Multivariate modular metabolic engineering and medium optimization for vitamin B_(12)production by Escherichia coli

Vitamin B_(12)is a complex compound synthesized by microorganisms.The industrial production of vitamin B_(12)relies on specific microbial fermentation processes.E.coli has been utilized as a host for the de novo biosynthesis of vitamin B_(12),incorporating approximately 30 heterologous genes.However,a metabolic imbalance in the intricate pathway significantly limits vitamin B_(12)production.In this study,we employed multivariate modular metabolic engineering to enhance vitamin B_(12)production in E.coli by manipulating two modules comprising a total of 10 genes within the vitamin B_(12)biosynthetic pathway.These two modules were integrated into the chromosome of a chassis cell,regulated by T7,J23119,and J23106 promoters to achieve combinatorial pathway optimization.The highest vitamin B_(12)titer was attained by engineering the two modules controlled by J23119 and T7 promoters.The inclusion of yeast powder to the fermentation medium increased the vitamin B_(12)titer to 1.52 mg/L.This enhancement was attributed to the effect of yeast powder on elevating the oxygen transfer rate and augmenting the strain’s isopropyl-β-D-1-thiogalactopyranoside(IPTG)tolerance.Ultimately,vitamin B_(12)titer of 2.89 mg/L was achieved through scaled-up fermentation in a 5-liter fermenter.The strategies reported herein will expedite the development of industry-scale vitamin B_(12)production utilizing E.coli.

Recent advances in microbial production of phenolic compounds

Phenolic compounds(PCs)are a group of compounds with various applications in nutraceutical,pharmaceutical and cosmetic industries.Their supply by plant extraction and chemical synthesis is often limited by low yield and high cost.Microbial production represents as a promising alternative for efficient and sustainable production of PCs.In this review,we summarize recent advances in this field,which include enzyme mining and engineering to construct artificial pathways,balance of enzyme expression to improve pathway efficiency,coculture engineering to alleviate metabolic burden and side-reactions,and the use of genetic circuits for dynamic regulation and high throughput screening.Finally,current challenges and future perspectives for efficient production of PCs are also discussed.

Modularly engineered prodrug-nanoassemblies for cancer therapy:Nonpharmacological moiety dominating delivery fates

Self-engineered small-molecule prodrug-nanoassemblies have emerged as promising nanomedicines for cancer treatment.Modular design of prodrug molecules is crucial to guarantee the favorable assembly stability,tumor-specific prodrug activation,and satisfactory antitumor effect.However,too much attention has been paid to the pharmacophores and chemical linkages in prodrug molecules while neglects the vital roles of nonpharmacological moieties.Herein,we found that iso-carbon fatty acids with different number,position,and cis-trans configuration of double bonds dramatically affect the nanoassembly feature and drug delivery fates of thioether-linked paclitaxel prodrug-nanoassemblies.Particularly,the number and cis-trans configuration of double bonds in fatty acid moieties not only dominate the self-assembly ability and colloidal stability of prodrugs,but also exert significant influences on the pharmacokinetics,prodrug activation,and antitumor activity of prodrug-nanoassemblies.Finally,oleic acid with one cis double bond stands out as the optimal nonpharmacological moiety for thioether-linked paclitaxel prodrugnanoassemblies.This study elucidates the crucial roles of nonpharmacological moieties in prodrugs,and provides new insights into the modular design of prodrug-based nanomedicines for cancer therapy.

Structural diversification of bioactive bibenzyls through modular co-culture leading to the discovery of a novel neuroprotective agent

Bibenzyls,a kind of important plant polyphenols,have attracted growing attention for their broad and remarkable pharmacological activities.However,due to the low abundance in nature,uncontrollable and environmentally unfriendly chemical synthesis processes,these compounds are not readily accessible.Herein,one high-yield bibenzyl backbone-producing Escherichia coli strain was constructed by using a highly active and substrate-promiscuous bibenzyl synthase identified from Dendrobium officinale in combination with starter and extender biosynthetic enzymes.Three types of efficiently postmodifying modular strains were engineered by employing methyltransferases,prenyltransferase,and glycosyltransferase with high activity and substrate tolerance together with their corresponding donor biosynthetic modules.Structurally different bibenzyl derivatives were tandemly and/or divergently synthesized by co-culture engineering in various combination modes.Especially,a prenylated bibenzyl derivative(12)was found to be an antioxidant that exhibited potent neuroprotective activity in the cellular and rat models of ischemia stroke.RNA-seq,quantitative RT-PCR,and Western-blot analysis demonstrated that 12 could up-regulate the expression level of an apoptosis-inducing factor,mitochondria associated 3(Aifm3),suggesting that Aifm3 might be a new target in ischemic stroke therapy.This study provides a flexible plug-and-play strategy for the easy-to-implement synthesis of structurally diverse bibenzyls through a modular co-culture engineering pipeline for drug discovery.