Screening And Characterization Of High Efficient Copper Adsorbing Yeast Strains

After enrich culturing, 21 strains yeast were isolated from 30 Orchard soil samples collected from Chengdu, Nanchong and Yibin in Sichuan province, and their colony aspects and cellular morphology was observed. Based on the results of adsorption experiment of Cu²⁺, Y15, Y17 and Y21 were screened as high efficienct copper adsorbing strains. By using single factor and the orthogonal experiments, the concentration of glucose in YEPD liquid medium, culture temperature, growth pH and inoculation amount of tested strains was determined to dectect the optimal culture condition; moreover, type of culture medium, reaction pH, the amount of cell biomass added, adsorption time and reaction temperature was performed to obtain the the optimal reaction condition. The results were as the follows:All the 21 yeast strains had the Copper adsorbing ability, but the Copper removal ratio in the wastewater of strains Y15, Y17 and Y21 was more than 75%, hence, they were screened as high efficient Copper adsorbing strains.The result of single factor and the orthogonal experiment suggested that the optimal culture conditions for Y15 and Y21 were that the culture temperature 30℃, growth medium pH value was 4.0, the inoculation amount of tested strains was 10%, the concentration of glucose added into YEPD liquid media was 8%.The optimal culture conditions of Y17 were culture temperature was 30℃, growth medium pH value was 4.0, the inoculation amount of tested strains was 5%, the concentration of glucose in YEPD liquid media was 5%. Underr these conditions, the dry weight biomass of 3 yeast strains reached to 17.9 mg, 16.8 mg and 17.5mg per ml liquid culture.Result of single factor experiment showed that the amount of cell biomass added, type of culture medium, the reaction pH was the most dominating factor affecting strains Y15, Y17 and Y21 adsorbing Cu²⁺. The optimal absorption conditions of Y15, when cultured in sprouts juice medium, were as following: the reaction pH was 5.0, absorption time was 40 min, the amount of cell biomass was 5.0g/L. Treating at those conditions, the adsorbing rate reached to 80.3%; The optimal reaction conditions of strain Y17 were the follwing when cultured in PDA medium, reaction pH was 4.0, absorption time was 40min, cell biomassadde was 1.0g/L, at these conditions, the adsorbing achieved 81.6%. As for strain Y21 culturing in PDA medium, its optimal reaction conditions was reaction pH5.0, absorption time 40min and 1.0g/L of biomass, and the adsorbing rate was up to 79.7%.On the basis of different biochemical processing and the desorption experiment, the cell wall of Y17 was identified the main place occuring biosorption process. Group -NH₂, -COOH on the surface of the cell wall played an important role on the boisorption process.Simulating the CASS reaction pond, a laboratary reactor was designed to treat the dejecta wastewater. The growth situation when inoculted singles strain of Y15, Y17, Y21 and the mixed culture of 3 strains in the processor was determined. The result indicated that strain Y21 could grow well in the treatment system, and the activated sludge removed Cu²⁺ in the waste water efficiently, the removal rate was 92.3%. After treating, the congcentration of Cu²⁺ in the waste water measured up China national Copper discharge standards.