This study isolated a total of seven pure cultures from activated sludge that could produce bioflocculants from 1.7% v/v H2SO4 treated hydrolysates of corn stover. The most effective strain amongst the seven isolates was identified as Ochrobactrum ciceri W2. The W2 cells produced biopolymers in logarithm growth phase, peaking at 3.8 g l(-1) in productivity on 16 h. The yielded bioflocculant was primarily consisting of polysaccharides and proteins, and maintained its flocculating activity to 0.5% w/w kaolin suspensions over pH 1-10 (at 30 degrees C) and 30-100 degrees C (at pH 7). This study also revealed that the strain W2 could utilize biopolymers from hydrolysate of corn stover without addition of excess phosphate salts, which could largely reduce production costs of bioflocculants. (C) 2012 Elsevier Ltd. All rights reserved.