Purification and characterization of thermostable agarase from Bacillus sp. BI-3, a thermophilic bacterium isolated from hot spring.

An extracellular agarase was purified from Bacillus sp. BI-3, a thermophilic agar-degrading bacterium isolated from a hot spring in Indonesia. The purified agarase revealed a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, with an apparent molecular mass of 58 kDa. The optimum pH and temperature of the agarase were 6.4 and 70°C, respectively. The activity of the agarase was stable at high temperatures, and more than 50% activity was retained at 80°C for 15 min. Furthermore, the enzyme was stable in the pH range of 5.8-8.0, and more than 60% of the residual activity was retained. Significant activation of the agarase was observed in the presence of K(+), Na(+), Ca(2+), Mg(2+), and Sr(2+); on the other hand, Ba(2+), Zn(2+), Cu(2+), Mn(2+), Co(2+), Fe(2+), and EDTA inhibited or inactivated the enzyme activity. The components of the hydrolytic product analyzed by thin-layer chromatography showed that the agarase mainly produced neoagarobiose. This study is the first to present evidence of agarolytic activity in aerobic thermophilic bacteria.