Optimized production and characterization of cation-independent bioflocculant produced by Klebsiella sp. 59L
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RESEARCH ARTICLE
Optimized production and characterization of cation-independent bioflocculant produced by Klebsiella sp. 59L Keyu Fang 1 & Boji Wang 1 & Yao Zhang 1 & Hongjing Li 1 Received: 24 February 2020 / Accepted: 6 October 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The cation-independent bioflocculant (59LF) extracted from Klebsiella sp. 59L was characterized. 59LF consisted of protein (4.8%) and total sugar (85.2%) with high molecular weight (93.82% of 2120 kDa), and total sugar was composed of 76.45% of neutral sugar, 3.65% of uronic acid, and 1.43% of amino sugar. Results indicated that 59LF was pH tolerant and thermally stable, and the maximum yield of 59LF was 4.078 g/L after 48 h culture. The optimal flocculating activity for Kaolin particles was obtained when the dosage of 59LF was 7.0 mg/L without additional metal ions as coagulant aids. Furthermore, the surface properties of 59LF were observed using a Fourier-transform infrared spectrophotometer and X-ray photoelectron spectroscopy, whereas a porous structure was detected by a scanning electron microscope. Thus, a primary flocculation mechanism of 59LF was proposed. This study provided a potential cation-independent bioflocculant with high productivity and low dosage in future application. Keywords Bioflocculant 59LF . High productivity . Low dosage . pH tolerant . Flocculating activity . Flocculation mechanism
Introduction Flocculation has a significant effect on removing contaminants and poisonous suspended particles in wastewater (Li et al. 2014). In general, flocculants are composed of three categories: inorganic flocculants (alum, multivalent metal salts, etc.), organic flocculants (e.g., cationic, anionic, and amphoteric polyacrylamide), and naturally occurring flocculants (such as starch and bioflocculant) (Xia et al. 2008). Based on previous reports, the extensive use of inorganic and organic flocculating agents could increase the risk of environmental pollution (Lofrano et al. 2013; Blanco et al. 2010; Zhang et al. 2013). Accordingly, the eco-friendly, naturally
Responsible Editor: Ta Yeong Wu Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11356-020-11162-8) contains supplementary material, which is available to authorized users. * Hongjing Li [email protected] 1
Department of Environmental Science and Engineering, Fudan University, 220 Handan Road, Shanghai 200433, China
occurring flocculants have been attracting increasing attention. One of the important naturally occurring flocculants is bioflocculant with high molecular weight substances (Salehizadeh and Shojaosadati 2001; Shahadat et al. 2017), which is generated during cell growth (Li et al. 2013; Poorni and Natarajan. 2014). In previous studies, Bacillus sp. isolated from soil samples (Elkady et al. 2011), Methylobacterium sp. obtained from river water (Rahman et al. 2016), and Proteus mirabilis TJ-1 achieved from waste-activated sludge (Zhang et al. 2010) could produce bioflocculants. In gen
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