treatment of the juice with minimum reduction in vitamin C is encouraging as non enzymatic treatments of myrobalan juice results in vitamin C removal.
Asunto(s)
Ácido Gálico/análisis , Ácido Gálico/aislamiento & purificación , Aspergillus niger/enzimología , Aspergillus niger/aislamiento & purificación , Enzimas Inmovilizadas/análisis , Enzimas Inmovilizadas/aislamiento & purificación , Fermentación , Lythraceae/enzimología , Tanacetum parthenium/crecimiento & desarrollo , Tanacetum parthenium/enzimología , Activación Enzimática , Frutas , MétodosRESUMEN
1. Trehalase was partially purified from Escherichia coli and characterized. The Km for trehalose was 0.78 mM, the pH optimum 5.5 and the temperature optimum 30 degrees C. 2. Trehalase represented approximately 50 per cent of the total protein released by osmotic shock. The preparation was free of nonspecific carbohydrate hydrolases, which act on sucrose, galactose and maltose, permitting trehalose determination in biological samples, such as insect hemolymph and free cell extracts among others. 3. The enzyme was stable in 50 mM maleate buffer, pH 6.2, at -8 degrees C for at least 6 months and could be used to determine trehalose in the range of 6 to 30 nmol. 4. Immobilization of the enzyme was achieved by covalent linkage to spherisorb-5NH2 (spherical silica gel). Retention of total catalytic activity averaged 32 per cent . 5. The reactor, stored for one month at -5 degrees C, retained 98 per cent of its initial immobilized activity. 6. This immobilized form of the enzyme could be used routinely for specific determinations of trehalose