Production and characterization of β-cyclodextrin glucanotransferase from Bacillus sp. ND1

A potent β-CGTase producing bacterium ND1 has been isolated from sugarcane field soil in India. The biochemical, physiologicaland phylogenetic analyses based on 16S rRNA gene suggest that the isolate belongs to Bacillus cereus group. The enzyme β-CGTase produced from isolate ND1 catalyzes production of β-cyclodextrin utilizing starch as a substrate which has diverse applications in various fields. The enzyme production parameters pH, temperature, and substrate concentration were optimized using Central Composite Design (CCD) of Response Surface Methodology (RSM) and were found to be 8.9, 30.55 °C, and 1.88%, respectively for optimal enzyme activity. The crude enzyme was partially purified (29-fold) using ammonium sulphate precipitation followed by ion exchange chromatography. The specific activity of the purified enzyme was found to be 63.53 U mg^-1 . The enzyme is monomeric in nature with a molecular weight of 97.4 kD as determined by SDS-PAGE. It is stable in a wide range of pH (6-10) and temperature (40-60 °C) values. The maximum CGTase activity was observed at pH 9 and temperature 50 °C. The K_m value was found to be 2.613 ± 0.5 and V_max was 0.309 ± 0.05 µg min^-1 indicating high substrate specificity. Together; these results suggest that the enzyme may be of wide commercial value in various industrial processes.