Comparison of function of immobilized and free Bacillus licheniformis cells in production of alkaline protease

Proteases are an important group of industrial enzymes, which are widely used in different industries such as detergent, leather tanning, pharmaceutical, and food industries. The aim of this study was to immobilize Bacillus licheniformis cells in calcium alginate beads and study of its effects on the amount of alkaline protease production. Effects of several different conditions on stability of the beads were also examined.

Bacillus licheniformis cells were immobilized in calcium alginate beads and were used for production of alkaline protease. The amount of enzyme production was compared in immobilized and free-cell fermentation. Effect of stuffing rate (%) on the enzyme production was studied. Optimum pH and temperature of enzyme activity were also determined. Furthermore, effects of pH, curing time and treating the beads by glutaraldehyde on stability of the beads were examined.

In this study the amount of production and productivity of protease in immobilized cells state showed an increase of 74% and 54% in comparison to free cells state, respectively. The highest amount of the production of the enzyme was obtained in stuffing rate of 5% (v/v). Optimum pH and temperature of the enzyme activity were determined 8 and 65oC, respectively. The highest stability of the beads was observed at curing time of 1 hour at pH of 7.4. Treating the beads by glutaraldehyde was detrimental to their stability.

Use of immobilized cells of Bacillus licheniformis in calcium alginate beads on the one hand, can increase productivity of the alkaline protease in comparison to free cells method, and on the other hand, reduces the cost of the enzyme production because of eliminating the need of preparation of inoculum for the new batches.