Thermostability and pH Differentiation in Geobacillus Hydrolases: A Comparative Perspective

Abstract Thermostable enzymes are central to high-temperature industrial processes because they combine catalytic efficiency with structural resilience under demanding conditions. Among thermophilic bacteria, Geobacillus has emerged as a prominent source of industrially relevant enzymes, particularly hydrolases such as proteases, lipases, and carbohydrate-active enzymes. Although many individual enzymes have been characterized in detail, comparative synthesis across catalytic classes within the genus remains limited. In this review, we integrate biochemical data and structural evidence to explore whether thermostability in Geobacillus reflects isolated enzyme-specific traits or recurring functional patterns across enzyme classes. Reported Tmax and pHmax values from purified and partially purified hydrolases were systematically compiled to assess class-level tendencies. Temperature optima cluster within a relatively narrow thermophilic range across enzyme groups, supporting high-temperature activity as a common feature within the genus. In contrast, pH optima display clearer functional differentiation, with proteases and lipases consistently shifted toward alkaline values relative to carbohydrate-active hydrolases. Recurrent stabilizing elements, including reinforced hydrophobic cores, expanded electrostatic interaction networks, and a balanced rigidity–flexibility profile, are observed across multiple enzyme classes, indicating shared structural trends rather than independent enzyme-specific variation. By situating catalytic optima within a comparative framework and relating them to shared structural determinants, this review provides a comparative interpretation of patterns observed across Geobacillus-derived enzymes, linking structure, catalysis, and functional adaptation.