A preliminary investigation of some of the factors affecting the percentage germination of lyophilized conidia of Aspergillus niger Van Tieg

• Main Author: Anastasiou, Joan Diane
• Language: English
• Published: University of British Columbia 2012
• Online Access: http://hdl.handle.net/2429/41208

Variations of the techniques and materials used during lyophilization procedures are considered for their effect upon the percentage viability of the conidia of Aspergillus niger (van Tieg.) after freeze-drying. Of the factors investigated, those affecting percentage survival are: (1) Age of the culture from which the conidia are harvested. At 24-26°C., maximum survival occurs after two to six days of incubation. (2) The temperature at which the culture is incubated. A temperature of 6°C. slows the loss of viability after lyophilization. (3) The carrier in which the conidia are dried. Solutions containing 20% sucrose allowed the best survival of the diluents tested. 0.5% ascorbic acid depressed viability immediately after drying and after 13 months storage. (4) Degassing the spore suspension before freezing it. This treatment increased survival after lyophilization. This is not a surface phenomenon. (5) The length of time and the temperature at which the conidia are suspended before being frozen. A long period and a high temperature of spore suspension produces a rapid loss of viability after drying. (6) The general method of lyophilization. The Edwards centrifuge method of freeze-drying produces better survival than either of the other two methods described. Those factors which do not significantly affect conidial survival are: (1) Concentration of conidia in the drying suspension. Only a narrow range of dilutions were tested. (2) The length of time from 5 minutes to 10 hours that the suspension is frozen at -50°C. before evacuating. === Science, Faculty of === Botany, Department of === Graduate