Study On The Flocculating Activity And Mechanisms Of Soluble Soybean Polysaccharides

Soluble soybean polysaccharides (SSPS P₁,SSPS P₂,SSPS P₃) were extracted under neutral, alkaline and acid condition,respectively. In this paper, the flocculating activities and mechnisms of SSPSs in kaolin, yeast and protein suspention were studied. The following results were achieved:(1)The flocculation activities of SSPSs was influenced by addition of cations to suspensions. In kaolin suspension, the cation's effect decreased in the order of trivalent, bivalent and monovalent. Al³⁺, Fe³⁺, Fe²⁺, Mg²⁺, Ca²⁺, K⁺, Na⁺ all could stimulate the flocculating activities of SSPS P₁ and SSPS P₂ in yeast suspention. The flocculating activity of SSPS P₂ could not be stimulated by Mg²⁺ and K⁺. In protein suspention, trivalent and bivalent cations could stimulate the flocculating activity of three SSPSs and Monovalent cations could not. The flocculating activity of SSPSs were best stumulated by the addition of Fe³⁺.(2)Combined with Fe³⁺, the flocculating activity of three SSPSs in kaolin suspention decreased in the order of SSPS P₂, SSPS P₃, SSPS P₁.The effects of SSPS P₂ concentration, Fe³⁺ concentration, temperature and pH on flocculating activity were investigated and optimized by using Box–Behnken Design (BBD). In this research, Fe³⁺ concentration and pH exhibited significant effects on flocculating activity. There was significant interaction between Fe³⁺ concentration and pH. From the 3D response surface graph, maximum flocculating activity was in the condition of SSPS P₂ concentration 0.99 mg/l, Fe³⁺ concentration 0.04 mmol/l, pH 6.67 and temperature 43℃.The rate could reach 97.30% in this condition.(3)Combined with Fe³⁺, the flocculating activity of three SSPSs in yeast suspention decreased in the order of SSPS P₁, SSPS P₂, SSPS P 3 . The effects of SSPS P₁ concentration, Fe³⁺ concentration, temperature and pH on flocculating activity were investigated and optimized by using Box–Behnken Design (BBD). In this research, SSPS P₁ concentration, pH and temperature exhibited significant effects on flocculating activity. There was significant interaction between SSPS P₁ concentration and pH. From the 3D response surface graph, maximum flocculating activity were in the condition of SSPS P₂ concentration 11.62mg/L, Fe³⁺ concentration 0.27 mmol/l, pH 8.79 and temperature 28.48℃.The rate could reach 62.01% in this condition.(4)Combined with Fe³⁺, the flocculating activity of three SSPSs in protein suspention decreased in the order of SSPS P₁, SSPS P₃, SSPS P₂. The effect of SSPS P₁ concentration, Fe³⁺ concentration, temperature and pH on flocculating activity was investigated and optimized by using Box–Behnken Design (BBD). Results also showed that there were significant interactions between Fe³⁺ concentration and pH , between Fe³⁺ concentration and temperature. From the 3D response surface graph, maximum flocculating activity was in the condition of SSPS P₂ concentration 1.65mg/l, Fe³⁺ concentration 0.87 mmol/l, pH 7.91 and temperature 40.27℃. The rate could reach 79.92% in this condition.(5)The flocculation mechanisms of SSPS were as follows: SSPS had a role in bridging adsorption, while elements of the network structure as a result of both the role of net fishing. Fe³⁺ outsided the suface of suspended particles can compress the electric double layer and charge. It also can bridge so that collodal particle combine to form larger particles from the rapid settlement to promote flocculation.