ANHYDRIOBIOSIS 



21 



Recent investigations of Lion'-^ represent a great advance in 

 the understanding of the process of freeze-drying and the 

 importance of various factors involved. His results and their 

 interpretation give a coherent picture of the process and present 

 a reasonable hypothesis which not only accounts for most of the 

 seemingly unrelated findings reported in the literature, but also 

 allows the prediction of new lines of research and practical 

 applications. 



The basic questions which Lion asked were: when and why 

 do bacteria die during freeze-drying or during subsequent 

 storage? What agent is lethal to micro-organisms during this 

 process? 



To discover the lethal agent he first used 'naked' bacteria, 

 i.e. bacteria suspended in distilled water, so as not to obscure 

 the picture of possible protection by any of the chemical 

 compounds present in the usual media. Most of the work was 



5 6 



Hours 



Fig. 4. Kinetics of death of cells of E. coli during and following freeze- 

 drying. Washed suspensions of E. coli about lO^Vml in distilled water. 

 Between primary and secondary drying, various gases were introduced into 

 ampoules: C = control in vacuum, H = hydrogen, A = air, O = oxygen. 



References p. 29 



