Breeding Heavy Metal Resistant Strains And Assay Of Absorption Capacity Of Its Immobilized Cells

After Saccharomyces cerevisiae SY1 and Rhodotorula rubra RrY001 which were as original strains were monoploided,resistance level was determined to select resistant strains.A strain named SY1-1 which Cu2+ resistance level is 3mmol/L and another named RrY001-8 which Cd2+ resistance level is 1mmol/L were obstained. The two strains were lysised to rid of cell wall by snailase. During that,the optimum conditions of information and regeneration of protoplasts were reseached:0.8mol/L NaCl is as osmosium; the concentration of snailase is 1.5% to SY1-1 and 2.0% to RrY001-8; the time of lysis is one hour and 0.3%-beta mercaptoethanol is necessary. The protoplasts obtained according the conditions above were mutated with ultraviolet ray and when time is 2 and 3minutes, the positive mutative ratio is highest. Two positive strains were selected named SY1-1-4 which Cu2+ resistance level is 7mmol/L and RrY001-8-14 which Cd2+ resistance level is 3mmol/L. The genetic stability of the two mutants maintained over 90% after 50 generations. The capacity of resisting UV and 60Co, clearing ?OH free radical were compared to original strains.The results showed that lethality of the mutants to UV and 60Co reduced obviously and the capacity of SY1-1-4 of clearing ?OH free radical is 1.7 folders higher than original strain. The original strains and mutants were induced and cultured, then cells were collected by centrigution and then dried at 45℃.The cells were immobilized with 3% alginate sodium and the functions which the immobilized cells clear heavy metal ions in waste water were researched too. The conclusion can be made that the mutants have higher absorption capacity and show good industrial propect.