SCREENING OF α -AMYLASE FROM RHIZOSPHERIC SOIL ISOLATES

Amylases are crucial hydrolytic enzymes with wide industrial relevance, particularly in food processing, textiles, paper manufacturing, and biofuel production (Gupta et al., 2003; Ray et al., 2015). Among them, α-amylase is distinguished by its capacity to cleave internal α-1,4-glycosidic linkages in starch, enabling rapid saccharification under mild conditions (Pandey et al., 2000). This study aimed to isolate and characterize α-amylase-producing bacteria from rhizosphere soils of Shivamogga District, Karnataka—a region within the Western Ghats known for its rich microbial diversity and endemism (Singh et al., 2016; Jaiswal et al., 2020). Using serial dilution, starch agar screening, and Gram staining, 25 bacterial isolates were obtained, with six demonstrating starch hydrolysis through clear halo zones. The highest enzyme-producing isolates (SSCMBSAR3 and SSCMBSAR5) were identified as Gram-positive bacilli, likely belonging to the Bacillus genus, corroborating their reputation as prolific amylase producers (Gupta et al., 2003; Ajayi & Fagade, 2006). One Gram-negative coccus (SSCMBSAR2) also exhibited notable activity, highlighting underexplored microbial groups like Neisseria and Pseudomonas (Madigan et al., 2017). Quantitative enzyme assays using the DNS method (Miller, 1959; Chi et al., 2009) revealed peak α-amylase activity at 48 hours of incubation and optimal substrate concentration at 400 mg starch, followed by substrate inhibition at higher concentrations—demonstrating a bell-shaped kinetic profile consistent with Michaelis-Menten dynamics (Segel, 1993). The co-detection of protease activity indicates a need for further purification or genetic modifications to eliminate non-specific enzymes (Haq et al., 2010). This study underscores the rhizosphere as a fertile bioprospecting niche and affirms the industrial potential of both Gram-positive and Gram-negative soil bacteria in enzyme biotechnology.