Engineering Escherichia coli for utilization of PET degraded ethylene glycol as sole feedstock.

From both economic and environmental perspectives, ethylene glycol, the principal constituent in the degradation of PET, emerges as an optimal feedstock for microbial cell factories. Traditional methods for constructing Escherichia coli chassis cells capable of utilizing ethylene glycol as a non-sugar feedstock typically involve overexpressing the genes fucO and aldA. However, these approaches have not succeeded in enabling the exclusive use of ethylene glycol as the sole source of carbon and energy for growth. Through ultraviolet radiation-induced mutagenesis and subsequent laboratory adaptive evolution, an EG02 strain emerged from E. coli MG1655 capable of utilizing ethylene glycol as its sole carbon and energy source, demonstrating an uptake rate of 8.1 ± 1.3 mmol/gDW h. Comparative transcriptome analysis guided reverse metabolic engineering, successfully enabling four wild-type E. coli strains to metabolize ethylene glycol exclusively. This was achieved through overexpression of the gcl, hyi, glxR, and glxK genes. Notably, the engineered E. coli chassis cells efficiently metabolized the 87 mM ethylene glycol found in PET enzymatic degradation products following 72 h of fermentation. This work presents a practical solution for recycling ethylene glycol from PET waste degradation products, demonstrating that simply adding M9 salts can effectively convert them into viable raw materials for E. coli cell factories. Our findings also emphasize the significant roles of genes associated with the glycolate and glyoxylate degradation I pathway in the metabolic utilization of ethylene glycol, an aspect frequently overlooked in previous research.

Exploring the De Novo NMN Biosynthesis as an Alternative Pathway to Enhance NMN Production.

Nicotinamide mononucleotide (NMN) serves as a precursor for NAD+ synthesis and has been shown to have positive effects on the human body. Previous research has predominantly focused on the nicotinamide phosphoribosyltransferase-mediated route (NadV-mediated route) for NMN biosynthesis. In this study, we have explored the de novo NMN biosynthesis route as an alternative pathway to enhance NMN production. Initially, we systematically engineered Escherichia coli to enhance its capacity for NMN synthesis and accumulation, resulting in a remarkable over 100-fold increase in NMN yield. Subsequently, we progressively enhanced the de novo NMN biosynthesis route to further augment NMN production. We screened and identified the crucial role of MazG in catalyzing the enzymatic cleavage of NAD+ to NMN. And the de novo NMN biosynthesis route was optimized and integrated with the NadV-mediated NMN biosynthetic pathways, leading to an intracellular concentration of 844.10 ± 17.40 µM NMN. Furthermore, the introduction of two transporters enhanced the uptake of NAM and the excretion of NMN, resulting in NMN production of 1293.73 ± 61.38 µM. Finally, by engineering an E. coli strain with optimized PRPP synthetase, we achieved the highest NMN production, reaching 3067.98 ± 27.25 µM after 24 h of fermentation at the shake flask level. In addition to constructing an efficient E. coli cell factory for NMN production, our findings provide new insights into understanding the NAD+ salvage pathway and its role in energy metabolism within E. coli.

Promising Anti-Inflammatory Tools: Biomedical Efficacy of Lipoxins and Their Synthetic Pathways.

Lipoxins (LXs) have attracted widespread attention as a class of anti-inflammatory lipid mediators that are produced endogenously by the organism. LXs are arachidonic acid (ARA) derivatives that include four different structures: lipoxin A4 (LXA4), lipoxin B4 (LXB4), and the aspirin-induced differential isomers 15-epi-LXA4 and 15-epi-LXB4. Because of their unique biological activity of reducing inflammation in the body, LXs have great potential for neuroprotection, anti-inflammatory treatment of COVID-19, and other related diseases. The synthesis of LXs in vivo is achieved through the action of lipoxygenase (LO). As a kind of important enzyme, LO plays a major role in the physiological processes of living organisms in mammals and functions in some bacteria and fungi. This suggests new options for the synthesis of LXs in vitro. Meanwhile, there are other chemical and biochemical methods to synthesize LXs. In this review, the recent progress on physiological activity and synthetic pathways of LXs is summarized, and new insights into the synthesis of LXs in vitro are provided.