Flocculation characteristics and mechanism of flocculant PCF-1767 produced by Phanerochaete chrysosporium BKMF-1767

Abstract:

[Background] The use of traditional flocculants poses security and environmental problem, while microbial flocculants have the advantages of non-toxic, no secondary pollution and easy biodegradation. Therefore, it is of great significance to find efficient and economical microbial flocculants. [Objective] To study the flocculation characteristics and mechanism of PCF-1767, an extracellular polysaccharide flocculant produced by Phanerochaete chrysosporium BKMF-1767. [Methods] The flocculating activity of the PCF-1767 was determined using a Kaolin suspension. The effects of flocculant acquisition time, flocculant dosage, pH, Ca2+ concentration and temperature on the flocculation efficiency were studied, as well as the thermal stability of PCF-1767. Flocculation mechanism of PCF-1767 was discussed from the monosaccharide composition and glycoside bond connection type, the molecular weight of polysaccharides, Zeta potential determination, and flocs morphology observation. [Results] The PCF-1767 obtained at 6–12 d displayed high flocculating activity. For higher flocculation activity of the PCF-1767 obtained at 7 d, at least 2 mmol/L Ca2+ should be added as coagulant. The optimal flocculant dosage was 0.75–1.35 mg/L, with an optimum pH range of 3.0–9.0. The flocculating activity decreased when the water temperature was higher than 50 °C. The flocculation activity of PCF-1767 was almost unchanged after 3 h water bath treatment. The primary structure of the polysaccharide in PCF-1767 obtained in different periods was similar, mainly connected by glucose in the manner of →4)Glup(1→. The molecular weight of PCF-1767 increased with the culture time, at the range of 9.897×105–2.126×106 Da. Zeta potential determination and flocs image analysis showed that the main flocculation mechanism was adsorption bridging flocculation and sweeping, instead of charge neutralization. [Conclusion] The flocculant PCF-1767 produced by P. chrysosporium BKMF-1767 has high flocculation efficiency with low dosage, wide application range and good thermal stability. In brief, PCF-1767 has good application prospects.

Key words:Microbial flocculant, Extracellular polysaccharide, Phanerochaete chrysosporium, Flocculation mechanism