Enhancement of Viability for Staphylococcus Aureus During Freeze-Drying Using the Response Surface Methodology

摘要

Response surface methodology (RSM) was used to optimize a protective agent for enhancing the cell viability of Staphylococcus aureus during freeze-drying. Using a previous Plackett-Burman design, it was found that sodium glutamate, trehalose, L-cysteine hydrochloride and bovine serum albumin were the most effective freeze-drying protective agents for S. aureus. Through the comparative analysis of single protectant, the complex protective agents show better effect on the S. aureus viability. The paper was carried out by Box-Behnken Design to determine the optimum levels of these four protective agents to seek for maximum viability of S. aureus during freeze-drying. The experimental data allowed the development of an empirical model (P<0.0001) describing the inter relationships between the independent and dependent variables. By solving the regression equation, and analyzing the response surface contour and surface plots, the optimal concentrations of the agents were determined as: 15.73% sodium glutamate, 3.43% trehalose, 0.50% L-cysteine hydrochloride, 0.47% bovine serum albumin. S. aureus freeze dried in this medium obtained a cell viability of up to 96.78%.