Batch and High Cell Density Fed-Batch Culture Productions of an Organophosphorus Hydrolase

摘要

Organophosphorus hydrolases (OPH) are of great interest to the U.S. Army for their potential use in the non-toxic, non-corrosive decontamination against VX. OPH genes had been cloned and over expressed in Escherichia coli by other researchers. However, a common problem has been that of a low expression level. In this study, batch cultures in both complex (e.g., Lauria Broth) and minimal (succinate) media as well as high cell density cultures in the succinate medium were performed to obtain a yield information for a cobolt- requiring OPH. High cell density fed-batch cultures of E. coli carrying a cloned OPH gene were achieve by a pH control with an acidic 200 g/L succinate (pH = 4 to 4.3) medium. The uptake of carbon source, succinic acid instead of succinate, by the cell cultures raised the pH of broth culture which triggered an addition of the acidic succinate medium. This also provided an additional amount of carbon source for high cell density cultures. Up to 300mg OPH/L of fermentation broth was achieved using the high cell density fed batch cultures.