Amylase Production by Aspergillus niger immobilized in Microporous Calcium Alginate Gel Beads

Abstract

Microporous calcium alginate gel beads were investigated as potential solutions to mass transfer limitations in immobilized cultures. The beads were prepared by gelling mixtures of sodium alginate and fillers (starch or granulated sugars) in calcium chloride solution. The resulting beads were cured in the same solution, during which the fillers leached out of the beads thereby creating micro-pores in the beads (microporous beads). The effectiveness of the microporous beads in improving amylase production by Aspergillus niger LC 269109 was investigated. Spores of A. niger were immobilized in the microporous beads and used for batch alpha amylase and gluco amylase production. Amylase production by the A. niger immobilized in the microporous beads were significantly higher (p<0.01) than the values obtained with the conventional calcium alginate gel beads. Under all the conditions investigated, gluco-amylase activities were significantly (p<0.01) higher than the alpha-amylase activities. Under the optimum conditions of inoculum concentration (1.0 × 105 spores/ml), pH (6), temperature (35°C), bead diameter (3 mm) and calcium chloride concentration (1.5%), the gluco-amylase and alpha amylase activities were 11.98 U/ml and 6.7 U/ml respectively, which were significantly higher (p<0.05) than the 7.8 U/ml and 3.2 U/ml obtained with the conventional gel beads.