Preparation of Bacillus megaterium NCT-2 freeze- dried agent by using response surface methodology

Vacuum freeze-drying method was used to prepare B.megaterium NCT-2 agents,cryoprotectants were optimized using response surface methodology after single factor experiment.Centrifugal conditions,suspension substrate,selection and formulation of cryoprotectants,rehydration water were studied on the impact of survival rate.The results showed that the optimal conditions were 5000 r/min,10 min and fresh media was the better choice as the suspended substrate.Different kinds of water did not had obvious impact on the survival rate after rehydration.Results indicated the optimal amounts of cryoprotectants formula were sucrose 4.51 mg/g,trehalose0.9 mg/g,glucose 9.60 mg/g.The proven survival rate was 91.8%.