Effect of adaptive laboratory evolution of engineered Escherichia coli in acetate on the biosynthesis of succinic acid from glucose in two-stage cultivation.

Escherichia coli MLB (MG1655 ΔpflB ΔldhA), which can hardly grow on glucose with little succinate accumulation under anaerobic conditions. Two-stage fermentation is a fermentation in which the first stage is used for cell growth and the second stage is used for product production. The ability of glucose consumption and succinate production of MLB under anaerobic conditions can be improved significantly by using acetate as the solo carbon source under aerobic condition during the two-stage fermentation. Then, the adaptive laboratory evolution (ALE) of growing on acetate was applied here. We assumed that the activities of succinate production related enzymes might be further improved in this study. E. coli MLB46-05 evolved from MLB and it had an improved growth phenotype on acetate. Interestingly, in MLB46-05, the yield and tolerance of succinic acid in the anaerobic condition of two-stage fermentation were improved significantly. According to transcriptome analysis, upregulation of the glyoxylate cycle and the activity of stress regulatory factors are the possible reasons for the elevated yield. And the increased tolerance to acetate made it more tolerant to high concentrations of glucose and succinate. Finally, strain MLB46-05 produced 111 g/L of succinic acid with a product yield of 0.74 g/g glucose. SYNOPSIS.

Snail inhibits metastasis via regulation of E­cadherin and is associated with prognosis in colorectal cancer.

The overall survival (OS) rate of patients with colorectal cancer (CRC) remains low due to the lack of clear prognostic markers. Therefore, the identification of valuable prognostic markers is urgently required. Snail and E-Cadherin (E-Cad) are important protein molecules in the EMT process and play a crucial role in tumor invasion and metastasis. The present study investigated the clinical significance of Snail and E-cad expression in CRC. Compared with those in adjacent tissue, the expression levels of Snail and E-cad were significantly increased and decreased, respectively, in CRC. Moreover, low Snail and high E-cad expression were associated with clinicopathological features and longer OS time. Furthermore, Snail and E-cad could predict the prognosis of patients with CRC. Reverse transcription-qPCR, Western blotting, Wound scratch assay, High content cell migration experiment, which showed that low Snail or high E-cad expression inhibited invasion and metastasis of CRC. In conclusion, Snail can promote CRC invasion and metastasis by regulating E-cad. Snail and E-cad expression constitute a novel prognostic marker for CRC, and the present study revealed a greater combined effect of Snail and E-cad as effective prognostic markers in CRC for the first time.