title: Optimization of the production and characterization of milk clotting enzymes by Bacillus subtilis natto.
abstract: Suitable medium for production of milk clotting enzyme (MCE) by Bacillus subtilis (natto) Takahashi in submerged liquid-state fermentation was screened, the nutrient factors affecting MCE production was optimized by response surface methodology. The MCE production by B. subtilis (natto) Takahashi was increased significantly by 428% in the optimal medium developed. The MCE was filtered and concentrated by ultrafiltration. The retentate after tandem filtration carried out with the combined membranes of MWCO 50kDa and 5 kDa showed two major bands between 25kDa and 30kDa on SDS-PAGE, and the MCA and MCA/PA improved significantly in comparison with those in the initial broth. The crude enzyme thus obtained showed MCA and MCA/PA ratio of 48,000 SU/g and 6,400, which are commensurate with those (MCA 26,667 SU/g and MCA/PA 6,667) of the commercial rennet. It had optimal pH and temperature at pH 6 and 60°C, and showed excellent pH and thermal stability.
authors: Department of Bioindustry Technology, Da-Yeh University, Changhua, Taiwan.
authors: Fang-Chen
authors: FC
authors: Wu
authors: Chen-Wei
authors: CW
authors: Chang
authors: Ing-Lung
authors: IL
authors: Shih
keywords: Bacillus subtilis natto; Cheese making; Milk-clotting activity; Milk-clotting enzyme; Response surface methodology; Ultrafiltration