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Cyclodextrin glucanotransferase, produced by Bacillus megaterium, was characterized, and the biochemical properties of the purified enzyme were determined. The substrate specificity of the enzyme was tested with different alpha-1,4-glucans. Cyclodextrin glucanotransferase displayed maximum activity in the case of soluble starch, with a Km value of 3.4 g/L. The optimal pH and temperature values for the cyclization reaction were 7.2 and 60 degrees C, respectively. The enzyme was stable at pH 6.0-10.5 and 30 degrees C. The enzyme activity was activated by Sr2+, Mg2+, Co2+, Mn2+, and Cu2+, and it was inhibited by Zn2+ and Ag+. The molecular mass of cyclodextrin glucanotransferase was established to be 73,400 Da by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, 68,200 Da by gel chromatography, and 75,000 Da by mass spectrometry. The monomer form of the enzyme was confirmed by the analysis of the N-terminal amino acid sequence. Cyclodextrin glucanotransferase formed all three types of cyclodextrins, but the predominant product was beta-cyclodextrin.

Various kinds of substrates were tested for cyclodextrin production with cyclodextrin glucanotransferase (CGTase) from Bacillus megaterium. The enzyme formed cyclodextrin from different kinds of starch, dextrins, amylose, and amylopectin. However, the highest degree of conversion was obtained from starch. Corn starch appeared to be the best substrate -the cyclodextrin yield was 50.9%. The effect of molecular mass and preliminary treatment of starch with a-amylase on the CD yield was investigated. It was proved that CGTase preferred native starch with high molecular mass and low dextrose equivalent. The preliminary treatment with aamylase occurred to be inefficient and unnecessary since it did not lead to an increase in the CD yield. Some of the substrates were treated with pullulanase. The effect of debranching was highest in the case of corn starch: the cyclodextrin yield increased by 10%.

An extracellular multiple form of endoxylanase was isolated from the xylanolytic complex of Aspergillus niger B03. Th e enzyme was purifi ed to a homogenous form using ultrafi ltration, anion exchange chromatography, and gel fi ltration. It was a nonglycosylated protein with a molecular weight of 20,000 Da as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and 21,000 Da as determined by gel fi ltration. Th e optimal pH for the enzyme action was 5.0 and the optimal temperature was 55 °C. Endoxylanase stability was signifi cantly improved in the presence of glycerol and sorbitol. Th e enzyme activity was activated by Mn 2+ and Co 2+ , and it was inhibited by Ag + , Cu 2+ , Fe 3+ , Fe 2+ , and Pb 2+ . Th e substrate specifi city and the product profi le of the enzyme suggested that it was an endoxylanase. Th e enzyme showed a synergism with another endoxylanase from Aspergillus niger B03 in xylan hydrolysis.

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