Effective removal of Cryptosporidium by a novel bioflocculant.

Extracellular biopolymer produced from Klebsiella terrigena was found to have excellent flocculating ability over a wide range of colloid particles (0.5 to 25micro). The biopolymer was thermostable, with an optimum temperature for flocculation of 30 degrees C. Analysis with Fourier transform infrared spectrophotometry (FT-IR) shows that the biopolymer mainly possesses hydroxyl, carboxyl, and methoxyl groups, with neutral sugar and uronic acid as its major and minor components, and the structure of a polysaccharide. The average molecular weight of the biopolymer was greater than 2 x 10(3) kilodalton (KDa), as determined by gel permeation chromatography. Scanning electron microscopy indicated a porous morphology of the biopolymer. At a dosage of 2 mg/L, the purified biopolymer could remove 62.3% of Cryptosporidium oocysts (1 x 10(6)) spiked in tap water samples. Calcium (5mM) was required for effective removal. The removal efficiency of Cryptosporidium oocysts by the biopolymer remained unaltered over a pH range of 6 to 8. The results of this study indicates a possible utility of the Klebsiella terrigena biopolymer as an alternative to typically used chemical flocculants for removal of Cryptosporidium oocysts from water.