Figure 4. HPLC analysis and positive-ion APCI-MS spectra of the carotenoids accumulated in E. coli for the functional identification of crtZ (Detected at 452 nm).

(A) E. coli containing pACCAR16ΔcrtX and pUC19. (B) E. coli containing pACCAR16ΔcrtX and pUcrtZ. Peak 1, zeaxanthin ([M+H]⁺ at m/z = 569.4257, and [M+H-H₂O]⁺ at m/z = 551.4155). Peak 3, β-carotene ([M+H]⁺ at m/z = 537.4405).