Partial characterisation of alpha-amylase enzymes produced by thermophilic Bacillus isolates

In this study, three thermophilic Bacillus sp. bacteria were isolated from soil samples taken from Çukurova University campus area. The isolated bacteria were named as Bacillus sp. SD1, SD2 and SD3, respectively. Isolation and partial characterisation of α-amylase enzymes produced by the bacteria were carried out. The optimum temperature values at which the enzymes showed optimum activity were determined as 50 ℃ for SD2 and SD3 isolates and 40 ℃ for SD1 isolate. SD1 α-amylase showed its optimum activity at pH 8.0, while SD2 and SD3 α-amylases showed their optimum activity at pH 6.0. After inoculation of bacteria into the media, SD2 α-amylase reached the highest activity level at 24 h, while SD1 and SD3 α-amylases reached at 48 h. All three enzymes completely retained their activities after 15 min pre-incubation at 30 and 40 ºC. After 50 ºC, the remaining activity losses occurred after 15 min pre-incubation, and they lost most of their activity at 100 ºC. Among the chemicals, Ca, Mg and Co showed stimulatory effect on all three enzymes at different rates, while K and EDTA showed inhibition effect. 16S rDNA sequencing analysis revealed that the strains of Bacillus sp. SD1 and SD2 were highly similar. Keywords: Bacillus sp., alfa-amylase, isolation, characterization