Abstract

Geobacillus kaustrophilus PW11, Geobacillus thermoleovorans PW13 and Geobacillus toebii PS4 were isolated form Tattapani hotspring of Himachal Pradesh, India and characterized for extracellular amylase activity. All the three Geobacillus spp. exhibited thermophilic amylase activity, which was predominantly extracellular. The activity was optimum at 90°C and pH 7.0. Interestingly, no amylase activity was observed at temperature less than 40°C, indicating its thermophilic nature. Moreover, pre incubation of enzyme at 100°C enhanced the amylase activity. The specific activity of amylase of PW11, PW13 and PS4 was 3898, 3597 and 3289 U mg-1, respectively at 90°C and pH 7.0. Starch, amylopectin and dextrin were observed to be the best substrates for amylase activity. Further, amylase activity of PW13 and PS4 remained unaffected in the presence of Triton X 100 (0.5%), but decreased by 40% in case of PW11 isolate. Among the metal ions tested, Mn2+, Co2+ and Fe2+ enhanced the amylase activity of PW11, PW13 and PS4 by 2-5 folds. While Hg2+ (1mM) strongly inhibited enzyme activity of PW13 and PS4, Cd2+ completely inhibited amylase activity of PW11. Amylase activity of PW13 and PS4 was enhanced by 2-2.5 folds in the presence of EDTA (5 mM). The thermophilic amylase activities of PW11, PW13 and PS4 are highly advantageous for downstream industrial applications.

Keywords: Thermophilic, amylase, extracellular, geobacillus, tattapani, thermophiles, hotspring.

Graphical Abstract