An alkalophilic strain of Bacillus sp., designated TS-23, was isolated from a soil sample collected at a hot spring (Tainan, Taiwan). During growth in a medium containing 1% soluble starch as the sole source of carbon, the fermentation broth exhibited both pullulanase and amylase activity. Pullulanase and amylase activities were maximal at 65 degrees C. The pH optima were 8.8 to 9.6 for pullulanase and 7.5 to 9.4 for amylase. Under optimal conditions, a crude preparation hydrolysed pullulan, generating maltotriose as the major product. Strain TS-23 was found to produce five amylases (A(c), A(1), A(2), AP(1), and AP(2)), which were visualized by activity staining of proteins that had been separated by native polyacrylamide gel electrophoresis. Both AP(1) and AP(2) had pullulanase activity and A(c), A(1) and A(2) had the ability to adsorb to raw corn-starch. Native corn-starch was partially digested by adsorbed amylases during the course of 12 h at 50 degrees C, with initiation of granular pitting. Further incubation of the reaction mixture resulted in considerable morphological changes in cornstarch granules, and the main soluble products were maltose, maltotriose and higher oligosaccharides.