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 (603–1820 kDa) 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.