Isolation, identification of thermophilic bacteria isolated from thermal springs of nevşehir-kozakli, purification and characterization of α-amylase enzyme from Bacillus licheniformis SO7

As part of this thesis research; Isolation and molecular characterization of thermophilic bacteria was performed on the water samples taken from the thermal water sources of Nevşehir-Kozaklı. As a result of this study, it was detected that the isolates had a similarity to Bacillus licheniformis and B. paralicheniformis at a rate of 99%. B. licheniformis SO7 strain which gives the highest amylase activity as a result of the petri dishes from these isolates was selected, extracellular α-amylase enzyme from these isolates was purified in one step by using starch affinity method and characterized biochemically. The molecular weight of the enzyme purified 1,95 fold with 28,65% efficiency was found to be about 83,17 kDa by using SDS-PAGE gel electrophoresis method. For the α-amylase enzyme it was determined that; the optimum pH was 7,0 and the optimum temperature was 90°C. The amylase enzyme seemed to be stable in the broad alkaline pH range (pH 7,0-11,0). It has been found that the enzyme protects approximately 80% of its activity after 120 min at temperature of 80°C. It has been determined that amylolytic activity of B. licheniformis SO7 α-amylase enzyme increased in the presence of some surfactants such as Tween-20 and Triton X-100. The enzyme, which exhibits a high stability towards organic solvents, was found to retain 73% of its activity in the presence of 30% acetone. It was determined that K+ ion increased the activity and in the presence of EDTA the enzyme stability was protected at 86%. In addition, it was identified that the CaCI2 compound increased the α-amylase enzyme activity. The highest substrate specificity for the α-amylase enzyme was determined as rice starch. The KM and Vmax values for B. licheniformis SO7 α-amylase enzyme were respectively found to be 3,24 mg / mL and 204,08 mmol.mL-1 min-1.