Biochemical characterization of a truncated β-agarase from Microbulbifer sp. suitable for efficient production of neoagarotetraose

A truncated beta-agarase gene without the Carbohydrate-binding Modules (Aga16A-Delta CBM) from a marine bacterium Microbulbifer sp. BH-1 was cloned and successfully expressed in Escherichia coli. It encoded 279 amino acid (aa) with a predicted molecular mass of 42.1 kDa. The recombinant beta-agarase (Aga16A-Delta CBM) showed the highest sequence identity of 49% with the glycoside hydrolase (GH) family 16 beta-agarases AgaA and AgaB from Zobellia galactanivorans. Aga16A-Delta CBM showed optimal activity at 55 degrees C and pH 8.0, respectively. It was stable within the pH range of 5.0-9.5 and up to 50 degrees C. K-m and V-max values of Aga16A-Delta CBM for agarose were 1.32 mg ml(-1) and 860.9 mu mol min(-1) mg(-1), respectively. In additional, agarose was hydrolyzed by Aga16A-Delta CBM to produce 18.4 mg mL(-1) neoagarotetraose with the high yield of 93.2% (w/w). These desirable properties of Aga16A-Delta CBM may make it attractive in neoagarotetraose production.