<![CDATA[Abstract. Sarlan, Arfah RA, Karim A, Anita, Ahmad A, Taba P, Karim H, Larekeng SH, Rampisela DA, Ladju RB. 2025. Screening and characterization of thermostable α-amylase-producing microbes from Karedhe North Buton Hot Springs, Indonesia. Biodiversitas 26: 6513-6522. This study aimed to screen and characterize thermophilic α-amylase-producing bacteria from samples collected at Karedhe hot springs. A total of 23 bacterial isolates were obtained, where 8 isolates showed amylolytic activity. Amylase activity was assessed by iodine staining, which showed significant starch hydrolysis, indicated by clear zones around bacterial colonies. The results showed that isolate SRL40-1-3 had the largest clear zone (4 cm), while SRL40-2-1 produced a clear zone of 5.1 cm, indicating their potential for efficient starch degradation. Additionally, biochemical tests revealed distinct metabolic profiles, with only SRL40-1-3 able to use citrate as a carbon source. Specifically, isolates SRL40-1-3 and SRL40-2-1 were identified as Enterobacter sp. and Enterobacter hormaechei, respectively, based on molecular analysis. Further optimization studies showed that the optimal starch and CaCl2 concentrations for enzyme production were 1.25% and 0.12%, respectively, for SRL40-1-3. The optimum fermentation times were 42 h for SRL40-1-3 and 45 h for SRL40-2-1. In line with the results, the characterization of crude enzyme α-amylase showed that the optimum pH for both isolates was pH 6 at 50°C. Aside from pH, the optimum starch concentrations for crude enzyme in SRL40-1-3 and SRL40-2-1 were 0.015% and 0.01%, respectively. These results indicate that thermophilic bacteria from Karedhe hot springs have potential applications in industries requiring efficient starch degradation, such as bioethanol production and food processing.]]>
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