Production and characterization of high efficiency bioflocculant isolated from Klebsiella sp. ZZ-3

•The high efficient bioflocculant was produced by isolated Klebsiella sp. ZZ-3.•The bioflocculant is pH tolerant and thermal stable.•The bioflocculant is a β-type heteropolysaccharide containing some protein.•High molecular weight and multi-functional groups contributed to the flocculation.•Bridging is the main flocculation mechanism of ZZ-3. In this study, a new bioflocculant (ZZ-3) is isolated and evaluated. This novel flocculant was derived Klebsiella, which was identified by 16S rDNA sequencing as well as biochemical and physiological analyses. The composition of ZZ-3 was found to be 84.6% polysaccharides and 6.1% protein. More specifically, the amount (moles) of the polysaccharides rhamnose, mannose, and galactose were found to be 6.48, 2.47, and 1.74 greater than glucose, respectively. Results show ZZ-3 has a relatively high molecular weight (603–1820kDa) and contains many functional groups (hydroxyl, amide, carboxyl, and methoxyl) that likely contribute to flocculation. The results of microscopic observation, zeta potential measurements, and ZZ-3 bioflocculant structure suggested that bridging was the main mechanism for flocculation with kaolin. Based on a high flocculation efficiency, thermal stability, pH tolerance and the ability to flocculate without additional cations, ZZ-3 shows potential for industrial application.