Microbial biosynthesis of the anticoagulant precursor 4-hydroxycoumarin

Mailuo Shutong pills inhibit neuroinflammation by regulating glucose metabolism disorders to protect mice from cerebral ischemia-reperfusion injury

ETHNOPHARMACOLOGICAL RELEVANCE

Mailuo Shutong Pill (MLST), a traditional Chinese medicine (TCM), has been widely used for clearing heat and detoxifying, eliminating stasis and dredging meridians, dispelling dampness and diminishing swelling. Earlier study found that MLST could improve cerebral ischemic-reperfusion injury, however, the potential mechanism has not been well evaluated.

AIM OF STUDY

In this study, a well established and widely used mice model of middle cerebral artery occlusion/reperfusion (MCAO/R) was preformed to evaluate the protective function of MLST on cerebral ischemic-reperfusion injury and further discuss the potential pharmacological mechanisms.

MATERIALS AND METHODS

Chemical profiling of MLST was analyzed based on Ultra-high-performance liquid chromatography electrospray ionization orbitrap tandem mass spectrometry. ICR mice were challenged by MCAO/R surgery. The protective effect of MLST on MCAO/R injury was evaluated by neurological deficit score, cerebral infarct rate, brain water content, H&E and nissl staining. The blood-brain barrier (BBB) integrity was detected by Evans blue staining. The potential pharmacological mechanism of MLST in treating MCAO/R injury was further elucidated by the methods of proteomics, central carbon targeted metabolomics, as well as Western blot. Immunohistochemistry was used to detect the microglia infiltration, enzyme linked immunosorbent assay (ELISA) kit was explored to evaluate the content of IL-1β, TNF-α and IL-6 in brain tissue, and Western blot was used to detect proteins expression in brain tissue.

RESULTS

A total of 76 chemical compounds have been determined in MLST. MLST effectively protected mice from MCAO/R injury, which was confirmed by lower neurological deficit score, cerebral infarct rate, brain water content and nissl body loss, and improved brain pathology. Meanwhile, MLST upregulated the expression of ZO-1, Occludin and Claudin 5 by downregulating the ratio of TIMP1/MMP9 to suppress the entrance of Evans blue to brain tissue, indicating that MLST maintained the integrity of BBB. Further studies indicated that MLST inhibited the inflammatory level of brain tissue by inhibiting microglia infiltration and downregulating NLRP3 inflammasome signaling pathway. The results of proteomics, Western blot, and central carbon targeted metabolomics confirmed that MLST regulated Glycolysis/Gluconogenesis, Pyruvate metabolism and TCA cycle in brain tissue of mice with MCAO/R.

CONCLUSION

MLST inhibits neuroinflammation by regulating glucose metabolism disorders to interfere with immune metabolism reprogramming and inhibit the NLRP3 inflammasome signaling pathway, and finally improve cerebral ischemia-reperfusion injury. This study confirms that MLST is a potential drug for treating Cerebral ischemic stroke.

Integration Site Library for Efficient Construction of Plasmid-Free Microbial Cell Factories in Escherichia coli

Enhanced production stability and efficiency along with a decrease in production costs are required to build efficient microbial cell factories. Target genes can be integrated into the genome to enhance genetic stability, reduce reliance on antibiotics, and alleviate the metabolic burden. However, selecting the optimal insertion site for the desired gene expression levels remains challenging. Therefore, 18 commonly usedEscherichia coliintegration sites were systematically characterized in this study. Promoters of different strengths were combined with integration sites, yielding a differential intensity range of up to 93-fold. This indicated the versatility and precision of this approach for controlling gene expression levels. Referring to the library, pathway genes were strategically integrated into theE. coligenome based on their respective expression levels. Genetically stable and highly efficient engineered strains that could biosynthesize arbutin and p-aminobenzoic acid were constructed.

Rational and Semirational Approaches for Engineering Salicylate Production in Escherichia coli

Salicylate plays a pivotal role as a pharmaceutical intermediate in drugs, such as aspirin and lamivudine. The low catalytic efficiency of key enzymes and the inherent toxicity of salicylates to cells pose significant challenges to large-scale microbial production. In this study, we introduced the salicylate synthase Irp9 into an l-phenylalanine-producing Escherichia coli, constructing the shortest salicylate biosynthetic pathway. Subsequent protein engineering increased the catalytic efficiency of Irp9 by 33.5%. Furthermore, by integrating adaptive evolution with transcriptome analysis, we elucidated the crucial mechanism of efflux proteins in salicylate tolerance. The elucidation of this mechanism guided us in the targeted modification of these transport proteins, achieving a reported maximum level of 3.72 g/L of salicylate in a shake flask. This study highlights the importance of efflux proteins for enhancing the productivity of microbial cell factories in salicylate production, which also holds potential for application in the green synthesis of other phenolic acids.

Establishing a coumarin production platform by protein and metabolic engineering

Coumarins are a vast family of natural products with diverse biological activities. Cinnamyl-CoA ortho-hydroxylases (CCHs) catalyze the gateway and rate-limiting step in coumarin biosynthesis. However, engineering CCHs is challenging due to the large size of the substrates and the vague structure-activity relationship. Herein, directed evolution and structure-guided engineering were performed to engineer a CCH (AtF6'H from Arabidopsis thaliana) using a fluorescence-based screening method, yielding the transplantable surface mutations and the substrate-specific pocket mutations with improved activity. Structural analysis and molecular dynamics simulations elucidated the conformational changes that led to increased catalytic efficiency. Applying appropriate variants with the optimized upstream biosynthetic pathways improved the titers of three simple coumarins by 5 to 22-fold. Further introducing glycosylation modules resulted in the production of four coumarin glucosides, among which the titer of aesculin was increased by 15.7-fold and reached 3 g/L in scale-up fermentation. This work unleashed the potential of CCHs and established an Escherichia coli platform for coumarins production.

Cobalt-catalyzed three-component assembly of aromatic oximes with substituted dienes and formaldehyde

A cobalt-catalyzed three-component assembly of substituted aryl oximes with dienes and formaldehyde via C-H bond activation is described. This protocol affords highly regio- and chemoselective substituted homoallylic alcohols with moderate-to-excellent yields. The scope of this protocol has been extensively explored with various substituted aryl ketoximes and aldoximes. Butadiene and internally substituted dienes are also well compatible for this transformation. A plausible reaction mechanism is proposed to account for the present reaction and is supported by deuterium labeling studies.

Advancing microbial production through artificial intelligence-aided biology

Microbial cell factories (MCFs) have been leveraged to construct sustainable platforms for value-added compound production. To optimize metabolism and reach optimal productivity, synthetic biology has developed various genetic devices to engineer microbial systems by gene editing, high-throughput protein engineering, and dynamic regulation. However, current synthetic biology methodologies still rely heavily on manual design, laborious testing, and exhaustive analysis. The emerging interdisciplinary field of artificial intelligence (AI) and biology has become pivotal in addressing the remaining challenges. AI-aided microbial production harnesses the power of processing, learning, and predicting vast amounts of biological data within seconds, providing outputs with high probability. With well-trained AI models, the conventional Design-Build-Test (DBT) cycle has been transformed into a multidimensional Design-Build-Test-Learn-Predict (DBTLP) workflow, leading to significantly improved operational efficiency and reduced labor consumption. Here, we comprehensively review the main components and recent advances in AI-aided microbial production, focusing on genome annotation, AI-aided protein engineering, artificial functional protein design, and AI-enabled pathway prediction. Finally, we discuss the challenges of integrating novel AI techniques into biology and propose the potential of large language models (LLMs) in advancing microbial production.

Network pharmacology and experimental verification to explore the anti-superficial thrombophlebitis mechanism of Mailuo shutong pill

ETHNOPHARMACOLOGICAL RELEVANCE

Mailuo shutong pill (MLST) has been widely used in clinical treatment of superficial thrombotic phlebitis (STP). Nevertheless, the major active components of MLST and the mechanism of synergistic action have not been reported.

AIM OF THE STUDY

The present study aimed to evaluate the improving effects and the underlying mechanism of MLST on mannitol-induced STP in rabbits.

MATERIAL AND METHODS

In this study, Ultrahigh-performance liquid chromatography electrospray ionization quadrupole-exactive orbitrap mass spectrometry (UHPLC-ESI-Q-Exactive-Orbitrap-MS) was used to analyze and identify the chemical composition of MLST and the prototype components absorbed into the blood. Then, according to the prototype components in serum, the targets and mechanisms of MLST were explored by applying network pharmacology. The rabbit model of STP was established by injecting 20% mannitol into bilateral auricular vein. The pathological changes of rabbit ear tissues, inflammatory factors, coagulation function and hemorheology were detected. In addition, molecular docking verified the interaction between the main active ingredient and the key target. Finally, the PI3K/AKT pathway and its regulated downstream pathways were verified by Western blot.

RESULTS

A total of 96 MLST components and 53 prototypical components absorbed into the blood were successfully identified. Based on network pharmacology, PI3K/AKT pathway and 10 chemical components closely related to this pathway were obtained. Hematoxylin-eosin (HE) staining results indicated that MLST effectively improved of the pathological damage of ear tissues. MLST decreased levels of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6 and C-reactive protein (CRP). The expression of platelets (PLT) and fibrinogen concentration (FIB) was decreased, while prothrombin time (PT) and activated partial thromboplastin time (APTT) were prolonged. In addition, the plasma viscosity and whole blood viscosity in the MLST groups were significantly decreased. The more important discovery was that the expressions of P-PI3K, VEGF, P-AKT, P-IκB-α, P-NF-κB, NLRP3, ASC, Cleaved IL-1β and Cleaved Caspase-1 were effectively reversed after treatment with MLST.

CONCLUSIONS

This study comprehensively analyzed and characterized the chemical composition of MLST and the prototypical components absorbed into the blood. This study strongly confirmed the pharmacodynamic effect of MLST on STP. More importantly, this pharmacodynamic effect was achieved through inhibition of the PI3K/AKT pathway and its regulated NF-κB and NLRP3 pathways.

A self-regulated network for dynamically balancing multiple precursors in complex biosynthetic pathways

Microbial synthesis has emerged as a promising and sustainable alternative to traditional chemical synthesis and plant extraction. However, the competition between synthetic pathways and central metabolic pathways for cellular resources may impair final production efficiency. Moreover, when the synthesis of target product requires multiple precursors from the same node, the conflicts of carbon flux have further negative impacts on yields. In this study, a self-regulated network was developed to relieve the competition of precursors in complex synthetic pathways. Using 4-hydroxycoumarin (4-HC) synthetic pathway as a proof of concept, we employed an intermediate as a trigger to dynamically rewire the metabolic flux of pyruvate and control the expression levels of genes in 4-HC synthetic pathway, achieving self-regulation of multiple precursors and enhanced titer. Transcriptomic analysis results additionally demonstrated that the gene transcriptional levels of both pyruvate kinase PykF and synthetic pathway enzyme SdgA dynamically changed according to the intermediate concentrations. Overall, our work established a self-regulated network to dynamically balance the metabolic flux of two precursors in 4-HC biosynthesis, providing insight into balancing biosynthetic pathways where multiple precursors compete and interfere with each other.

Simple phenylpropanoids: recent advances in biological activities, biosynthetic pathways, and microbial production

Covering: 2000 to 2023Simple phenylpropanoids are a large group of natural products with primary C6-C3 skeletons. They are not only important biomolecules for plant growth but also crucial chemicals for high-value industries, including fragrances, nutraceuticals, biomaterials, and pharmaceuticals. However, with the growing global demand for simple phenylpropanoids, direct plant extraction or chemical synthesis often struggles to meet current needs in terms of yield, titre, cost, and environmental impact. Benefiting from the rapid development of metabolic engineering and synthetic biology, microbial production of natural products from inexpensive and renewable sources provides a feasible solution for sustainable supply. This review outlines the biological activities of simple phenylpropanoids, compares their biosynthetic pathways in different species (plants, bacteria, and fungi), and summarises key research on the microbial production of simple phenylpropanoids over the last decade, with a focus on engineering strategies that seem to hold most potential for further development. Moreover, constructive solutions to the current challenges and future perspectives for industrial production of phenylpropanoids are presented.

The Construction of the Self-Induced Sal System and Its Application in Salicylic Acid Production

The design and construction of more complex and delicate genetic control circuits suffer from poor orthogonality in quorum sensing (QS) systems. The Sal system, which relies on salicylic acid as a signaling molecule, is an artificially engineered regulatory system with a structure that differs significantly from that of natural QS signaling molecules. Salicylic acid is an important drug precursor, mainly used in the production of drugs such as aspirin and anti-HIV drugs. However, there have been no reports on the construction of a self-induced Sal system in single cells. In this study, a high-copy plasmid backbone was used to construct the regulatory proteins and a self-induced promoter of salicylic acid in E. coli by adjusting the precise regulation of key gene expression; the sensitivity and induction range of this system were improved. Subsequently, the exogenous gene pchBA was introduced in E. coli to extend the shikimate pathway and synthesize salicylic acid, resulting in the construction of the first complete self-induced Sal system. Finally, the self-induced Sal System was combined with artificial trans-encoded sRNAs (atsRNAs) to repress the growth-essential gene ppc and accumulate the precursor substance PEP, thereby increasing the titer of salicylic acid by 151%. This construction of a self-induced artificial system introduces a new tool for selecting communication tools and induction systems in synthetic biology and metabolic engineering, but also demonstrates a self-inducible pathway design strategy for salicylic acid biosynthesis.

Advances in regulating vitamin K2 production through metabolic engineering strategies

Vitamin K2 (menaquinone, VK2, MK) is an essential lipid-soluble vitamin that plays critical roles in inhibiting cell ferroptosis, improving blood clotting, and preventing osteoporosis. The increased global demand for VK2 has inspired interest in novel production strategies. In this review, various novel metabolic regulation strategies, including static and dynamic metabolic regulation, are summarized and discussed. Furthermore, the advantages and disadvantages of both strategies are analyzed in-depth to highlight the bottlenecks facing microbial VK2 production on an industrial scale. Finally, advanced metabolic engineering biotechnology for future microbial VK2 production will also be discussed. In summary, this review provides in-depth information and offers an outlook on metabolic engineering strategies for VK2 production.

High-yield production of β-arbutin by identifying and eliminating byproducts formation

β-Arbutin is a plant-derived glycoside and widely used in cosmetic and pharmaceutical industries because of its safe and effective skin-lightening property as well as anti-oxidant, anti-microbial, and anti-inflammatory activities. In recent years, microbial fermentation has become a highly promising method for the production of β-arbutin. However, this method suffers from low titer and low yield, which has become the bottleneck for its widely industrial application. In this study, we used β-arbutin to demonstrate methods for improving yields for industrial-scale production in Escherichia coli. First, the supply of precursors phosphoenolpyruvate and uridine diphosphate glucose was improved, leading to a 4.6-fold increase in β-arbutin production in shaking flasks. The engineered strain produced 36.12 g/L β-arbutin with a yield of 0.11 g/g glucose in a 3-L bioreactor. Next, based on the substrate and product's structural similarity, an endogenous O-acetyltransferase was identified as responsible for 6-O-acetylarbutin formation for the first time. Eliminating the formation of byproducts, including 6-O-acetylarbutin, tyrosine, and acetate, resulted in an engineered strain producing 43.79 g/L β-arbutin with a yield of 0.22 g/g glucose in fed-batch fermentation. Thus, the yield increased twofold by eliminating byproducts formation. To the best of our knowledge, this is the highest titer and yield of β-arbutin ever reported, paving the way for the industrial production of β-arbutin. This study demonstrated a systematic strategy to alleviate undesirable byproduct accumulation and improve the titer and yield of target products. KEY POINTS: • A systematic strategy to improve titer and yield was showed • Genes responsible for 6-O-acetylarbutin formation were firstly identified • 43.79 g/L β-arbutin was produced in bioreactor, which is the highest titer so far.

Dynamic Metabolic Control: From the Perspective of Regulation Logic

Establishing microbial cell factories has become a sustainable and increasingly promising approach for the synthesis of valuable chemicals. However, introducing heterologous pathways into these cell factories can disrupt the endogenous cellular metabolism, leading to suboptimal production performance. To address this challenge, dynamic pathway regulation has been developed and proven effective in improving microbial biosynthesis. In this review, we summarized typical dynamic regulation strategies based on their control logic. The applicable scenarios for each control logic were highlighted and perspectives for future research direction in this area were discussed.

Identifying, Characterizing, and Engineering a Phenolic Acid-Responsive Transcriptional Factor from Bacillus amyloliquefaciens

Transcriptional factors-based biosensors are commonly used in metabolic engineering for inducible control of gene expression and related applications such as high-throughput screening and dynamic pathway regulations. Mining for novel transcriptional factors is essential for expanding the usability of these toolsets. Here, we report the identification, characterization, and engineering of a phenolic acid responsive regulator PadR from Bacillus amyloliquefaciens (BaPadR). This BaPadR-based biosensor system showed a unique ligand preference and exhibited a high output strength comparable to that of commonly used inducible expression systems. Through engineering the DNA binding region of BaPadR, we further enhanced the dynamic range of the biosensor system. The DNA sequences that are responsible for BaPadR recognition were located by promoter truncation and hybrid promoter building. To further explore the tunability of the sensor system, base substitutions were performed on the BaPadR binding region of the phenolic acid decarboxylase promoter (PpadC) and the hybrid promoter. This novel biosensor system can serve as a valuable tool in future synthetic biology applications.

Improved cryptic plasmids in probiotic Escherichia coli Nissle 1917 for antibiotic-free pathway engineering

The engineered probiotic Escherichia coli Nissle 1917 (EcN) is expected to be employed in the diagnosis and treatment of various diseases. However, the introduced plasmids typically require antibiotics to maintain genetic stability, and the cryptic plasmids in EcN are usually eliminated to avoid plasmid incompatibility which may change the inherent probiotic characteristics. Here, we provided a simple design to minimize the genetic change of probiotics by eliminating native plasmids and reintroducing the recombinants carrying functional genes. Specific insertion sites in the vectors showed significant differences in the expression of fluorescence proteins. Selected integration sites were applied in the de novo synthesis of salicylic acid, leading to a titer of 142.0 ± 6.0 mg/L in a shake flask with good production stability. Additionally, the design successfully realized the biosynthesis of ergothioneine (45 mg/L) by one-step construction. This work expands the application scope of native cryptic plasmids to the easy construction of functional pathways. KEY POINTS: • Cryptic plasmids of EcN were designed to express exogenous genes • Insertion sites with different expression intensities in cryptic plasmids were provided • Target products were stably produced by engineering cryptic plasmids.

Effective Synthesis and Biological Evaluation of Dicoumarols: Preparation, Characterization, and Docking Studies

A series of 3,3-arylidene bis (4-hydroxycoumarins) 2 were synthesized by the reaction of aromatic aldehydes with 4-hydroxycoumarin using dodecylbenzenesulfonic acid as Brønsted acid-surfactant catalyst in aqueous media and under microwave irradiation. The present method is operationally simple and the use of water as the reaction medium makes the process environmentally benign. The epoxydicoumarins 5 were then obtained with a good yield by heating 3,3'-arylidenebis-4-hydroxycoumarins 2 in acetic anhydride. Techniques such as elemental analysis, ¹H, ¹³C-¹H NMR, and infrared spectroscopy were employed to characterize these compounds. The synthesized compounds displayed good antibacterial potential against Escherichia coli (ATCC 25988), Pseudomonas aeruginosa (ATCC 27853), Klebsilla pneumonia (ATCC 700603), Staphylococcus aureus (ATCC 29213), methicillin-resistant Staphylococcus aureus (ATCC 43300) and Candida albicans (ATCC 14053). The MIC values of 23 mg/mL for compound 5e against Escherichia coli (ATCC 25988) and 17 mg/mL for 2a were observed. Furthemore, a molecular docking simulation has been performed to evaluate the antibacterial activities and the probable binding modes of the studied compounds 2a-f and 5a-g toward the active sites of a series of well known antibacterial targets. Among the investigated compounds, the binding modes and docking scores demonstrate that 2a has the most antibacterial and antifungal activities. Additionally, DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS has been tested for their ability to scavenge hydrogen peroxide and free radicals. According to our results, these compounds exhibit excellent radical scavenging properties. Furthermore, compounds 2-5 were evaluated for anti-inflammatory activity by indirect haemolytic and lipoxygenase inhibition assays and revealed good activity.

Designing artificial pathways for improving chemical production

Metabolic engineering exploits manipulation of catalytic and regulatory elements to improve a specific function of the host cell, often the synthesis of interesting chemicals. Although naturally occurring pathways are significant resources for metabolic engineering, these pathways are frequently inefficient and suffer from a series of inherent drawbacks. Designing artificial pathways in a rational manner provides a promising alternative for chemicals production. However, the entry barrier of designing artificial pathway is relatively high, which requires researchers a comprehensive and deep understanding of physical, chemical and biological principles. On the other hand, the designed artificial pathways frequently suffer from low efficiencies, which impair their further applications in host cells. Here, we illustrate the concept and basic workflow of retrobiosynthesis in designing artificial pathways, as well as the most currently used methods including the knowledge- and computer-based approaches. Then, we discuss how to obtain desired enzymes for novel biochemistries, and how to trim the initially designed artificial pathways for further improving their functionalities. Finally, we summarize the current applications of artificial pathways from feedstocks utilization to various products synthesis, as well as our future perspectives on designing artificial pathways.

A Multi-Enzyme Cascade for Efficient Production of Pyrrolidone from l-Glutamate

Pyrrolidone is a high value-added monomer and an important active drug intermediate. However, the efficient enzymatic synthesis of pyrrolidone remains a challenge. Here, we developed and reconstructed a three-enzyme cascade pathway using Escherichia coli BL21(DE3) for the production of pyrrolidone from l-glutamate (l-Glu). The carnitine-CoA ligase from Escherichia coli (EcCaiC) at a low expression level and with a low activity is regarded as the rate-limiting enzyme. Here, we obtained the best EcCaiCF380M/N430D double mutant with a kcat/Km value 1.5 times higher than that of the wild type via mechanism-based protein engineering. For this, we (i) eliminated the steric hindrance of the loop ring to improve the precatalytic conformation of the adenylation intermediate and (ii) fixed the hinge region to stabilize the closed conformation of the enzyme. Furthermore, ribosome-binding site (RBS) optimization led to an increase in the expression level of EcCaiCF380M/N430D, which was then cloned into the plasmid pET-EcCaiCF380M/N430D-DegoPPK2. Finally, under optimal induction and transformation conditions, 16.62 g/L of pyrrolidone was generated from 30 g/L l-Glu (batch feeding) within 24 h with a molar conversion rate of 95.2% and the highest productivity ever obtained, to our knowledge (0.69 g/L/h). Our findings demonstrate a strategy that is potentially attractive for the industrial production of pyrrolidone. IMPORTANCE This study developed a three-enzyme cascade pathway for the production of pyrrolidone from l-Glu. The catalytic efficiency of carnitine CoA ligase from Escherichia coli (EcCaiC) was improved by mechanism-based protein engineering, and the titer of pyrrolidone was further increased by ribosome-binding site (RBS), induction conditions, and conversion conditions optimization. Finally, we efficiently produced pyrrolidone by one pot in vivo with 95.2% conversion and 0.69 g/L/h productivity. Our study provides a new possibility for the industrial production of enzymatic synthesis of pyrrolidone.

Exploring the synthetic potential of a g-C3N4·SO3H ionic liquid catalyst for one-pot synthesis of 1,1-dihomoarylmethane scaffolds via Knoevenagel-Michael reaction

A highly promising approach for the synthesis of functionalized 1,1-dihomoarylmethane scaffolds (bis-dimedones, bis-cyclohexanediones, bis-pyrazoles, and bis-coumarins) using g-C₃N₄·SO₃H ionic liquid via Knoevenagel-Michael reaction has been developed and the synthesized derivatives were well characterized using spectral studies. The method involved the reaction of C-H activated acids with a range of aromatic aldehydes, in a 2 : 1 ratio catalyzed by a g-C₃N₄·SO₃H ionic liquid catalyst. The use of g-C₃N₄·SO₃H as a catalyst has several benefits, such as low cost, easy preparation, and high stability. It was synthesized from urea powder and chloro-sulfonic acid and was thoroughly characterized using FT-IR, XRD, SEM, and HRTEM. The present work unveils a promising and environmentally friendly method for synthesizing 1,1-dihomoarylmethane scaffolds with high yield, selectivity, and efficiency, using mild reaction conditions, no need for chromatographic separation, and short reaction times. The approach adheres to green chemistry principles and offers a viable alternative to the previously reported methods.

Shikimic acid biosynthesis in microorganisms: Current status and future direction

Shikimic acid (SA), a hydroaromatic natural product, is used as a chiral precursor for organic synthesis of oseltamivir (Tamiflu®, an antiviral drug). The process of microbial production of SA has recently undergone vigorous development. Particularly, the sustainable construction of recombinant Corynebacterium glutamicum (141.2 g/L) and Escherichia coli (87 g/L) laid a solid foundation for the microbial fermentation production of SA. However, its industrial application is restricted by limitations such as the lack of fermentation tests for industrial-scale and the requirement of growth-limiting factors, antibiotics, and inducers. Therefore, the development of SA biosensors and dynamic molecular switches, as well as genetic modification strategies and optimization of the fermentation process based on omics technology could improve the performance of SA-producing strains. In this review, recent advances in the development of SA-producing strains, including genetic modification strategies, metabolic pathway construction, and biosensor-assisted evolution, are discussed and critically reviewed. Finally, future challenges and perspectives for further reinforcing the development of robust SA-producing strains are predicted, providing theoretical guidance for the industrial production of SA.

Exploring and engineering PAM-diverse Streptococci Cas9 for PAM-directed bifunctional and titratable gene control in bacteria

The RNA-guided Cas9s serve as powerful tools for programmable gene editing and regulation; their targeting scopes and efficacies, however, are always constrained by the PAM sequence stringency. Most Streptococci Cas9s, including the prototype SpCas9 from S. pyogenes, specifically recognize a canonical NGG PAM via a conserved RxR PAM-binding motif within the PAM-interaction (PI) domain. Here, SpCas9-based mining unveils three distinct and rarely presented PAM-binding motifs (QxxxR, QxQ and RxQ) among Streptococci Cas9 orthologs. With the catalytically-dead QxxxR-containing SedCas9 from S. equinus, we dissect its NAG PAM specificity and elucidate its underlying recognition mechanism via computational prediction and mutagenesis analysis. Replacing the SedCas9 PI domain with alternate PAM-binding motifs rewires its PAM specificity to NGG or NAA. Moreover, a semi-rational design with minimal mutation creates a SedCas9-NQ variant showing robust activity towards expanded NNG and NAA PAMs, based upon which we engineered a compact ω-SedCas9-NQ transcriptional regulator for PAM-directed bifunctional and titratable gene control. The ω-SedCas9-NQ mediated metabolic reprogramming of endogenous genes in Escherichia coli affords a 2.6-fold increase of 4-hydroxycoumarin production. This work reveals new Cas9 scaffolds with distinct PAM-binding motifs for PAM relaxation and creates a new PAM-diverse Cas9 variant for versatile gene control in bacteria.

Metabolic Engineering of Escherichia coli for High-Level Production of Salicin

Salicin is a notable phenolic glycoside derived from plants including Salix and Populus genus and has multiple biological activities such as anti-inflammatory and antiarthritic, anticancer, and antiaging effects. In this work, we engineered production of salicin from cheap renewable carbon resources in Escherichia coli (E. coli) by extending the shikimate pathway. We first investigated enzymes synthesizing salicylate from chorismate. Subsequently, carboxylic acid reductases (CARs) from different resources were screened to achieve efficient reduction of salicylate. Third, glucosyltransferases from different sources were selected for constructing cell factories of salicin. The enzymes including salicylate synthase AmS from Amycolatopsis methanolica, carboxylic acid reductase CARse from Segniliparus rotundus, and glucosyltransferase UGT71L1 from Populous trichocarpa were overexpressed in a modified E. coli strain MG1655-U7. The engineered strain produced 912.3 ± 12.7 mg/L salicin in 72 h of fermentation. These results demonstrated the production of salicin in a microorganism and laid significant foundation for its commercialization for pharmaceutical and nutraceutical applications.

Two O-Methyltransferases Mediate Multiple Methylation Steps in the Biosynthesis of Coumarins in Cnidium monnieri

Coumarins with methoxy groups such as osthole (1), xanthotoxin (2), bergapten (3), and isopimpinellin (4) are typical bioactive ingredients of many medicinal plants. The methylation steps remain widely unknown. Herein, we report the discovery of two methyltransferases in the biosynthesis of O-methyl coumarins in Cnidium monnieri by transcriptome mining, heterologous expression, and in vitro enzymatic assays. The results reveal that (i) CmOMT1 catalyzes the methylation of osthenol (8) as the final step in the biosynthesis of 1, (ii) CmOMT2 shows the highest efficiency and preference for methylating xanthotoxol (11) to form 2, and (iii) CmOMT1 and CmOMT2 also efficiently transform bergaptol (10) and 8-hydroxybergapten (13) into 3 or 4, suggesting the CmOMTs mediate multistep methylations in the biosynthesis of linear furanocoumarins in C. monnieri.

Synthesis of Ferulenol by Engineered Escherichia coli: Structural Elucidation by Using the In Silico Tools

4-Hydroxycoumarin (4HC) has been used as a lead compound for the chemical synthesis of various bioactive substances and drugs. Its prenylated derivatives exhibit potent antibacterial, antitubercular, anticoagulant, and anti-cancer activities. In doing this, E. coli BL21(DE3)pLysS strain was engineered as the in vivo prenylation system to produce the farnesyl derivatives of 4HC by coexpressing the genes encoding Aspergillus terreus aromatic prenyltransferase (AtaPT) and truncated 1-deoxy-D-xylose 5-phosphate synthase of Croton stellatopilosus (CstDXS), where 4HC was the fed precursor. Based on the high-resolution LC-ESI(±)-QTOF-MS/MS with the use of in silico tools (e.g., MetFrag, SIRIUS (version 4.8.2), CSI:FingerID, and CANOPUS), the first major prenylated product (named compound-1) was detected and ultimately elucidated as ferulenol, in which information concerning the correct molecular formula, chemical structure, substructures, and classifications were obtained. The prenylated product (named compound-2) was also detected as the minor product, where this structure proposed to be the isomeric structure of ferulenol formed via the tautomerization. Note that both products were secreted into the culture medium of the recombinant E. coli and could be produced without the external supply of prenyl precursors. The results suggested the potential use of this engineered pathway for synthesizing the farnesylated-4HC derivatives, especially ferulenol.

Design and construction of an artificial pathway for biosynthesis of acetaminophen in Escherichia coli

Acetaminophen (AAP) is one of the most commonly used drug ingredients that possesses antipyretic and analgesic effects. As an unnatural chemical, AAP is commercially produced by chemical processes using petroleum-derived carbohydrates, such as phenol, as raw materials, which is unsustainable and eco-unfriendly. In this study, we report design and construction of an artificial biosynthetic pathway for de novo production of AAP from simple carbon source. By exploring and expanding the substrate repertoire of natural enzymes, we identified and characterized a novel p-aminobenzoic acid (p-ABA) monooxygenase and an p-aminophenol (p-AP) N-acetyltransferase, which enabled the bacterial production of AAP from p-ABA. Then, we constructed an p-ABA over-producer by screening of p-ABA synthases and enhancing glutamine availability, resulting in 836.43 mg/L p-ABA in shake flasks in E. coli. Subsequent assembly of the entire biosynthetic pathway permitted the de novo production of AAP from glycerol for the first time. Finally, pathway engineering by dynamically regulating the expression of pathway genes via a temperature-inducible controller enabled production enhancement of AAP with a titer of 120.03 mg/L. This work not only constructs a microbial platform for AAP production, but also demonstrates design and construction of artificial biosynthetic pathways via discovering novel bioreactions based on existing enzymes.

Isolation and Identification of Tyrosinase Inhibitors from Marine Algae Enteromorpha sp

:

The extract of marine green algae Enteromorpha sp. was evaluated in vitro for inhibitory activity against mushroom tyrosinase enzyme. The principle active agents i.e. coumarin; 4-hydroxycoumarin (1) and two sterols; ergosta-5,7,22-trien-3β-ol (2) & ergosterol peroxide (3) were isolated for the first time, from a crude methanol extract of Enteromorpha sp. showing anti-tyrosinase activity. Their structures were elucidated by IR, extensive NMR spectroscopy, LC-ESI-MS, Single crystal X-ray diffraction techniques. Thus, Enteromorpha sp. can be an alternative edible anti-tyrosinase agent.

Engineering the Cad pathway in Escherichia coli to produce glutarate from L-lysine

For the efficient industrial production of glutarate, an important C5 platform chemical that is widely used in the chemical and pharmaceutical industries, a five-enzyme cascade pathway was designed and reconstructed in vitro to synthesize glutarate from L-lysine. Then, the imbalanced enzyme expression levels of L-lysine decarboxylase from Escherichia coli (EcCA), putrescine aminotransferase (KpcPA) and γ-aminovaleraldehyde dehydrogenase (KpcPD) from Klebsiella pneumoniae, and the poor catalytic efficiency of KpcPA were identified as the rate-limiting bottlenecks. To this end, ribosome binding site regulation was employed to coordinate the enzyme molar ratio of EcCA:KpcPA:KpcPD at approximately 4:8:7 (the optimum ratio obtained in vitro), and volume scanning and hydrophobicity scanning were applied to increase KpcPA activity toward cadaverine from 15.89 ± 0.52 to 75.87 ± 1.51 U·mg^-1. Furthermore, the extracellular accumulation of 5-aminovalerate (5AVA) was considerably reduced by overexpressing gabP encoding the 5AVA importer. Combining these strategies into the engineered strain Glu-02, 77.62 g/L glutarate, the highest titer by E. coli to date, was produced from 100 g/L L-lysine in 42 h, with a yield and productivity of 0.78 g/g L-lysine and 1.85 g/L/h, respectively, at a 5-L scale. The results presented here provide a novel and potential enzymatic process at industrial-scale to produce glutarate from cheaper amino acids. KEY POINTS: • The bioconversion of l-lysine to glutarate using the Cad pathway was first achieved. • Enhancing the conversion efficiency of the Cad route maximizes glutarate in E. coli. • Achieving the highest titer of glutarate by E. coli to date.

New aspects of microbial vitamin K2 production by expanding the product spectrum

Vitamin K2 (menaquinone, MK) is an essential lipid-soluble vitamin with critical roles in blood coagulation and bone metabolism. Chemically, the term vitamin K2 encompasses a group of small molecules that contain a common naphthoquinone head group and a polyisoprenyl side chain of variable length. Among them, menaquinone-7 (MK-7) is the most potent form. Here, the biosynthetic pathways of vitamin K2 and different types of MK produced by microorganisms are briefly introduced. Further, we provide a new aspect of MK-7 production, which shares a common naphthoquinone ring and polyisoprene biosynthesis pathway, by analyzing strategies for expanding the product spectrum. We review the findings of metabolic engineering strategies targeting the shikimate pathway, polyisoprene pathway, and menaquinone pathway, as well as membrane engineering, which provide comprehensive insights for enhancing the yield of MK-7. Finally, the current limitations and perspectives of microbial menaquinone production are also discussed. This article provides in-depth information on metabolic engineering strategies for vitamin K2 production by expanding the product spectrum.

Development of antisense RNA-mediated quantifiable inhibition for metabolic regulation

Trans-regulating elements such as noncoding RNAs are crucial in modifying cells, and has shown broad application in synthetic biology, metabolic engineering and RNA therapies. Although effective, titration of the regulatory levels of such elements is less explored. Encouraged by the need of fine-tuning cellular functions, we studied key parameters of the antisense RNA design including oligonucleotide length, targeting region and relative dosage to achieve differentiated inhibition. We determined a 30-nucleotide configuration that renders efficient and robust inhibition. We found that by targeting the core RBS region proportionally, quantifiable inhibition levels can be rationally obtained. A mathematic model was established accordingly with refined energy terms and successfully validated by depicting the inhibition levels for genomic targets. Additionally, we applied this fine-tuning approach for 4-hydroxycoumarin biosynthesis by simultaneous and quantifiable knockdown of multiple targets, resulting in a 3.58-fold increase in titer of the engineered strain comparing to that of the non-regulated. We believe the developed tool is broadly compatible and provides an extra layer of control in modifying living systems.

•

Achieved quantifiable asRNA inhibition by varying core RBS coverage.

•

Developed and validated a mathematical model for quantifiable inhibition.

•

Improved 4-hydroxycoumarin biosynthesis by 3.58 folds with multiplexed inhibition.

Production of salicylic acid; a potent pharmaceutically active agent and its future prospects

Salicylic acid is one of the potent pharmaceutical organic acids that have various applications in the medical field. It acts as a plant hormone and helps in plant's growth & defence against pathogens. Beyond its numerous functions in plants, SA has great pharmaceutical importance since it acts as an intermediate for the synthesis of various drugs and dyes e.g. aspirin. At the industrial scale, chemical methods are used for the synthesis of SA but presently, several other sources are available that have the capability to alternate the chemical process which will be a step forward toward green synthesis. Aim of this paper is to provide comprehensive knowledge of SA production and its biological application.

Extending the shikimate pathway for microbial production of maleate from glycerol in engineered Escherichia coli

Maleate is one of the most important unsaturated four-carbon dicarboxylic acids. It serves as an attractive building block in cosmetic, polymer, and pharmaceutical industries. Currently, industrial production of maleate relies mainly on chemical synthesis using benzene or butane as the starting materials under high temperature, which suffers from strict reaction conditions and low product yield. Here, we propose a novel biosynthetic pathway for maleate production in engineered Escherichia coli. We screened a superior salicylate 5-hydroxylase that can catalyze hydroxylation of salicylate into gentisate with high conversion rate. Then, introduction of salicylate biosynthetic pathway and gentisate ring cleavage pathway allowed the synthesis of maleate from glycerol. Further optimizations including enhancement of precursors supply, disruption of competing pathways, and construction of a pyruvate recycling system, boosted maleate titer to 2.4 ± 0.1 g/L in shake flask experiments. Subsequent scale-up biosynthesis of maleate in a 3-L bioreactor under fed-batch culture conditions enabled the production of 14.5 g/L of maleate, indicating a 268-fold improvement compared with the titer generated by the wildtype E. coli strain carrying the entire maleate biosynthetic pathway. This study provided a promising microbial platform for industrial level synthesis of maleate, and demonstrated the highest titer of maleate production in microorganisms so far.

Constructing Microbial Hosts for the Production of Benzoheterocyclic Derivatives

Natural products containing benzoheterocyclic skeletons are widely found in plants and exhibit various pharmacological activities. To address the current limited availability of these compounds, we herein demonstrate the production of benzopyran, furanocoumarins, and pyranocoumarins in Streptomyces xiamenensis by employing prenyltransferases and two substrate-promiscuous enzymes, XimD and XimE. To avoid the degradation in S. xiamenensis, furanocoumarins and pyranocoumarins were also successfully produced in Escherichia coli. The production of linear furanocoumarins (marmesin) and angular pyranocoumarins (decursinol) reached 3.6 and 3.7 mg/L in shake flasks, respectively. To the best of our knowledge, this is the first report of the microbial production of the plant metabolites furanocoumarins and pyranocoumarins. Our study complements the missing link in the biosynthesis of pyranocoumarins by leveraging the catalytic promiscuity of microbial enzymes.

Engineering the oleaginous yeast Yarrowia lipolytica for high-level resveratrol production

Resveratrol is a plant secondary metabolite with multiple health-beneficial properties. Microbial production of resveratrol in model microorganisms requires extensive engineering to reach commercially viable levels. Here, we explored the potential of the non-conventional yeast Yarrowia lipolytica to produce resveratrol and several other shikimate pathway-derived metabolites (p-coumaric acid, cis,cis-muconic acid, and salicylic acid). The Y. lipolytica strain expressing a heterologous pathway produced 52.1 ± 1.2 mg/L resveratrol in a small-scale cultivation. The titer increased to 409.0 ± 1.2 mg/L when the strain was further engineered with feedback-insensitive alleles of the key genes in the shikimate pathway and with five additional copies of the heterologous biosynthetic genes. In controlled fed-batch bioreactor, the strain produced 12.4 ± 0.3 g/L resveratrol, the highest reported titer to date for de novo resveratrol production, with a yield on glucose of 54.4 ± 1.6 mg/g and a productivity of 0.14 ± 0.01 g/L/h. The study showed that Y. lipolytica is an attractive host organism for the production of resveratrol and possibly other shikimate-pathway derived metabolites.

•

Oleaginous yeast Y. lipolytica was engineered for production of aromatic compounds.

•

High resveratrol production required increased activities of Aro4p and Aro7p.

•

Multiple integration of resveratrol biosynthetic genes improved production.

•

Fed-batch fermentation enabled de novo production of 12.4 g/L resveratrol.

Isoprene: A Promising Coupling Partner in C–H Functionalizations

Five-carbon dimethylallyl units, such as prenyl and reverse-prenyl, are widely distributed in natural indole alkaloids and terpenoids. In conventional methodologies, these valuable motifs are often derived from substrates bearing leaving groups, but these processes are accompanied by the generation of stoichiometric amounts of by-products. From an economical and environmental point of view, the basic industrial feedstock isoprene is an ideal alternative precursor. However, given that electronically unbiased isoprene might undergo six possible addition modes in the coupling reactions, it is difficult to control the selectivity. This article summarizes the strategies we have developed to achieve regioselective C–H functionalizations of isoprene under transition-metal and acid catalysis.

1 Introduction

2 Catalytic Coupling of Indoles with Isoprene

3 Catalytic Coupling of Formaldehyde, Arenes and Isoprene

4 Catalytic Coupling of 4-Hydroxycoumarins with Isoprene

5 Catalytic Coupling of Cyclic 1,3-Diketones with Isoprene

6 Conclusion and Outlook

Bioprocess Optimization for the Production of Aromatic Compounds With Metabolically Engineered Hosts: Recent Developments and Future Challenges

The most common route to produce aromatic chemicals - organic compounds containing at least one benzene ring in their structure - is chemical synthesis. These processes, usually starting from an extracted fossil oil molecule such as benzene, toluene, or xylene, are highly environmentally unfriendly due to the use of non-renewable raw materials, high energy consumption and the usual production of toxic by-products. An alternative way to produce aromatic compounds is extraction from plants. These extractions typically have a low yield and a high purification cost. This motivates the search for alternative platforms to produce aromatic compounds through low-cost and environmentally friendly processes. Microorganisms are able to synthesize aromatic amino acids through the shikimate pathway. The construction of microbial cell factories able to produce the desired molecule from renewable feedstock becomes a promising alternative. This review article focuses on the recent advances in microbial production of aromatic products, with a special emphasis on metabolic engineering strategies, as well as bioprocess optimization. The recent combination of these two techniques has resulted in the development of several alternative processes to produce phenylpropanoids, aromatic alcohols, phenolic aldehydes, and others. Chemical species that were unavailable for human consumption due to the high cost and/or high environmental impact of their production, have now become accessible.

Wastewater-borne exposure of limnic fish to anticoagulant rodenticides

The recent emergence of second-generation anticoagulant rodenticides (AR) in the aquatic environment emphasizes the relevance and impact of aquatic exposure pathways during rodent control. Pest control in municipal sewer systems of urban and suburban areas is thought to be an important emission pathway for AR to reach wastewater and municipal wastewater treatment plants (WWTP), respectively. To circumstantiate that AR will enter streams via effluent discharges and bioaccumulate in aquatic organisms despite very low predicted environmental emissions, we conducted a retrospective biological monitoring of fish tissue samples from different WWTP fish monitoring ponds exclusively fed by municipal effluents in Bavaria, Germany. At the same time, information about rodent control in associated sewer systems was collected by telephone survey to assess relationships between sewer baiting and rodenticide residues in fish. In addition, mussel and fish tissue samples from several Bavarian surface waters with different effluent impact were analyzed to evaluate the prevalence of anticoagulants in indigenous aquatic organisms. Hepatic AR residues were detected at 12 out of 25 WWTP sampling sites in the low μg/kg range, thereof six sites with one or more second-generation AR (i.e., brodifacoum, difenacoum, bromadiolone). 14 of 18 surveyed sites confirmed sewer baiting with AR and detected hepatic residues matched the reported active ingredients used for sewer baiting at six sites. Furthermore, second-generation AR were detected in more than 80% of fish liver samples from investigated Bavarian streams. Highest total hepatic AR concentrations in these fish were 9.1 and 8.5 μg/kg wet weight, respectively and were observed at two riverine sampling sites characterized by close proximity to upstream WWTP outfalls. No anticoagulant residues were found in fish liver samples from two lakes without known influences of effluent discharges. The findings of our study clearly show incomplete removal of anticoagulants during conventional wastewater treatment and confirm exposure of aquatic organisms via municipal effluents. Based on the demonstrated temporal and spatial coherence between sewer baiting and hepatic AR residues in effluent-exposed fish, sewer baiting in combined sewer systems contributes to the release of active ingredients into the aquatic environment.

How structural subtleties lead to molecular diversity for the type III polyketide synthases

Type III polyketide synthases (PKSs) produce an incredibly diverse group of plant specialized metabolites with medical importance despite their structural simplicity compared with the modular type I and II PKS systems. The type III PKSs use homodimeric proteins to construct the molecular scaffolds of plant polyketides by iterative condensations of starter and extender CoA thioesters. Ever since the structure of chalcone synthase (CHS) was disclosed in 1999, crystallographic and mutational studies of the type III PKSs have explored the intimate structural features of these enzyme reactions, revealing that seemingly minor alterations in the active site can drastically change the catalytic functions and product profiles. New structures described in this review further build on this knowledge, elucidating the detailed catalytic mechanism of enzymes that make curcuminoids, use extender substrates without the canonical CoA activator, and use noncanonical starter substrates, among others. These insights have been critical in identifying structural features that can serve as a platform for enzyme engineering via structure-guided and precursor-directed engineered biosynthesis of plant polyketides. In addition, we describe the unique properties of the recently discovered "second-generation" type III PKSs that catalyzes the one-pot formation of complex molecular scaffolds from three distinct CoA thioesters or from "CoA-free" substrates, which are also providing exciting new opportunities for synthetic biology approaches. Finally, we consider post-type III PKS tailoring enzymes, which can also serve as useful tools for combinatorial biosynthesis of further unnatural novel molecules. Recent progress in the field has led to an exciting time of understanding and manipulating these fascinating enzymes.

Engineering a Bifunctional Phr60-Rap60-Spo0A Quorum-Sensing Molecular Switch for Dynamic Fine-Tuning of Menaquinone-7 Synthesis in Bacillus subtilis

Quorum sensing (QS)-based dynamic regulation has been widely used as basic tool for fine-tuning gene expression in response to cell density changes without adding expensive inducers. However, most reported QS systems primarily relied on down-regulation rather than up-regulation of gene expression, significantly limiting its potential as a molecular switch to control metabolic flux. To solve this challenge, we developed a bifunctional and modular Phr60-Rap60-Spo0A QS system, based on two native promoters, P_abrB (down-regulation by Spo0A-P) and P_spoiiA (up-regulation by Spo0A-P). We constructed a library of promoters with different capacities to implement down-regulation and up-regulation by changing the location, number, and sequences of the binding sites for Spo0A-P. The QS system can dynamically balance the relationship between efficient synthesis of the target product and cell growth. Finally, we validated the usefulness of this strategy by dynamic control of menaquinone-7 (MK-7) synthesis in Bacillus subtilis 168, a model Gram-positive bacterium, with the bifunctional Phr60-Rap60-Spo0A quorum sensing system. Our dynamic pathway regulation led to a 40-fold improvement of MK-7 production from 9 to 360 mg/L in shake flasks and 200 mg/L in 15-L bioreactor. Taken together, our bilayer QS system has been successfully integrated with biocatalytic functions to achieve dynamic pathway regulation in B. subtilis 168, which may be extended for use in other microbes to fine-tune gene expression and improve metabolites production.

Synthesis of Three Bioactive Aromatic Compounds by Introducing Polyketide Synthase Genes into Engineered Escherichia coli

Intermediates in aromatic amino acid biosynthesis can serve as substrates for the synthesis of bioactive compounds. In this study we used two intermediates in the shikimate pathway of Escherichia coli, chorismate and anthranilate, to synthesize three bioactive compounds: 4-hydroxycoumarin (4-HC), 2,4-dihydroxyquinoline (DHQ), and 4-hydroxy-1-methyl-2(1H)-quinolone (NMQ). We introduced genes for the synthesis of salicylic acid from chorismate to supply the substrate for 4-HC and the gene encoding N-methyltransferase for the synthesis of N-methylanthranilate from anthranilate. Polyketide synthases and coenzyme (Co)A ligases were tested to determine the optimal combination of genes for the synthesis of each compound. We also tested several constructs and identified the best one for increasing levels of endogenous substrates for chorismate, anthranilate, and malonyl-CoA. With the use of these strategies, 255.4 mg/L 4-HC, 753.7 mg/L DHQ, and 17.5 mg/L NMQ were synthesized. This work provides a basis for the synthesis of diverse coumarin and quinoline derivatives with potential medical applications.

Harnessing biocompatible chemistry for developing improved and novel microbial cell factories

White biotechnology relies on the sophisticated chemical machinery inside living cells for producing a broad range of useful compounds in a sustainable and environmentally friendly way. However, despite the impressive repertoire of compounds that can be generated using white biotechnology, this approach cannot currently fully replace traditional chemical production, often relying on petroleum as a raw material. One challenge is the limited number of chemical transformations taking place in living organisms. Biocompatible chemistry, that is non‐enzymatic chemical reactions taking place under mild conditions compatible with living organisms, could provide a solution. Biocompatible chemistry is not a novel invention, and has since long been used by living organisms. Examples include Fenton chemistry, used by microorganisms for degrading plant materials, and manganese or ketoacids dependent chemistry used for detoxifying reactive oxygen species. However, harnessing biocompatible chemistry for expanding the chemical repertoire of living cells is a relatively novel approach within white biotechnology, and it could potentially be used for producing valuable compounds which living organisms otherwise are not able to generate. In this mini review, we discuss such applications of biocompatible chemistry, and clarify the potential that lies in using biocompatible chemistry in conjunction with metabolically engineered cell factories for cheap substrate utilization, improved cell physiology, efficient pathway construction and novel chemicals production.