## 4 Discussion
Under these optimal conditions for the enzyme activity, the crude extracellular amylase unit activity of NW2 was found to be 0.85 U/mL. The unit activity of this enzyme is somewhat consistent with previous reports on crude amylase activity from thermophilic _Anoxyobacillus_ species [23]. Numerous studies have demonstrated that extracellular amylases isolated from various bacterial species possess significant potential for industrial-scale applications. Amy-lases derived from the thermophilic bacterium _B. licheniformis_ exhibit excellent amyloid properties and have been successfully applied in the biodegradation of food waste [45]. Moreover, amylases from different bacterial sources display remarkably high thermal optima, including 135 \({}^{\circ}\)C for _B. subtilis_[46] and 85 \({}^{\circ}\)C for _Rhodothermus marinus_[47]. Other thermophilic bacteria, such as _Bacillus calolyticus_[48] and _Geobacillus thermoleocorans_[49], exhibit peak enzymatic activity at around 70 \({}^{\circ}\)C, highlighting the wide range of thermostability among bacterial amylases. The thermostability and broad pH tolerance of these enzymes reduce the need for cooling steps and pH adjustments, improving process efficiency and cost-effectiveness. The bacterial species _T. caldiprotelolytica_ (formerly _A. caldiprotelolytica_) is already known for its production of extracellular proteases rather than amylase [40]. To date, only a single study has reported the production of extracellular amylase by this bacterial species [50]. However, that study lacks comprehensive details regarding the activity of the extracellular amylase produced by _A. caldiprotelolytica_. Furthermore, the two known bacterial strains most closely related to the NW2 isolate have not provided detailed information regarding their amylase activities [40; 50], suggesting the need for further studies to investigate the potential of producing extracellular amylase from this species. The presence of different metal ions in the enzyme reaction mixture can significantly affect the activity and stability of thermostable amylases [51]. The crude amylase activity of the NW2 isolate was significantly enhanced by Ca\({}^{2+}\) and Mn\({}^{2+}\) ions. The Ca\({}^{2+}\) ion has been reported to play a vital role in enhancing the activity of most of the thermostable amylases by maintaining the structural integrity and catalytic efficiency at higher temperatures [52]. However, it has been reported that the activity of some amylases is independent of Ca\({}^{2+}\)[14]. Moreover, the Hg\({}^{2+}\) ion strongly inhibited the activity of crude amylase of NW2. This may be due to binding to the active site of the enzyme or altering the correct three-dimensional conformation of the enzyme. Cassava starch is extensively utilized across diverse industries, including food processing, textiles, and bioethanol production. However, its hydrolysis is often associated with high operational costs, primarily due to the energy-intensive nature of conventional processing methods. Recent studies have demonstrated the successful application of microbial amylases in the production of bioethanol from raw cassava starch [53]. In this context, the extracellular amylase produced by the NW2 isolate in the present study exhibited strong hydrolytic activity toward raw cassava starch, highlighting its potential for use in both the food and biofuel industries, where efficient and rapid starch degradation is essential. Furthermore, the enzyme's stability under moderately alkaline conditions enhances its applicability in the detergent industry, where alkaline-tolerant amylases are required. To the best of our knowledge, this is the first report of a _T. caldiproteolyticus_-like strain from Sri Lankan geothermal springs exhibiting a remarkable extracellular amylase activity. The NW2 isolate is a Gram-positive, rod-shaped, and catalase-positive bacterium. These morphological and biochemical characteristics are commonly associated with well-known amylase-producing bacteria [54].