Studies On Enhancing Lycopene Production By Fructose In Crtebi Recombinant Escherichia Coli

Lycopene is a kind of significant carotenoids which has beneficial biological and pharmaceutical activities, including anti-cancer, anti-inflammatory, and anti-oxidative activities. Consequently, lycopene is widely used as a supplement in functional foods, animal feed, nutraceuticals, and pharmaceuticals and as an additive in cosmetics. In recent years, with concerns about the side effects of synthetic chemicals and increasingly advocating of natural products, researchers gradually paid much attention to produce lycopene by microbe fermentation.In order to achieve high-level production of lycopene in E. coli, in this work, we successfully constructed four crtEBI recombinant E. coli strains by using E. coli DH5α, BL21(DE3), K-12, JM109as the host strains. The results showed that the lycopene yield reach the highest level when E. coli K-12was selected as the host strains. On this basis, we analyzed the cell mass and the lycopene production of E. coli K-12(crtEBI) in various conditions and finally confirmed that culture conditions of E. coli K-12(crtEBI). In addition, according to the previous reports, dxs gene was cloned using PCR and the recombinant plasmid pET28a-dxs containing dxs gene was constructed to modify the metabolic pathway of lycopene in E. coli K-12(crtEBI). However, it exhibited little increase on the lycopene yield. Furthermore, it was testifyed that lycopene yield was significantly increased by adding6g/L fructose into LB medium when various carbon sources, nitrogen sources and TCA intermediates was supplemented into the medium to change the lycopene production in E. coli K-12(crtEBI). Besides, the growth curve of E. coli K-12(crtEBI) and the yield curve of lycopene illustrate as a additional carbon, we demonstrated that fructose rather than glucose is more effective auxillary source to enhance lycopene producion by analyzing the growth curve and the lycopene yield curve. As a result,we were able to reach a finally lycopene yield up to1800mg/L for24h in a5L fermenter with recombinant E. coli k-12(crtEBI). In the end, the results of RT-PCR demonstrated that fructose could stimulate the intermediates metabolic process mediated by PEP and Pyr by promoting the transcription of FruA, FruK, Pck and inhibiting the transcription of Ppc, indicating that the transcriptional regulation might play important roles in the induction of fructose on the production of lycopene.