Conversion of glucose‐xylose mixtures to pyruvate using a consortium of metabolically engineered Escherichia coli

Abstract

Two strains of Escherichia coli were engineered to accumulate pyruvic acid from two sugars found in lignocellulosic hydrolysates by knockouts in the aceE, ppsA, poxB, and ldhA genes. Additionally, since glucose and xylose are typically consumed sequentially due to carbon catabolite repression in E. coli, one strain (MEC590) was engineered to grow only on glucose while a second strain (MEC589) grew only on xylose. On a single substrate, each strain generated pyruvate at a yield of about 0.60 g/g in both continuous culture and batch culture. In a glucose‐xylose mixture under continuous culture, a consortium of both strains maintained a pyruvate yield greater than 0.60 g/g when three different concentrations of glucose and xylose were sequentially fed into the system. In a fed‐batch process, both sugars in a glucose‐xylose mixture were consumed simultaneously to accumulate 39 g/L pyruvate in less than 24 h at a yield of 0.59 g/g.

Engineering a Synthetic, Catabolically Orthogonal Coculture System for Enhanced Conversion of Lignocellulose-Derived Sugars to Ethanol

“…In past studies, engineering of glucose specialist strains has typically been achieved by deleting xylA (encoding xylose isomerase) to prevent xylose utilization. ,,− In contrast, deletion of xylR does not only prevent transcriptional activation of catabolic genes ( xylA and xylB ), but also prevents xylose uptake by further disrupting transcriptional activation of the genes responsible for xylose transport ( xylFGH ). E. coli W with deletion of xylR , WTglc, completely fermented glucose within 48 h at the maximum specific glucose utilization rate of 565 ± 9 mg gDCW –1 h –1 in batch fermentations of a glucose–xylose mixture while only 4.2 ± 0.6 g L –1 xylose was utilized over 96 h (Figure a and b).…”

“…A similar strategy was also adopted to develop a synthetic coculture composed of three distinct, hexose-specific E. coli strains to improve the simultaneous consumption of a mixture of glucose, galactose, and mannose . In addition to improving the catabolic performance of E. coli on sugar mixtures, this strategy of utilizing community engineering has furthermore proven useful for enhancing the production of various fermentation products, including lactate, succinate, and pyruvate, − as well as in other biosynthesis applications. − However, in these reported E. coli coculture systems, orthogonal catabolic functions, especially for xylose, were not further enhanced through rational genetic engineering or adaptation, thus leading to low utilization rates for sugar mixtures and suboptimal production metrics.…”

Removal of aromatic inhibitors produced from lignocellulosic hydrolysates by Acinetobacter baylyi ADP1 with formation of ethanol by Kluyveromyces marxianus

“…7, where appropriate strain(s) are introduced into a second reactor to convert the sugar mixture into a product. In each reactor of this “fully continuous” configuration, the microbes must be growing, and thus, the product must be a growth-associated product such as pyruvate [26]. One critical aspect of implementing a two-stage detoxification/conversion process using any operational mode is that the first inhibitor-consuming microbe(s) must be unable to metabolize the product under the environmental conditions found in the second stage.…”

Selective Aerobic Oxidation of Lactate to Pyruvate Catalyzed by Vanadium‐Nitrogen‐Doped Carbon Nanosheets

“…In particular, pyruvate esters are important chemicals used in many sectors, including agrochemicals, foodstuffs, cosmetics, and pharmaceuticals . Pyruvate is a key metabolite, and is biologically produced from sugars by microorganisms . However, the main drawback of metabolic route is its low productivity and costly purification of pyruvate…”