Expression and biochemical characterization of a novel thermostable alkaline β-1,3-1,4-glucanase (lichenase) from an alkaliphilic Bacillus lehensis G1

Abstract

New thermostable β-1,3-1,4-glucanase (lichenase) designated as Blg29 was expressed and purified from a locally isolated alkaliphilic bacteria Bacillus lehensis G1. The genome sequence of B. lehensis predicted an open reading frame of Blg29 with a deduced of 249 amino acids and a molecular weight of 28.99 kDa. The gene encoding for Blg29 was successfully amplified via PCR and subsequently expressed as a recombinant protein using the E. coli expression system. Recombinant Blg29 was produced as a soluble form and further purified via immobilized metal ion affinity chromatography (IMAC). Based on biochemical characterization, recombinant Blg29 showed optimal activity at pH9 and temperature 60 °C respectively. This enzyme was stable for more than 2 h, incubated at 50 °C, and could withstand ∼50 % of its activity at 70 °C for an hour and a half. No significant effect on Blg29 was observed when incubated with metal ions except for a small increase with ion Ca²⁺. Blg29 showed high substrate activity towards lichenan where V_m, K_m, K_cat, and k_cat/K_m values were 2040.82 μmolmin^‾1mg^‾1, 4.69 mg/mL, and 986.39 s‾¹ and 210.32 mLs^‾1mg‾¹ respectively. The high thermostability and activity make this enzyme useable for a broad prospect in industry applications.

Keywords: Alkaliphilic; Bacillus lehensis G1; Lichenase; Thermostable; β-1,3–1,4-glucanase.