Enhancement of the Cell Immobilization for the Indolyl-3-acetic Acid Production by Using the Bacterial Surface Display Technology

By using the bacterial surface display technology, the ice nucleation proteins including INaA and INaK were used as the anchored protein. The negatively charged amino acids (aspartic acid, glutamic acid) were anchored on the surface of Escherichia coli to increase the negative charge carried on the surface of cell membrane, and the modified positively charged biochar was adsorbed to enhance the function of biochar to immobilize the cells. The corn straw biochar was modified by 2 mol·L^-1 FeCl₃ to make it positively charged, and then the modified biochar was electrostatically adsorbed to the recombinant strain with the increased negative charge on the cell surface. Compared with the control strain, the adsorption rate of the recombinant strain EPA03 was increased by 31.75%. This strategy was applied to the strain that could produce IAA efficiently by using the immobilized cells. In the continuous cycle of whole-cell catalysis, the strain EPA03 could continuously react for 6 cycles, and the accumulation of IAA increased by 42.85% compared with that of the control strain.