CONTACT-SORPTION DRYING OF PENICILLIUM-BILAII IN A FLUIDIZED-BED DRYER

A fluidized bed dryer and drying system have been designed, constructe d and operated to produce a powdered formulation of the fungus Penicil lium bilaii. The dryer includes an air-shear atomizer and rotatable ai r vibrator to produce particles which are evenly coated with P. bilaii . The drying system included a humidifier, oven, vacuum pump and instr umentation to ensure precise control of operating conditions. Instant skim milk powder was found to be the best particle source for fixing t he spores due to its solubility in water, its highly porous nature and because its moisture isotherms were similar to those of the spores. T he dryer was operated at 35 degrees C to maximize the drying rate whil e still preventing thermal death of the spores. The fluidizing air was best provided at an RH of 30%, thereby producing skim milk/spore part icles with just the right amount of moisture to ensure long term stora ge viability. Storage under refrigeration conditions showed little lon g term decline in spore viability after 3 months of tests. Room temper ature storage demonstrated a small decline rate in spore viability wit h little significant change if held at room temperature for a few days .