Abstract
α-Glucuronidase from Aspergillus niger specific for O-α-D-glucosyluronic acid α-D-glucosiduronic acid (trehalose dicarboxylate, TreDC) was hydrolyzed TreDC to produce D-glucuronic acid. For the application of the α-glucuronidase to D-glucuronic acid production, the enzyme was immobilized on a baked diatomite. The immobilized enzyme treated with glutaraldehyde retained about 60% of the initial activity after repeated uses of 20 cycles. Although the immobilized enzyme completely hydrolyzed 100 mM TreDC, the reaction was significantly inhibited by D-glucuronic acid over 200 mM TreDC. To hydrolyze TreDC completely, the reaction mixture was diluted with buffer to keep the D-glucuronic acid concentration below 300-400 mM. The immobilized enzyme in the diluted reaction mixture hydrolyzed 500 mM TreDC (initial concentration) almost completely to produce D-glucuronic acid. The immobilized enzyme packed in a column continuously produced D-glucuronic acid and the activity of the enzyme remained about 80% of the initial activity after 20 days of operation.
