[Mechanism of Cr(VI) biosorption by flocculating yeast]

The flocculating yeast strain SPSC01 is a fusant strain of Saccharomyces cerevisiae and Schizosaccharomyces pombe. The use of SPSC01 to absorb Cr(VI) from Cr(VI) containing aqueous solution would greatly reduce the cost of post-adsorption separation, since the superior flocculating property of SPSC01 would allow easy separation of the Cr(VI)-biomass from the solution. In order to investigate the effects of flocculating proteins on Cr(VI) reduction and absorption by SPSC01, the absorption behaviors of SPSC01 and its parental strains were compared. The results showed that Cr(VI) removal rate of SPSC01 was almost the same as that of S. pombe, which also has flocculating ability, but was faster than that of S. cerevisiae, which has no flocculating ability. When the system reached equilibrium, the amount of total Cr adsorbed by S. pombe, SPSC01 and S. cerevisiae were 68.8%, 48.6% and 37.5%, respectively. This showed that flocculation was beneficial to Cr(VI) reduction and adsorption, and suggested that focculating proteins may play a role in enhancing the Cr(VI) adsorption capacity of SPSC01 and S. pombe. We investigated the mechanism of Cr(VI) adsorption by SPSC01 using chemical modification and FTIR. The results indicated that the major functional groups (amino, carboxyl and amide) of surface proteins may contribute to the absorption of Cr(VI).