Whole-Cell Biotransformation for the Preparation of Chromopyrrolic Acid and 5,5'-dichloro-Chromopyrrolic Acid in Escherichia coli.

Chromopyrrolic acid (CPA) and its congeners are important intermediates for the biosynthesis and synthesis of various dimeric tryptophan natural products. We have constructed two E. coli strains (CPA001/CPA002) harboring a single plasmid carrying genes coding for a combination of two enzymes (LaStaO/LzrO and VioB) that are able to convert L-tryptophan (L-Trp)/5-chloro-L-tryotophan (5-Cl-L-Trp) to chromopyrrolic acid (CPA)/5,5'-dichloro-chromopyrrolic acid (5,5'-diCl-CPA). Effect on the production of CPA were evaluated by varying the parameters of strain cultivation and biotransformation process. Under the optimized conditions, up to 325 mg/L of CPA and 275 mg/L of 5,5'-diCl-CPA could be obtained by supplementing L-Trp and 5-Cl-L-Trp, respectively, to a working culture of CPA001, or to a phosphate buffer-resuspended culture of CPA002. The practicability of this whole-cell biotransformation system could also be served as a potential platform for the preparation of CPA congeners.