Isolation and identification of Bacillus sp. with high protease and amylase activity from Sunchang traditional Kochujang

To improve the quality of traditional kochujang, strains with high protease and amylase activity were isolated and identified from Sunchang traditional kochujang. Twenty-three strains strongly producing protease and 16 strains strongly producing α- and β-amylase were isolated by using 1% isolated soy protein agar medium and 2% starch agar medium, respectively. Protease activities of the IA7, I5, and IA2 strain were 22.5, 21.2, and 20.6 unit/mL, respectively, and were higher than those of the other strains. Stains with high α-amylase activity included K9 (967.8 unit/mL), K14 (828.3 unit/mL), K13 (662.5 unit/mL), K8 (601.5 unit/mL), and K11 (405.9 unit/mL). The β-amylase activity of the K11 strain was the highest, 34.3 unit/mL, among the isolated strains. Based on morphological, physiological properties, and API 50CHB-kit test for assimilation of 49 carbohydrates, 8 strains selected according to protease, α-amylase, and β-amylase activities were tentatively identified as Bacillus megaterium (IA2), Bacillus subtilis (IA7, I5), Bacillus amyloliquefaciens (K8, K9, K11, and K13), and Bacillus stearothermophillus (K14). The IA7, I5, and K11 strains were finally identified as B. subtilis (99% ID) based on 16S rDNA sequencing.