Design of a technical method of vacuum freeze-drying for quantitative preservation of Staphylococcus aureus
Objective To investigate a new approach for quantitative preservation of staphylococcus aureus standard strains utilizing vacuum freeze-drying.Methods Staphylococcus aureus lyophilized pellets were prepared using micro-filtration pore membranes under vacuum freeze-drying conditions,and the effects of various factors,including growth curves,screening of single lyophilized protectants,optimal compounding of protectants,vacuum freezing pre-freezing and freezing temperatures,preservation conditions,and expiration dates,on the viability of the lyophilized pellets were investi-gated.Results The growth curve data revealed a logarithmic phase after 4 hours and a stabilizing phase after 16 hours.Single protective agents were selected among sugars,proteins,and antioxidants,and the findings revealed that skim milk,trehalose,and ascorbic acid had the highest rates of bacterial survival(F=6.7,P＜0.05,adj R2=0.785 5).The lyophilized protectant formulation was improved utilizing the response surface approach using skimmed milk(3％),treha-lose(10％),and ascorbic acid(0.75％).The bacterial survival of the lyophilized bacterial tablets could reach more than 90％in the presence of this protective agent,which is more comparable to the projected value.The results demonstrated the effectiveness of of the response surface approach in improving the protectant composition.Bacterial pellets were freeze-dried at-40℃ after being pre-frozen at-20℃(F=147.0,R2=0.982 9,P＜0.001).After 6 months of storage in a re-frigerator at-40℃,the survival rate of bacteria can reach 93.3％,and it can still reach more than 80％after two years(F=79.42,R2=0.969 5,P＜0.001).Conclusion The results demonstrated that lyophilized pellets of Staphylococcus aureus made using the compounded protective agent could accomplish effective quantitative preservation by de-termining the survival rate of the lyophilized pellets.
万方数据
维普
