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Yersiniabactin (Ybt) is a mixed nonribosomal peptide-polyketide natural product that binds a wide range of metals with the potential to impact processes requiring metal retrieval and removal. In this work, we substantially improved upon the heterologous production of Ybt and an associated anthranilate analog through systematic screening and optimization of culture medium components. Specifically, a Plackett-Burman design-of-experiments methodology was used to screen 22 components and to determine those contributing most to siderophore production. L-cysteine, L-serine, glucose, and casamino acids significantly contributed to the production of both compounds. Using this approach together with metabolic engineering of the base biosynthetic process, Ybt and the anthranilate analog titers were increased to 867 ± 121 mg/L and 16.6 ± 0.3 mg/L, respectively, an increase of ∼38 and ∼79-fold relative to production in M9 medium. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1193-1200, 2017., (© 2017 American Institute of Chemical Engineers.)

E. coli has become a common host for the heterologous biosynthesis of natural products that demonstrate therapeutic value but suffer from access challenges posed by native production hosts. This review will highlight recent examples of heterologous products produced using E. coli. An emphasis will be placed on tools at the cellular and process levels to enable, improve, and alter production efforts. At the cellular scale, summaries of the process to enable heterologous biosynthesis will be supplemented with strategies (synthetic biology and metabolic engineering) to improve production levels. Process engineering strategies such as precursor-directed biosynthesis will also be highlighted in analog formation cases. In summary, the article will provide a recent overview of heterologous production efforts using E. coli and the relationship of the products produced to therapeutic applications., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

In this report, the heterologous production of salicylate (SA) is the basis for metabolic extension to salicylate 2-O-β-d-glucoside (SAG), a natural product implicated in plant-based defense mechanisms. Production was optimized through a combination of metabolic engineering, gene expression variation, and co-culture design. When combined, SA and SAG production titers reached ~0.9g/L and ~2.5g/L, respectively. The SAG compound was then tested for anti-inflammatory properties relative to SA and acetylsalicylate (aspirin). Results indicate comparable activity between SAG and aspirin in reducing nitric oxide (NO) and reactive oxygen species (ROS) from macrophage cells while no discernable negative effects on cellular viability were observed., (Copyright © 2016 International Metabolic Engineering Society. Published by Elsevier Inc. All rights reserved.)

Biosynthesis of complex natural products like polyketides and nonribosomal peptides using Escherichia coli as a heterologous host provides an opportunity to access these molecules. The value in doing so stems from the fact that many compounds hold some therapeutic or other beneficial property and their original production hosts are intractable for a variety of reasons. In this work, metabolic engineering and induction variable optimization were used to increase production of the polyketide-nonribosomal peptide compound yersiniabactin, a siderophore that has been utilized to selectively remove metals from various solid and aqueous samples. Specifically, several precursor substrate support pathways were altered through gene expression and exogenous supplementation in order to boost production of the final compound. The gene expression induction process was also analyzed to identify the temperatures and inducer concentrations resulting in highest final production levels. When combined, yersiniabactin production was extended to ∼175 mg L -1 . © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1412-1417, 2016., (© 2016 American Institute of Chemical Engineers.)

The production of the mixed nonribosomal peptide-polyketide natural product yersiniabactin (Ybt) has been established using E. coli as a heterologous host. In this study, precursor-directed biosynthesis was used to generate five new analogs of Ybt, demonstrating the flexibility of the heterologous system and the biosynthetic process in allowing compound diversity. A combination of biosynthetic and cellular engineering was then used to influence the production metrics of the resulting analogs. First, the cellular levels and activity of FadL, a hydrocarbon transport protein, were tested for subsequent influence upon exogenous precursor uptake and Ybt analog production with a positive correlation observed between FadL over-production and analog formation. Next, a Ybt biosynthetic editing enzyme was removed from the heterologous system which decreased native compound production but increased analog formation. A final series of experiments enhanced endogenous anthranilate towards complete pathway formation of the associated analog which showed a selective ability to bind gold., (© 2015 Wiley Periodicals, Inc.)

Yersiniabactin (Ybt) is a mixed nonribosomal peptide-polyketide natural product natively produced by the pathogen Yersinia pestis. The compound enables iron scavenging capabilities upon host infection and is biosynthesized by a nonribosomal peptide synthetase featuring a polyketide synthase module. This pathway has been engineered for expression and biosynthesis using Escherichia coli as a heterologous host. In the current work, the biosynthetic process for Ybt formation was improved through the incorporation of a dedicated step to eliminate the need for exogenous salicylate provision. When this improvement was made, the compound was tested in parallel applications that highlight the metal-chelating nature of the compound. In the first application, Ybt was assessed as a rust remover, demonstrating a capacity of ∼40% compared to a commercial removal agent and ∼20% relative to total removal capacity. The second application tested Ybt in removing copper from a variety of nonbiological and biological solution mixtures. Success across a variety of media indicates potential utility in diverse scenarios that include environmental and biomedical settings., (Copyright © 2015, American Society for Microbiology. All Rights Reserved.)