Production and characterization of thermostable α-amylase and xylanase from thermobacillus sp. vo15 and bacillus licheniformis. vo14.

Abstract

Thermophilic strains VO15 and VO14 were isolated from the hot-spring water of Billoris (Sağlarca), Siirt in Turkey, were used in this work. The study was aimed to produce and determine the optimum condition for extracellular α-amylase and xylanase by thermophilic bacteria under submerged fermentation (SmF). The optimum condition for production α-amylase by SmF, for Thermobacillus sp.VO15 and B.licheniformis VO14, time of incubation recorded at 48 and 24 hours (12.53 and 15.98 U/mg), temperature 40 and 45°C and pH 6.0 and 7.0, respectively. The optimum condition for production xylanase, for Thermobacillus sp.VO15 and B.licheniformis VO14, time of incubation recorded at 24 hours for both (28.24 and 32.52 U/mg), temperature 45 and 40°C and pH 6.0 and 5.0, respectively. The maximum α-amylase production by Thermobacillus sp and B.licheniformis were found with ammonium sulfate (117,6%) and yeast extract (122,44%), respectively. The maximum α-amylase and xylanase production were obtained with Tween-40 for both bacteria. Various parameters such as temperature and pH, temperature and pH stability, NaCl, detergents, surfactants and metal ions on influence of enzyme characterization were tested. In addition degradation of different starches by α-amylase was assayed. Temperature values (50ºC - 110ºC) were examined to compare the differences of the stabilities. The α-amylase produced by Thermobacillus sp.VO15, at 110ºC keep more than 95% and 80% of its activity after 30 and 240 min, respectively. α-amylases were strongly inhibited by Cd+2 and Hg+2. Both enzymes activated by Co2+.