Design of an Escherichia coli strain to be used as platform for de novo production of flavonoid-derived compounds

Abstract

Flavonoids is a class of polyphenols with at least 9000 compounds with a wide range of medical and industrial applications. These compounds are hard to chemically synthesize and their extraction from plants is difficult, expensive and renders non-pure compounds. For this reason, the heterologous production of flavonoids using microbes and cheap carbon sources has emerged as a possible solution. Naringenin chalcone (NC) is considered the branching point of the flavonoids pathway to produce more complex compounds, namely prenylflavonoids, isoflavonoids, flavones, and flavonols. To produce NC, tyrosine is converted into coumaric acid (CA) by tyrosine ammonia-lyase (TAL). Then, CA is converted into coumaroyl-CoA by 4-coumarate-CoA ligase (4CL) that is further converted into NC by chalcone synthase (CHS). Herein, we designed and validated an efficient E. coli strain to produce NC de novo. Firstly, 2 TAL genes from different organisms were expressed in E. coli BL21, K12 MG1655 and M-PAR-121 to select the best enzyme and strain to produce CA. The highest CA production (2.54 g/L) was achieved in the tyrosine-overproducing E. coli M-PAR-121 strain expressing TAL from Flavobacterium johnsoniae (FjTAL). Then, 4 different 4CL and 3 different CHS encoding genes were selected and expressed in combination with FjTAL originating 12 different E. coli strains. The highest production of NC was achieved in the E. coli M-PAR-121 strain expressing FjTAL, At4CL and CmCHS (311.0 mg/L). In the future, this strain will be used as a platform to produce more complex compounds, namely prenylflavonoids.