| 摘要 |
Improved methods are provided for replication and expression of prochymosin coding gene in E. coli. Novel expression plasmids having prochymosin coding gene operatively attached to the E. coli trp operon have been developed. These plasmids have been inserted into E. coli host cells by transformation, providing new strains to E. coli with high expression capability. The techniques for preparing such expression plasmids and E. coli strains derived therefrom are described. The modified cells, under appropriate cultivation conditions, produces a substantial amount of prochymosin which on activation (viz., in the form of chymosin) displays milk-clotting activity. The genetically engineered new strains of E. coil have been deposited with the Fermentation Research Institute, Ibaragi, Japan under the Budapest Treaty. The methods are thus useful in the massive production of prochymosin by fermentation, and are superior to the known art in the field. |
