Abstract:

To increase the fermentation titer unit of elastase with immobilized Bacillus licheniformis, the immobilization
process and fermentation characteristics of Bacillus licheniformis were investigated and optimized by single-factor
experiments and response surface methodology. After optimization, a proper immobilization system was determined,
which consisted of polyving akohol (PVA), sodium alginate (SA), calcium chloride and boric acid at a concentration by
mass of 8.22%, 2.27%, 2.42% and 4% respectively. Under the optimized conditions, the activity of elastase produced
from immobilized Bacillus licheniformis reached 386 U/mL, which was 87% of the fermentation yield with free cells. The
immobilized Bacillus licheniformis had good stability, and could be used in fermentation for more than 10 consecutive
batches. These experimental results indicate that the immobilized Bacillus licheniformis prepared by composite gel
entrapment can be used in continuous fermentation process for the production of elastase.

Key words: Bacillus licheniformis, immobilization, fermentation, elastase