Preparation Of New Type Displayed Biosorbent From Saccharomyces Cerevisiae With Random Phage-displayed Peptide Library

The heavy metal cadmium pollution is a serious problem which has been puzzling the science researcher.Compared with the traditional treatment method of heavy metal pollution,the bioremediation methods curbing heavy metal pollution are more effective,convenient and save.However,only using bioremediation methods cannot satisfy the requirement of controlling the pollution of the heavy metals.so,we need to combine the biological display peptide library with the cell surface display technology to establish a new type of cell surface adsorbent.The phage display peptide library was used for the screening of metal ions specific peptide,it could be a source of infinite specific peptide.After screening the library,we could get ligand molecules having stronger affinity.The saccharomyces cerevisiae was used as the strains for research,itself is a kind of good heavy metal ions adsorption materials.The cell lectin surface engineering system of s.cerevisiae was used to make the cadmium metal peptide display on the cell surface combine specific,it could make the adsorption efficiency improved.In this study,we used the chelating resin which could combined the cadmium ion as targets molecular.The short peptide sequence having the affinity for this kind of metal ions were obtained by the specific binding screening experiment with phage 12 peptide library.The third round of screening,the P/N value reached 56.It suggested that the phage clones had the strong specificity.Four metal binding peptide is available by randomly determinating the phage sequence.Then,we transferred the PYD1 plasmid combining metal cadmium ion peptide into s.cerevisiae by the conversion method of acetic acid lithium heat shock,method is lithium acetate method.When expoiring the adsorption efficiency,we could find that the adsorption capacity of the engineering bacteria was superior to the control bacteria EBY100 with joining the same quality of cadmium,and inserted into of the s.cerevisiae had the strongest adsorption capacity,it could reach 35%,when the sequence 3 was inserted to s.cerevisiae.When the recombinant bacteria was immobilized by the sodium alginate we found that the immobilized particle was easy to shape and had certain mechanical strength and the efficiency of biological adsorbent also was improved.In the research process of immobilized condition,we found the optimal conditions where the calcium chloride concentration was 2%,the sodium alginate concentration was 3%,the temperature was 25?.Under the optimal conditions,the adsorption performance of immobilized bacteria was best.When studing the adsorption performance of immobilized bacteria,we found the adsorption efficiency of recombinant strains had great improvement than the control strain,it could reach 55.7%.