Chapter V-5 - Fungi: Preservation of cultures

Abstract

This chapter discusses preservation of microbial cultures. Storing fungi, at ambient temperatures rather than in refrigeration, may require fewer resources than any other preservation strategy. Storing culture, slants under a layer of sterile mineral oil, is one of the oldest, simplest and least expensive methods for long-term culture preservation. Cultures kept under mineral oil may remain viable for decades. Pathogenicity of entomopathogenic fungi may be undiminished after several months of storage. Storage of metabolically inactive fungi under sterile distilled water may be least technologically demanding of any preservation techniques. Lyophilization may be one of the most widely used technologically sophisticated approaches to preserve fungal germplasm and is the primary technique used in most general service culture collections. Standard domestic freezers might seem to be an ideal and economical tool for keeping frozen cultures. The use of anhydrous silica gel crystals as a carrier for culture propagules is limited to aerobic bacteria and fungi that grow on solid culture media. The choice of cryoprotectant determines the temperature, the heat of fusion, at which the cryoprotectant freezes with a strongly exothermic reaction. It is observed that the laboratory that relies on nitrogen storage facilities has made a long-term and expensive commitment to maintain cultures perceived as having a very high intrinsic value.