Abstract: Before and after the treatment of high pressures ranged from 40~160 MPa, the p hysiological and biochemical characters and the flocculating activity of the metabolites of bioflocculantproducing compound bacterium were investigated. The results suggest that high pressures partly impacted the physiological and biochemical characters but had significant effects on the morphology. Furthermore the flocculating activity of bacterium No.2 had an obvious threshold of pressure, its ratio of flocculation was 60.9% at 70 MPa, but that of bioflocculantproducing compound bacterium changed little. The ratios of flocculation were all above 95% under various pressures.

Key words: high pressure, compound bacterium, flocculating activity