title: Purification and properties of a new thermostable cyclodextrin glucanotransferase from Bacillus pseudalcaliphilus 8SB.
abstract: A new cyclodextrin glucanotransferase (CGTase, EC 2.4.1.19) from an alkaliphilic halotolerant Bacillus pseudalcaliphilus 8SB was studied in respect to its γ-cyclizing activity. An efficient conversion of a raw corn starch into only two types of cyclodextrins (β- and γ-CD) was achieved by the purified enzyme. Crude enzyme obtained by ultrafiltration was purified up to fivefold by starch adsorption with a recovery of 62% activity. The enzyme was a monomer with a molecular mass 71 kDa estimated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and native PAGE. The CGTase exhibited two pH optima, at pH 6.0 and 8.0, and was at most active at 60 °C and pH 8.0. The enzyme retained more than 80% of its initial activity in a wide pH range, from 5.0 to 11.0. The CGTase was strongly inhibited by 15 mM Cu(2+), Fe(2+), Ag(+), and Zn(2+), while some metal ions, such as Ca(2+), Na(+), K(+), and Mo(7+), exerted a stimulating effect in concentration of 5 mM. The important feature of the studied CGTase was its high thermal stability: the enzyme retained almost 100% of its initial activity after 2 h of heating at 40-60 °C; its half-life was 2 h at 70 °C in the presence of 5 mM Ca(2+). The achieved 50.7% conversion of raw corn starch into 81.6% β- and 18.4% γ-CDs after 24 h enzyme reaction at 60 °C and pH 8.0 makes B. pseudalcaliphilus 8SB CGTase industrially important enzyme for cyclodextrin production.
authors: Department of Extremophilic Bacteria, Institute of Microbiology, Bulgarian Academy of Sciences, Sofia, Bulgaria.
authors: Tsvetina
authors: T
authors: Kitayska
authors: Penka
authors: P
authors: Petrova
authors: Viara
authors: V
authors: Ivanova
authors: Alexandra Ivanova
authors: AI
authors: Tonkova
mesh_terms: D001407:Bacillus / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D003505:Cyclodextrins / Q000378:metabolism; D004795:Enzyme Stability; D005964:Glucosyltransferases / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008969:Molecular Sequence Data; D012988:Soil Microbiology; D013379:Substrate Specificity; D013696:Temperature
chemical_list: D001426:Bacterial Proteins; D003505:Cyclodextrins; D005964:Glucosyltransferases; C019963:cyclomaltodextrin glucanotransferase