Isolation and Screening of High-Potential Bacterial Isolates for Thermostable Amylase Production

Thermostable amylases produced by thermophilic microorganisms represent a promising solution for efficient industrial processes under harsh conditions. In this study, eighty-one bacterial isolates were isolated and screened for thermostable amylase production under solid-state fermentation (SSF) using wheat bran as the substrate. The residual enzyme activity was measured after an incubation at 80 °C for 1 h. Initial (zero-time) activities values varied widely (≈3.5–60.5 IU/gds), reflecting physiological and genetic diversity in amylase expression among the isolates. Thermal stability also differed substantially: while many isolates lost most of their activity after heat treatment, a subset retained high residual activity (> 70%), indicating exceptional thermostability. The ten most promising isolates were no. 76 (87.3%), 63 (83.6%), 16 (81.9%), 2 (81.2%), 45 (80.1%), 12 (77.1%), 66 (75.2%), 40 (74.8%), 18 (74.5%), and 71 (71.6%). Morphological, biochemical, and physiological characterization revealed that all top-performing isolates belong to the genus Bacillus. These findings highlight Bacillus spp. as potent producers of thermostable α-amylases.