Molecular cloning, purification, expression, and characterization of β-1, 4-endoglucanase gene (Cel5A) from Eubacterium cellulosolvens sp. isolated from Holstein steers’ rumen

OBJECTIVE: This study was conducted to isolate the cellulolytic microorganism from the rumen of Holstein steers and characterize endoglucanase gene (Cel5A) from the isolated microorganism. METHODS: To isolate anaerobic microbes having endoglucanase, rumen fluid was obtained from Holstein steers fed roughage diet. The isolated anaerobic bacteria had 98% similarity with Eubacterium cellulosolvens (E. cellulosolvens) Ce2 (Accession number: AB163733). The Cel5A from isolated E. cellulolsovens sp. was cloned using the published genome sequence and expressed through the Escherichia coli BL21. RESULTS: The maximum activity of recombinant Cel5A (rCel5A) was observed at 50°C and pH 4.0. The enzyme was constant at the temperature range of 20°C to 40°C but also, at the pH range of 3 to 9. The metal ions including Ca(2+), K(+), Ni(2+), Mg(2+), and Fe(2+) increased the endoglucanase activity but the addition of Mn(2+), Cu(2+), and Zn(2+) decreased. The Km and Vmax value of rCel5A were 14.05 mg/mL and 45.66 μmol/min/mg. Turnover number, Kcat and catalytic efficiency, Kcat/Km values of rCel5A was 96.69 (s(−1)) and 6.88 (mL/mg/s), respectively. CONCLUSION: Our results indicated that rCel5A of E. cellulosolvens isolated from Holstein steers had a broad pH range with high stability under various conditions, which might be one of the beneficial characteristics of this enzyme for possible industrial application.