Screening Of A Bioflocculant-Producing Strain And Its Flocculating Characteristics

A bacterial strain was screened out from the sewage farm of Hohhot. Theoptimal cultivation conditions showed that the carbon source was sucrose, thenitrogen source was carbamide, low C/N ratio (C/N=2.5) was beneficial to microbialflocculant production, the desirable cultivation time was 84 hours, culturaltemperature was 30℃, the initial pH value was 6.0, 60ml culture medium in 150mltotal volume of triangular flask (in the case of 200r/min). According to the orthogonalexperiment, the optimum proportions of component of medium was obtained,which were sucrose 10g, yeast extract 1.3g, carbamide 0.5g, (NH₄)₂SO₄ 0.2g,KH₂PO₄ 2g, K₂HPO₄ 5g, NaCL 0.1g, Mg₂SO₄ 0.1g, H₂O 1L, pH=6.0. Flocculationtests conducted by the fermenting solution showed that the cultivation solution had agood flocculation effect on kaolin clay suspension, and the flocculation rate reaches95% in the best condition. The test of distribution of flocculating activity showed thatthe supernatant of centrifugation did not have any flocculating activity, all theflocculating activity existed in the deposit of centrifugation. The best flocculatingconditions had got from experiments of the effect of different pH, the dosage offlocculant, the kind of ion, the dosage of CaCl₂ and etc. The application of decoloringtests showed that the bioflocculant had a good decoloring effect on the wastewater ofdying. It was identified as Klebsiella sp. G by sequencing of 16S rRNA, and it is the first time to be reported that Klebsiella sp. G can produce bio-flocculant.