Bacillus agaradhaerens LS-3C cyclodextrin glycosyltransferase: activity and stability features

Activity and stability characteristics of an alkaline active cyclodextrin glycosyltransferase (CGTase) enzyme from the alkaliphilic Bacillus agaradhaerens LS-3C strain are reported. The enzyme displays unusually high amylolytic activity in relation to the cyclization activity. Disproportionation activity of the CGTase was optimal with maltose as the acceptor substrate. The product of cyclization reaction was predominantly β-cyclodextrin (CD) along with α-CD as a minor product, however, the CDs profile was influenced by the reaction conditions. At pH 10, α-CD was replaced by γ-CD formation. Cyclization reaction and β-CD formation were significantly promoted in the presence of CaCl2. The salt allowed the cyclization reaction to be performed at higher temperature. Increase in CDs production was also seen in the presence of 1 M sorbitol and 10% (w/v) PEG 3000, respectively. The enzyme stability was greatly enhanced with sorbitol, while alcohols had a highly negative effect on enzyme stability and hence on CDs production. β-CD and maltose brought about significant inhibition of the cyclization reaction.