Lactophenol

Lactophenol is a mounting medium used in mycology to clear, fix, and preserve fungal specimens for light microscopy. It is a viscous solution traditionally based on phenol (carbolic acid), lactic acid, and water, and is sometimes augmented with glycerol to adjust viscosity. A common variant is lactophenol cotton blue (LPCB), which adds cotton blue dye to stain fungal cell walls for improved contrast.

Phenol in lactophenol provides antiseptic fixation and structural preservation, helping to kill the specimen and maintain morphology. Lactic acid acts as a clearing agent, aiding in the visualization of cellular details by reducing turbidity, while the accompanying solvent and glycerol help to achieve an appropriate refractive index and mounting consistency. When cotton blue is included, the stain binds to chitin in fungal walls, producing blue structures that enhance the visibility of hyphae, conidia, and other features.

Lactophenol is widely used to mount fungal structures for identification and study in clinical, environmental, and plant-pathology contexts. It enables long-term preservation of slides and facilitates morphological assessment under standard light microscopy.

Safety considerations are important: phenol is caustic and toxic, requiring use in a fume hood or well-ventilated area with appropriate personal protective equipment. Spills and waste should be managed according to institutional chemical safety guidelines.

Commercial lactophenol and LPCB formulations are commonly available, and laboratories may prepare their own solutions following established recipes. Storage is typically at ambient temperature and away from heat or direct light, with containers kept tightly sealed to prevent evaporation.