Ethylene glycol and glycolic acid production from xylonic acid by Enterobacter cloacae

Abstract

Background: Biological routes for ethylene glycol production have been developed in recent years by constructing the synthesis pathways in different microorganisms. However, no microorganisms have been reported yet to produce ethylene glycol naturally.Results: Xylonic acid utilizing microorganisms were screened from natural environments, and an Enterobacter cloacae strain was isolated. The major metabolites of this strain were ethylene glycol and glycolic acid. However, the metabolites were switched to 2,3-butanediol, acetoin or acetic acid when this strain was cultured with other carbon sources. The metabolic pathway of ethylene glycol synthesis from xylonic acid in this bacterium was identified. Xylonic acid was converted to 2-dehydro-3-deoxy-d-pentonate catalyzed by d-xylonic acid dehydratase. 2-Dehydro-3-deoxy-d-pentonate was converted to form pyruvate and glycolaldehyde, and this reaction was catalyzed by an aldolase. d-Xylonic acid dehydratase and 2-dehydro-3-deoxy-d-pentonate aldolase were encoded by yjhG and yjhH, respectively. The two genes are part of the same operon and are located adjacent on the chromosome. Besides yjhG and yjhH, this operon contains four other genes. However, individually inactivation of these four genes had no effect on either ethylene glycol or glycolic acid production; both formed from glycolaldehyde. YqhD exhibits ethylene glycol dehydrogenase activity in vitro. However, a low level of ethylene glycol was still synthesized by E. cloacae ΔyqhD. Fermentation parameters for ethylene glycol and glycolic acid production by the E. cloacae strain were optimized, and aerobic cultivation at neutral pH were found to be optimal. In fed batch culture, 34 g/L of ethylene glycol and 13 g/L of glycolic acid were produced in 46 h, with a total conversion ratio of 0.99 mol/mol xylonic acid. Conclusions:A novel route of xylose biorefinery via xylonic acid as an intermediate has been established.

Characteristics of Gut Microbiota in Patients with GH-Secreting Pituitary Adenoma

“…According to existing reports, the increase of Oscillibacter is associated with inflammatory status as well as increased permeability of the gastrointestinal tract ( 33 – 37 ). Meanwhile, in addition to acting as an opportunistic pathogen ( 38 ), the expanded Enterobacter may reinforce the fermentation and utilization of various carbon sources to produce metabolites such as acetic acid ( 39 – 41 ). On the contrary, the general reduction of other genera, consistent with decreased biodiversity, might confront patients with susceptibility to opportunistic pathogens ( 42 ).…”

Xylose Metabolism in Bacteria—Opportunities and Challenges towards Efficient Lignocellulosic Biomass-Based Biorefineries

“…Additionally, native ethylene glycol and glycolic acid producers such as Enterobacter cloacae have been used. This strain is not able to produce these two metabolites from xylose; however, it can use xylonic acid as a substrate for ethylene glycol and glycolate production [99].…”

Production of Ethylene Glycol from Glycerol Using an In Vitro Enzymatic Cascade

“…The yields of ethylene glycol from D-glucose were only 0.09 g/g by engineered Corynebacterium glutamicum and 0.14 g/g by engineered E. coli [14,31]. Glycolaldehyde, the direct precursor of ethylene glycol, can be produced from D-xylose or xylonic acid through the Dahms pathway [12,29,32]. Due to the carbon loss induced by the coproduction of pyruvate, the theoretical yield of ethylene glycol from D-xylose was 0.413 g/g.…”

“…A higher yield of 0.40 g/g ethylene glycol from D-xylose was obtained by further improving the redox balance of the Dahms pathway, overexpressing FucO and YjhG, and deleting the by-products encoding genes aldA and arcA [29]. Recently, a cell-free bioreaction scheme was also reported to generate ethylene glycol from D-xylose, with a yield of Some biotechnological routes have been developed for the production of ethylene glycol from biomass-derived carbohydrates [12][13][14]19,29,[31][32][33][34][35] (Table 1). For example, D-glucose was used as a substrate to produce ethylene glycol via the extension of the serine biosynthesis pathway.…”