Influence of the immobilization conditions on the efficiency of alpha-amylase production by Bacillus licheniformis

Bacillus licheniformis 44MB82-A cells were immobilized in alginate and agar gels. The optimal immobilization parameters (gel concentration, initial cell quantity, biomass age, bead size and solidification prolongation) were determined. The immobilization procedure was most effective at a gel concentration of 4% using cells from a 12 h culture. The optimal initial cell quantity was found to be 0.6-3.0% in agar gel and 0.4% in Ca-alginate gel with bead sizes of 3.0 and 5.0 mm, respectively. An enzyme yield of 1100 U ml(-1) culture medium was reached in batch fermentation with agar-entrapped cells under optimal conditions. This activity represented 135% of the corresponding yield obtained with free cells. Significant increases (2.2-fold) in the enzyme yields in the fourth cycle of repeated batch runs with cells entrapped in agar gel pellets with bead size 5.0 mm was observed.