An alginate lyase-producing bacterial strain, Vibrio sp. QY105, was isolated from sea mud of Qingdao. It secreted 90 % of total enzyme activity within the first 20 h of fermentation. An alginate lyase, AlyV5, with an apparent MW of 37 kDa and a specific activity of 2152 U/mg was purified from the culture supernatant. It was most active at 38 A degrees C and pH 7.0 in 20 mM Tris/HCl. The enzyme was stable over a broad pH range (6.0-9.0) and retained similar to 40 % activity after holding at 90 A degrees C for 10 min. AlyV5 showed activities towards both polyguluronate and polymannuronate, but degraded the former more efficiently. AlyV5 mainly produced disaccharide, trisaccharide and tetrasaccharide from polyguluronate, trisaccharide, tetrasaccharide and pentasaccharide from polymannuronate. The purpose of this study is to find a polyG-preference alginate lyase for the saccharification of alginate combined with our polyM-preference alginate lyases.