Cloning and Expression of Bacillus pumilis Bg57 β-Glucanase Gene in Pichia pastoris: Purification and Characteristics of Recombinant Enzyme

Abstract

The isolation, heterologous gene expression, and characteristics of a new β-glucanase from Bacillus pumilus is described. The bgl1 gene from the Bacillus pumilus Bg57 VKPM В-13195 strain, which consists of 729 nucleotides, encodes a secreted endo-β-l,3(4)-D-glucanase (EC 3.2.1.6) containing 214 amino acids and 28 residues of the putative signal peptide in the N-terminal area. The nucleotide sequence of bgl1 and amino acid sequence of the mature Bgl protein have the highest homology (89 and 95%, respectively) with the sequences for β-l,3-l,4-glucanase from Bacillus licheniformis. A fragment of the gene encoding the mature protein was expressed in Pichia pastoris. The purified recombinant enzyme of Bgl was active towards barley β-glucan and lichenin. With barley β-glucan, the optimal pH and temperature were shown to be 6.0 and 50°C, respectively; K_m and V_max were 2.2 mg/mL and 3036.4 μmol/(min mg), respectively. The recombinant protein Bgl showed a high specific activity, thermal stability, and resistance to digestive enzymes. Other characteristics of the recombinant protein, including pH stability and sensitivity to metal ions and chemical reagents, were also determined.