CONTINUOUS SYNTHESIS OF THERMOSTABLE ALPHA-AMYLASE BY BACILLUS CELLS IMMOBILIZED IN CALCIUM ALGINATE

The late exponential cells of Bacillus immobilized in calcium alginate were able to synthesize extracellular thermostable-alpha-amylase continuously. The enzyme production with respect to cell concentration in the gel bead as well as with cell-immobilized bead inoculum was optimized. The immobilized cells (containing 10(9) cells per bead), at 10% bead inoculum size, produced alpha-amylase consistently over 10 repeated cycles, and the activity was in the range of 250 units in all the cycles. Continuous production of the enzyme was achieved in a packed-bed reactor with a productivity of 100 Kunits l-1 h-1, which gradually declined to 36 Kunits l-1 h-1 in 400 h.