## 1 Introduction  
Many industrial processes use large amounts of expensive and hazardous synthetic chemical catalysts, which pose serious risks to the environment and human health. In response, biocatalysts are receiving greater attention as sustainable and eco-friendly alternatives with superior selectivity, efficiency, and cost-effectiveness [1, 2]. Microbial extremozymes are a unique class of biocatalysts that exhibit remarkable stability and catalytic efficiency under extreme environmental conditions, such as elevated temperatures, extreme pH, and high salinity [3, 4, 5]. Among the various extremozymes, thermozymes produced by thermophilic bacteria are of particular interest in modern biotechnological industries due to their high thermostability, which is essential for maintaining enzymatic activity under the harsh conditions of industrial processes [6]. Thermophilic bacteria are broadly classified based on their optimal growth temperatures into moderate (optimal growth 45-80 \({}^{\circ}\)C) and extreme (optimal growth \(>\) 80 \({}^{\circ}\)C) types [7, 8]. Bacterial thermozymes, such as amylases, proteases, lipases, polymerases, cellulases, and chitinases have gained significant industrial importance due to their efficient activity under extreme conditions [6].  
Among microbial extremozymes, thermostable amylases are of commercial significance in various industries representing approximately 25% of the global enzyme market. These amylases hydrolyze starch at elevated temperatures, eliminating the need for energy-intensive cooling systems and contributing to substantial reductions in processing costs [9]. They offer promising operational advantages across a range of industrial sectors, including food processing, pharmaceutical, pulp and paper, textile manufacturing, detergent, biofuel production, bioremediation, and waste management [6, 10, 11]. Thermostable amylases are primarily produced for industrial applications by several well-characterized bacterial genera, such as _Bacillus_[12] and _Anoxyobacillus_[13, 14, 15], due to their high enzymatic yield, remarkable thermostability, and scalability. Moreover, numerous studies have been conducted on the isolation and characterization of bacterial species that produce thermostable amylases from diverse ecological niches. Thermostable amylases have been identified in species, such as _Streptomyces erumpens_, _Thermobifida fusca_, and _Bacillus_ strains isolated from soil environments [16, 17, 18, 19]. In the ongoing search for excellent thermostable amylases for industrial applications, several researchers have successfully isolated and characterized thermostable amylases from thermostable bacteria that thrive in thermal spring environments [15, 20, 21, 22, 23, 24].  
Despite significant advancements in the identification of novel extremophiles for industrial applications, the geothermal ecosystems of Sri Lanka remain largely underexplored. A study has been reported that explored the microbial diversity of a geothermal spring in Sri Lanka [25]. However, this study did not report the presence of well-known thermostable amylase-producing bacteria. This highlights a significant gap in the understanding of Sri Lanka's geothermal microbial diversity in the context of industrially important extremozymes. Therefore, the present study was conducted with the objective of the isolation and molecular characterization of thermophilic bacteria producing extracellular amylases from Sri Lankan geothermal springs and assessing their potential for industrial applications.