A novel beta-glucosidase capable of hydrolyzing indican to indigo was mined and isolated from Sinorhizobium meliloti using a systematic approach. The corresponding gene was amplified by PCR and overexpressed in the soluble fraction as an MBP fusion protein. The resulting enzyme easily purified to apparent homogeneity via a consecutive step in the affinity column. The recombinant enzyme was determined to be a monomer with a calculated molecular mass of 52 kDa and showed the maximum activity for indican at pH 7.0 and 45 degrees C. The kinetic parameters for indican, K(M) and V(max), were determined to be 0.97 mM and 355.6 mu M/min/mg protein, respectively, at pH 7.0 and 35 degrees C. Additionally, this enzyme hydrolyzed both the beta-(1-4)- and beta-(1-6)-glucosidic bonds and revealed a minor activity against alpha-D-glucosides. Furthermore, the enzyme was severely inhibited by DTT, indicating a possibility that the oxidation of amino acids could play a crucial role in the activity of the enzyme. (C) 2010 Elsevier Ltd. All rights reserved.