Study on Preliminary Extraction and Purification of Bioflocculant Produced by Strain F2

The strain F2 which produce excellent flocculating substance were isolated from soil samples and identified as Rhizobium radiobacter. The isolates F2 produced the flocculating substance during the late logarithmic growth phase and the early stationary growth phase. It was founded that the flocculation activated substances of BF distributed mainly in upper phase and were mainly composed of polysaccharide (83.0%) and protein (17.0%). The flocculation activated substances could be recovered from the supernatant of the fermented medium by cold acetone precipitation and purified by treating with Sevag reagent. It suggested that the optimum extracting conditions were that concentrating multiple is 1/4, acetone consistency is 100%, acetone quantity is 1:2, precipitating time is 2 h, and pH is 7, the rate of extraction for the polysaccharides was 30.2%; the optimum purifying conditions were that Vsample:Vsevag is 2:3, Vchloroform:Vbutanol is 5:2, purifying time is 30 min, the rate of eliminating for the protein was 74.2%. After the preliminary extraction and purification, BF remained high flocculating activity.