COMPARISON OF AIR-DRYING METHODS FOR EVALUATING THE DESICCATION TOLERANCE OF LIQUID CULTURE-PRODUCED BLASTOSPORES OF PAECILOMYCES-FUMOSOROSEUS

Various drying methods were tested to identify a standard procedure fo r evaluating the desiccation tolerance of liquid culture-produced blas tospores of Paecilomyces fumosoroseus. Since our work is focused on op timizing fermentation conditions for the production of P. fumosoroseus , the criteria for selecting a drying method included ease of use, mod erate spore survival after drying and limited variation in spore survi val. Three air-drying methods were tested: P. fumosoroseus blastospore s mixed with silica gel, with sand, or with diatomaceous earth. Humidi ty controlled drying was used in the diatomaceous earth drying method. Blastospore survivals after drying were 19% (C.V. range, 32 to 45%), 82% (C.V. range, 26 to 43%), and 2% (C.V. range 32 to 50%) for the sil ica gel, sand, and diatomaceous earth methods, respectively. Blastospo res dried using the silica gel and sand methods had been rinsed in 0.7 M poldyethylene glycol before drying and rehydrated in the same solut ion for determination of survival. The variation observed within each method was similar. The silica gel drying method was selected as most appropriate for our studies based on moderate blastospore survival (19 %) and ease of use.