Bacillus sphaericus ATCC 7055 produced an intracellular cyclodextrinase (EC 3.2.1.54). It was purified by solublilising with Triton X-100, Q-Sepharose ion-exchange chromatography, phenyl-Sepharose CL-4B hydrophobic interaction chromatography and Su perose-12 gel filtration and gave a single band on SDS-PAGE and preparative isoelectric focusing. The maxima for pH and temperature of the purified enzyme were pH 6.0-6.5 and 40 degrees C. The enzyme had a relative molecular mass of 91200-95000 and an isoelectric point of 5.3. The amino-linked pseudotetrasaccharide, acarbose, inhibited activity. As well as cyclodextrins the enzyme was active on a broad range of substrates ranging in size from maltooligosaccharides (G3) to polysaccharides such as starch and pullulan, and branched cyclodextrins. End-product profiles of the cyclodextrinase on various substrates revealed that, upon hydrolysis of 1% (w/v) alpha-, beta- and gamma-cyclodextrin and maltoheptaose, glucose and maltose were the dominant end-products. Pullulan degradation resulted in panose (92%, w/v) as the main end-product, and glucose (27%, w/v) and maltose (37%, w/v) were the sole products formed from starch degradation.