Pichia angusta

Pichia angusta (synonym Hansenula polymorpha) is a yeast species primarily recognized in agriculture for its role as a spoilage agent of stored agricultural commodities. Unlike typical plant pathogens that target living vegetation, this fungus functions as a saprotroph, thriving on nutrient-rich substrates such as harvested grains and fruits.

This yeast organism commonly infests cereal grains, legumes, and perishable produce during long-term storage in elevators or warehouses. Its ability to metabolize various carbon sources under fluctuating environmental conditions makes it a persistent challenge for the grain processing and storage industries.

The signs and symptoms of infestation include a distinct yeasty or alcoholic odor emanating from the grain bulk and the visible development of whitish or cream-colored fungal colonies on the surface of seeds. The metabolic activity of these yeasts leads to the fermentation of sugars and degradation of proteins, which significantly reduces the nutritional quality and industrial value of the crop.

Conditions favorable for the development and spread of Pichia angusta are characterized by high substrate moisture levels and moderate temperatures (20–30°C). The fungus spreads rapidly through contaminated dust, equipment, or handling tools. Poor airflow within storage facilities creates micro-environments where the yeast can proliferate, leading to localized heating and further deterioration.

Effective prevention and control strategies are essential to maintain the integrity of the harvest. These include strict adherence to moisture management protocols before storage, regular sanitation of facilities, and the implementation of active aeration systems. Constant monitoring of temperature and humidity remains the most critical practice to suppress the growth of this yeast and prevent substantial post-harvest losses.