Alginate lyases degrade alginate in a beta-elimination reaction to produce oligosaccharides. Thus, alginate lyases are widely used in the food/pharmaceutical industries and are commercially valuable. In this study, four alginate lyase encoding genes were successfully cloned from Sphingomonas sp. ZHO. The expression systems of these alginate lyases were then constructed in Escherichia coli cells. The recombinant ZHO-I, ZHO-II, ZHO-III and ZHO-IV were purified from E. coli cells and were confirmed to be monomeric enzymes with molecular weights of approximately 91, 52, 67, and 113 kDa, respectively. The conditions for enzymes to have the highest specific lyase activities were 53.2 U/mg, 42 C, pH 7.0 for ZHO-1,103.9 U/mg, 47 degrees C, pH 6.5 for ZHO-II, 13.7 U/mg, 52 degrees C, pH 7.5 for ZHO-III, and 12.3 U/mg, 37 C, pH 7.0 for ZHOIV, respectively. These recombinant enzymes were stable over a pH range. Moreover, the enzymes were active in the absence of salt ions, and their activities were substantially reduced by the addition of HgCl2. ZHO-1, ZHO-II and ZHO-HI belong to endotype alginate lyases, while ZHO-IV is an exotype alginate lyase. All types could degrade both poly-13-omannuronate and poly-oc-L-guluronate blocks, yielding alginate oligosaccharides as the main product. The Km and Vmax values were 0.51 mg/ml and 56.18 U/m1 for ZHO-1, 0.47 mg/ml and 27.5 U/ml for ZHO-II, 0.55 mg/ml and 60.24 U/ml for ZHO-Ill, and 0.41 mg/ml and 5.53 U/m1 for ZHO-IV, respectively. These features indicate that these alginate lyases are promising candidates for producing antioxidants from alginates in industrial applications. (C) 2018, The Society for Biotechnology, Japan. All rights reserved.