Characterization and application of tannase produced by Aspergillus niger ITCC 6514.07 on pomegranate rind

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.

Periplasmic trehalase from Escherichia coli: characterization and immobilization on spherisorb

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

Barley oxalate oxidase immobilized on zirconia-coated alkylamine glass using glutaraldehyde.

A method for immobilizing barley oxalate oxidase to zirconia coated alkylamine glass through the process of glutaraldehyde coupling has been described. The immobilized enzyme retained 97.2% of the specific activity, with a conjugation yield of 6.63 mg/g support and showed an increase in optimum pH. The Km value of immobilized enzyme was unaltered but Vmax was decreased compared to free enzyme. The conjugated enzyme was stable at 4 degrees C for 2 years. A number of inorganic ions and metabolic substances did not denature the immobilized enzyme. The clinical importance of this work is demonstrated.

Immobilization of amyloglucosidase.

Enzymatic hydrolysis of starch for the production of glucose syrups of various compositions has assumed considerable commercial significance due to the extensive application of these syrups in food and beverage industries. Hydrolysis of starch to glucose involves liquefaction of the gelatinized starch with acid or thermostable alpha-amylase followed by saccharification to glucose by amyloglucosidase. Large scale saccharification of liquefied starch to glucose using soluble enzyme is time consuming and requires 48-72 hr at pH 4.5 and 55-60 degrees C. Since, by replacing soluble amyloglucosidase with immobilized enzyme, it is possible to reduce the conversion time, several methods have been tried to obtain a highly active and stable immobilized preparation capable of converting high concentrations of liquefied starch to glucose. However, till today, immobilized amyloglucosidase has not found industrial application as no immobilized system has shown high temperature stability and conversion efficiency comparable to that of the soluble enzyme.