Isolation and screening of amylase producing thermophilic spore forming Bacilli from starch rich soil and characterization of their amylase activity

Abstract

Thermostable amylases are the most important enzymes in present with potential industrial applications. The main objective of this study was to isolate and characterize thermophilic amylases from Bacilli found in starch rich soil. Amylase producing bacilli were isolated and their enzymes were also characterized. Effect of temperature, pH, substrate and salt concentration on amylases activity were determined. All amylases produced by different isolates were hydrolyzed greater than 91% of starch after 60 h of fermentation. There was no significant (P ≥ 0.05) variation in enzyme productivity along with fermentation time. Amylase producing isolates were designated as Isolate-1, Isolate-2, Isolate-3, Isolate-4, Isolate-5 and Isolate-6. Amylases activities of all isolates were reached their optimum at 60°C. Amylases from all bacilli isolates were shown hydrolysis capacity of starch ranging from 91.4 to 95.7%. The optimum enzyme activity of amylase from Isolate-2 was extended from pH 7 to 8 with starch hydrolysis efficiency of 98% but other isolates enzyme activity reaches 99.5 to 100% at pH 8. The crude amylase extract has an activity with inversely proportional with substrate concentration. The bacterial dry weight increases as the course of incubation time increases and NaCl concentration greater than 5 molar significantly decreases the activity of the crude amylase extract. Amylases of this finding with thermophilic, alkalophilic and halophilic characteristics have wide range of huge potential for industrial applications. Besides, further purification of the crude extract could be conducted to meet thermophilic amylase enzyme requirements of pharmaceuticals and clinical sectors. Key words: Alkalophilic, amylase, bacillus, industrial application, thermostable.