Characterization of a bioflocculant produced by the marine myxobacterium Nannocystis sp. NU-2

• DOI: 10.1007/s00253-002-1023-7
• Publication Date: 2003-02-13T02:43:30Z
• Authors: Zhang J.; Liu Z.; Wang S.; Jiang P.
• Keywords: Rhodamines; Molecular Sequence Data; Polysaccharides, Bacterial; Flocculation; Sequence Analysis, DNA; DNA, Ribosomal; 01 natural sciences; 6. Clean water; Bacterial Proteins; RNA, Ribosomal, 16S; Seawater; Myxococcales; Phylogeny; Biotechnology; Fluorescent Dyes; 0105 earth and related environmental sciences

The marine myxobacterium strain NU-2, which can grow on high concentrations (up to 7%) of NaCl, was isolated from a salt soil sample collected from the coast of the Huanghai Sea, China. Morphological properties and 16S rDNA sequence analysis indicated that the isolate is a novel species related to the genus Nannocystis. Nannocystis sp. NU-2 produced a new kind of flocculating substance in a starch medium with a yield of 14.8 g l(-1). The NU-2 flocculant was composed of 40.3% proteins and 56.5% polysaccharides, of which glucose, mannose and glucuronic acid were the principal constituents in the relative proportions of 5:4:1. The flocculation activity of the NU-2 flocculant depends strongly on cations such as Fe(3+) and Al(3+). When a 30 mg l(-1) FeCl(3) solution is present in kaolin clay suspension, 30 mg l(-1)of the flocculant produced a high flocculating activity value of 90%, which remained unchanged over an extensive pH range (pH 2.0-13.0). The flocculant was tested for its ability to bleach dyeing liquors, and the bleaching activities were 98.2% for acid red in 100 mg l(-1)of the flocculant and 99.0% for direct emerald blue in 50 mg l(-1)of the flocculant under test conditions. Use of the flocculant to bleach basic pink and cation emerald blue liquors was not effective.