Studies On Protectants For Preparation And Formulation Of Bacillus Subtilis Bs-208

During the spray dry process, Bacillus subtilis Bs-208 has high thermal death rate. Also has low survival rate in liquid and powder formulation during stocking. This shortened the shelf life of Bs-208 product. In this thesis, studies on thermal protectant, liquid and powder deposit protectant for Bs-208 were carried out through orthogonal design and storage stability test. Some protectants combinations showed higher efficiency to increase the spore survival rate in preparation and formulation.Through single factors screening and two rounds orthogonal designed experiments, a better thermal protectant prescription for Bs-208 was found out. It is 0.10%PEG4000, 0.30%sucrose and 0.20%NaCl. This protectant can increase 18.10% living spore yield under 75℃.Three good liquid protectants were acquired through 10 single-factors test such as NaCl concentration selection and progressive orthogonal experiments. The most efficient protectant, 8.00%NaCl and 1.00%sodium acetate, increased 22.53% survival rate in liquid formulation under 54±2℃for 2 weeks.Through comparing the promotion survival rate of the Bs-208 by sucrose and other 11 compouds and two rounds orthogonal tests, two good powder protectants combinations were selected for further research. The better one, 5.00%NaCl, 2.50%sucrose and 1.25% Sodium benzoate, increased survival18.72% rate under 54±2℃for 2 weeks.This thesis also had also investigated the survival rate fluctuation of Bs-208 formulations with or without protectants under 54±2℃and 40±2℃. The results showed that the survival rates of liquid and powder formulations decline faster without protectants under two temperatures. Bs-208 has higher survival rate in both formulations with protectants.