Increased β‐Carotene Production in Recombinant Escherichia coli Harboring an Engineered Isoprenoid Precursor Pathway with Mevalonate Addition

When pT‐LYCm4 containing lycopene synthetic genes was co‐transformed with pSUcrtY or pSHcrtY containing crtY gene of Pantoea ananatis (P. ananatis) or Pantoea agglomerans (P.agglomerans), β‐carotene productions of 36 and 35 mg/L were obtained, respectively. No lycopene was detected in the β‐carotene production culture. pT‐HB, constructed by addition of P. ananatis crtY gene into pT‐LYCm4, was used for co‐transformation with pSdxs and pSSN12Didi, which increased isopentenyl diphosphate and dimethylallyl diphosphate synthesis. β‐Carotene production significantly increased 1.5‐fold (51 mg/L) with the amplification of the dxs gene through pSdxs and 4‐fold (135 mg/L) with the mevalonate bottom pathway of pSSN12Didi in the presence of 3.3 mM mevalonate. The pT‐DHB, constructed by integrating the dxs gene into pT‐HB, was used for cotransformation of Escherichia coli (E. coli) harboring pSSN12Didi, resulting in β‐carotene production of 141 mg/L. Recombinant E. coli harboring pT‐DHB and pSSN12Didi was used to maximize β‐carotene production by adjusting the available amounts of glycerol, a carbon source, and mevalonate, the precursor of the mevalonate bottom pathway. When recombinant E. coli was given 16.5 mM mevalonate and 2.5% (w/v) glycerol, β‐carotene production of 503 mg/L in concentration and 49.3 mg/g DCW in content was obtained at 144 h, which was the highest level of carotenoid production in E. coli ever reported in the literature.