Thermostable amylases from thermophilic microbes: advances in production, engineering, and industrial applications

Amylases are essential enzymatic macromolecules widely employed in industrial sectors such as starch processing, textiles, detergents, paper manufacturing, pharmaceuticals, and biomedical research. Among α-, β-, and γ-amylases, thermostable α-amylases from thermophilic microbes show high catalytic activity and structural stability under heat, pH variation, and solvent stress. These properties make them valuable for stable, contamination-resistant, and efficient bioprocesses. Thermostable amylases also hold promise in biomedical fields, including diagnostics, enzyme replacement therapy, and nanocarrier-based drug delivery. This review summarizes microbial sources and production approaches for thermostable amylases, highlighting submerged and solid-state fermentation methods. The discussion also outlines optimization of carbon and nitrogen substrates, fermentation duration, and moisture control strategies that directly influence enzyme yield and activity. Factors governing enzyme yield and stability are analyzed, including nutrient balance, pH, temperature, and moisture. Despite their potential, widespread application remains limited by low native production yields, suboptimal heterologous expression, and functional trade-offs between thermostability and enzymatic activity. Recent advances in protein engineering (rational design and directed evolution), omics-driven strain improvement, and nanotechnology integration provide paths to address these limitations. By integrating these strategies, researchers are achieving enzymes with longer operational lifetimes, higher substrate specificity, and improved reusability under industrial and physiological conditions. These advances highlight the growing relevance of thermostable amylases in industrial biotechnology and biomedical research.