Yeasts at Extreme pH Conditions

Some yeast species exhibit remarkable adaptability to extreme pH conditions, thriving in both highly acidic and highly alkaline environments. Acidophilic yeasts are commonly found in ecosystems such as acid mine drainage sites, acidic water environments, volcanic lakes, solfatara fields, and peat bogs, where pH values can drop below 3. These yeasts have evolved specialized mechanisms to maintain intracellular pH homeostasis, including active proton pumps, membrane remodeling, and stress response proteins. In contrast, alkaliphilic yeasts inhabit environments such as soda lakes, saline–alkaline soils, and industrial waste sites, where pH levels exceed 9. Their survival strategies involve ion transport systems, cytoplasmic buffering mechanisms, and metabolic reprogramming to counteract alkaline stress. These extremophilic yeasts play fundamental ecological roles in nutrient cycling, organic matter decomposition, and metal detoxification. Moreover, they offer promising applications in biotechnology, particularly in the production of enzymes, organic acids, and a few bioactive compounds. Acidophilic yeasts have been explored for their potential in bioremediation, bioleaching, and fermentation under low-pH conditions, while alkaliphilic yeasts are valuable for industrial processes requiring stability at high pH, such as detergent production and waste treatment.