Abstract:

A highly efficient alginate-degrading microorganism was isolated from rotten seaweed through several cycles of
enrichment and domestication in liquid medium containing alginate as the sole carbon source. According to morphological,
physiological characteristics and 16S rRNA gene sequence analysis, the strain was identified as Bacillus weihaiensis Alg07.
Based on the results of single factor experiments and orthogonal array experiments, the optimal liquid fermentation medium
contained 9 g/L of alginate, 1 g/L of peptone, 3 g/L of yeast exact, 5 g/L of NaCl, 1 g/L of MgSO4·7H2O, 5 g/L of KCl and
4 g/L of CaCl2. The strain was cultured at 30 ℃, pH 6.5 and 180 r/min for 24 h in 40 mL of the medium using a 250-mL
flask, and the inoculum concentration was 0.5% (V/V). Under these optimal conditions, the activity of alginate lyase was
significantly increased from 35 U/mL to 563 U/mL, indicating a 16-fold increase compared with that before optimization.

Key words: alginate lyase, screening, identification, Bacillus, fermentation optimization