Continuous Freeze-Drying of Serratia marcescens

Survival During Storage of Serratia marcescens Dried by Continuous Vacuum Sublimation1

“…The results compiled in table 2 demonstrate clearly that the most favorable moisture content for storage survival of (a) and (b) is between 0.5 to 0.6 per cent. When dried to a moisture content above 2 per cent, the organism does not survive a 6 weeks' storage at 50 C. Entirely contrary is its drying recovery (Maister et al, 1958). Evidently owing to the greater heat application required for producing moisture levels below 2 per cent, cells of weak biological condition are inactivated, whereas stronger cells survive the drying and storage condition better.…”

“…In all experiments, the protective material used in fortification was the mixture of ingredients proposed by Naylor and Smith (1946), except the dextrin portion was omitted. The fortified cell suspensions were rapidly frozen to uniform spheres in an ascending type "pelleter" (Maister et al, 1958). The frozen spheres or pellets were then continuously freeze-dried in the "Fort Detrick Continuous Dryer" (Rhian ct al., 1957), employing experimental modifications which had permitted the development of a readily reproducible process.…”

Pilot-Plant Production of Ground Serratia marcescens

“…Complete details of the drying studies conducted in the continuous freézedryer have been given by Maister, Figure 2. Frozen pellets from fermented medium or centrifuged concentrates were dried in a continuous freeze-dryer Heger, and Bogart (5). Only a summary of their findings is given here.…”

Less-Common Drying Methods

“…A pilot-scale screen-belt unit has been described for drying a representative bacterium, Serratia marcescens, with a bank of radiant heaters arranged to give a logarithmic heat-flux profile along the heating zone. (36) At optimum conditions, the belt (3 m long X 0-28 m wide) running at 0-6 m/h yielded 50 g/h of dried bacterium with 80% or more cells still viable. Chopped meats and vegetables can be rotary dried in a steam-jacketed tube enclosed in the vacuum chamber; a commercial-sized unit would have a nest of such tubes, all serviced with a single set of feed and discharge vacuum-locks.…”