Engineering MEP pathway in Escherichia coli for amorphadiene production and optimizing the bioprocess through glucose feeding control

Abstract:

The pathway of 2-methyl-D-erythritol-4-phosphate (MEP) is the exclusive isoprenoid precursor biosynthetic pathway in Escherichia coli, with a higher theoretical yield than mevalonate (MVA) pathway. However, due to lack of information about the regulation of MEP pathway, only engineering MEP pathway in E. coli achieved limited improvement of heterologous isoprenoid production. We used exogenous MEP pathway genes to improve MEP pathway in E. coli and optimized the glucose feeding to release the potential of MEP pathway. The results demonstrate that co-expression of dxs2 from Streptomyces avermitilis and idi from Bacillus subtilis can increase amorphadiene production with 12.2-fold compared with the wild-type strain in shake flask fermentation. Then we established a high-cell density fermentation process for the engineered strain, and found that the phase from 24 to 72 h is important for product biosynthesis. The optimization of glucose feeding rate during 24 to 72 h significantly improved product accumulation, which was improved from 2.5 to 4.85 g/L, within the same process time. Considering the attenuation of strain metabolism after 72 h, this study further modulated the glucose feeding rate during exponential phase to control strain growth and the amorphadiene yield eventually reached to 6.1 g/L. These results provided useful information to develop engineered E. coli for isoprenoid production through MEP pathway engineering.