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

Abstract

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 54kDa. 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 pH5.0 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 1.47mgml−1 and 0.98μMmin−1ml−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.