Optimized extraction process and compositional analysis of bioflocculant produced by Klebsiella M1

Abstract

The extraction process was optimized and compositional analysis was carried out for bioflocculant produced by Klebsiella M1. Single factor and response surface tests were adopted to optimize extraction of the bioflocculant. Physical and chemical tests were performed to qualitatively and quantitatively determine the chemical components of the bioflocculant. The molecular structure was analyzed by ultraviolet spectroscopy, Fourier transform infrared spectroscopy, gas chromatography, nuclear magnetic resonance spectroscopy, gel chromatography, and scanning electron microscopy. The optimum extraction conditions for the flocculant produced from Klebsiella M1 bacteria were as follows: anhydrous ethanol as the extractant, a material to liquid ratio of 1.54:1, pH of 9.06, and an extraction time of 12 h. The flocculant yield was up to 3.91 g/L. The bioflocculant was composed mainly of polysaccharides (65.9%) and proteins (19.7%). The polysaccharide molecular weight was 4.78 × 106 D, and it was comprised of L-rhamnose, L-arabinose, L-fucose, D-xylose, D-mannose, D-glucose, and D-galactose at the ratio 0.29:0.36:1:0.31:0.47:0.57:1.01. The polysaccharide contained hydroxyl and oxygen-containing functional groups (δ = 3.5 to 4.5 ppm) and aromatic groups (δ = 7 ppm). Thus, the bioflocculant produced by M1 bacteria was a polysaccharide type and anhydrous ethanol was a suitable extractant.