Metabolic Engineering of E. coli for Xylose Production from Glucose as the Sole Carbon Source

Abstract

Xylose is the raw material for the synthesis of many important platform compounds. At present, xylose is commercially produced by chemical extraction. However, there are still some bottlenecks in the extraction of xylose, including complicated operation processes and the chemical substances introduced, leading to the high cost of xylose and of synthesizing the downstream compounds of xylose. The current market price of xylose is 8× that of glucose, so using low-cost glucose as the substrate to produce the downstream compounds of xylose can theoretically reduce the cost by 70%. Here, we designed a pathway for the biosynthesis of xylose from glucose in Escherichia coli. This biosynthetic pathway was achieved by overexpressing five genes, namely, zwf, pgl, gnd, rpe, and xylA, while replacing the native xylulose kinase gene xylB with araL from B. subtilis, which displays phosphatase activity toward D-xylulose 5-phosphate. The yield of xylose was increased to 3.3 g/L by optimizing the metabolic pathway. Furthermore, xylitol was successfully synthesized by introducing the xyl1 gene, which suggested that the biosynthetic pathway of xylose from glucose is universally applicable for the synthesis of xylose downstream compounds. This is the first study to synthesize xylose and its downstream compounds by using glucose as a substrate, which not only reduces the cost of raw materials, but also alleviates carbon catabolite repression (CCR), providing a new idea for the synthesis of downstream compounds of xylose.

Integrating Carbohydrate and C1 Utilization for Chemicals Production

“…In addition, the production comes with low efficiency and high production cost [8a] . Besides, one major drawback which comes up for the utilization of glucose and xylose using microorganisms is catabolite repression, i. e., glucose actively represses the expression of genes for xylose transporters and xylose conversion making a co‐fermentation of glucose and xylose difficult [10] …”

“…[8a] Besides, one major drawback which comes up for the utilization of glucose and xylose using microorganisms is catabolite repression, i. e., glucose actively represses the expression of genes for xylose transporters and xylose conversion making a co-fermentation of glucose and xylose difficult. [10] Ethanol as one of the most common and widely used biofuels by now, [11] is naturally produced by many organisms like yeast or bacteria, by conversion of the central metabolite pyruvate. [12] Bioethanol production is mostly based on sugarcane production by fermentation of glucose with established hosts such as Saccharomyces cerevisiae, which use their natural utilization pathways for ethanol production.…”