Purification and characterization of agarase from Rhodococcus sp. Q5, a novel agarolytic bacterium isolated from printing and dyeing wastewater

An extracellular agarase was purified from Rhodococcus sp. Q5, a novel agar-degrading bacterium isolated from printing and dyeing wastewater. Agarase staining of the purified agarase on an SDS-polyacrylamide gel revealed a single band with an apparent molecular weight of 54 kDa. The optimum pH and temperature of agarase were 6.0 and 40 °C, respectively. The activity of the agarase was stable at low temperatures, and more than 90% activity was retained until 40 °C. It was stable in the pH range from pH 5.0 to 8.0, and more than 87% of the residual activity was retained. No significant activation or inhibition of the agarase was observed in the presence of Na+, K+ or Ca2 +; whereas, Ag+, Ba2 +, Pb2 +, Sn2 +, Zn2 +, Fe3 +, Mg2 +, Fe2 +, SDS, and EDTA inhibited the enzyme activity. This agarase gave Km and Vmax values of 1.47 mg ml− 1 and 0.98 μM min− 1 ml− 1. The components of the hydrolytic product analyzed by the linear ion trap mass spectrometry showed that agarase mainly produced trisaccharide, as well as a small amount of disaccharides, tetrose, pentasaccharide, and hexose.

► An agarase (54 kDa) was purified from Rhodococcus sp. Q5.
► Effects of temperature and pH on agarase activity and stability were studied.
► Heavy metal ions, SDS, and EDTA inhibited the enzyme activity.
► This agarase gave Km and Vmax values of 1.47 mg ml− 1 and 0.98 μM min− 1 ml− 1.
► The agarase mainly produced trisaccharide.