Green chemical and biological synthesis of cadaverine: recent development and challenges

A comprehensive review on the recent advances for 5-aminolevulinic acid production by the engineered bacteria

5-Aminolevulinic acid (5-ALA) is a non-proteinogenic amino acid essential for synthesizing tetrapyrrole compounds, including heme, chlorophyll, cytochrome, and vitamin B12. As a plant growth regulator, 5-ALA is extensively used in agriculture to enhance crop yield and quality. The complexity and low yield of chemical synthesis methods have led to significant interest in the microbial synthesis of 5-ALA. Advanced strategies, including the: enhancement of precursor and cofactor supply, compartmentalization of key enzymes, product transporters engineering, by-product formation reduction, and biosensor-based dynamic regulation, have been implemented in bacteria for 5-ALA production, significantly advancing its industrialization. This article offers a comprehensive review of recent developments in 5-ALA production using engineered bacteria and presents new insights to propel the field forward.

Fine-Tuning Pyridoxal 5'-Phosphate Synthesis in Escherichia coli for Cadaverine Production in Minimal Culture Media

Cadaverine is a critical C5 monomer for the production of polyamides. Pyridoxal 5'-phosphate (PLP), as a crucial cofactor for the key enzyme lysine decarboxylase in the cadaverine biosynthesis pathway, has seen a persistent shortage, leading to limitations in cadaverine production. To address this issue, a dual-pathway strategy was implemented, synergistically enhancing both endogenous and heterologous PLP synthesis modules and resulting in improved PLP synthesis. Subsequently, a growth-stage-dependent molecular switch was introduced to balance the precursor competition between PLP synthesis and cell growth. Additionally, a PLP sensor-based negative feedback circuit was constructed by integrating a newly identified PLP-responsive promoter PygjH and an arabinose-regulated system, dynamically regulating the expression of the PLP synthetic genes and preventing excessive intracellular PLP accumulation. The optimal strain, L18, cultivated in the minimal medium AM1, demonstrated cadaverine production with a titer, yield, and productivity of 64.03 g/L, 0.23 g/g glucose, and 1.33 g/L/h, respectively. This represents the highest titer reported to date in engineered Escherichia coli by fed-batch fermentation in a minimal medium.

Histamine H4 receptor and TRPV1 mediate itch induced by cadaverine, a metabolite of the microbiome

Cadaverine is an endogenous metabolite produced by the gut microbiome with various activity in physiological and pathological conditions. However, whether cadaverine regulates pain or itch remains unclear. In this study, we first found that cadaverine may bind to histamine 4 receptor (H4R) with higher docking energy score using molecular docking simulations, suggesting cadaverine may act as an endogenous ligand for H4R. We subsequently found intradermal injection of cadaverine into the nape or cheek of mice induces a dose-dependent scratching response in mice, which was suppressed by a selective H4R antagonist JNJ-7777120, transient receptor potential vanilloid 1 (TRPV1) antagonist capsazepine and PLC inhibitor U73122, but not H1R antagonist or TRPA1 antagonist or TRPV4 antagonist. Consistently, cadaverine-induced itch was abolished in Trpv1-/- but not Trpa1-/- mice. Pharmacological analysis indicated that mast cells and opioid receptors were also involved in cadaverine-induced itch in mice. scRNA-Seq data analysis showed that H4R and TRPV1 are mainly co-expressed on NP2, NP3 and PEP1 DRG neurons. Calcium imaging analysis showed that cadaverine perfusion enhanced calcium influx in the dissociated dorsal root ganglion (DRG) neurons, which was suppressed by JNJ-7777120 and capsazepine, as well as in the DRG neurons from Trpv1-/- mice. Patch-clamp recordings found that cadaverine perfusion significantly increased the excitability of small diameter DRG neurons, and JNJ-7777120 abolished this effect, indicating involvement of H4R. Together, these results provide evidences that cadaverine is a novel endogenous pruritogens, which activates H4R/TRPV1 signaling pathways in the primary sensory neurons.

Bio-based monomers for amide-containing sustainable polymers

The field of sustainable polymers from renewable feedstocks is a fast-reviving field after the decades-long domination of petroleum-based polymers. Amide-containing polymers exhibit a wide range of properties depending on the type of amide (primary, secondary, and tertiary), amide density, and other molecular structural parameters (co-existing groups, molecular weight, and topology). Engineering amide groups into sustainable polymers via the "monomer approach" is an industrially proven strategy, while bio-based monomers are of enormous importance to bridge the gap between renewable sources and amide-containing sustainable polymers (AmSPs). This feature article aims at conceptualizing the monomer-design philosophy behind most of the reported AmSPs and is organized by discussing di-functional monomers for step-growth polymerization, cyclic monomers for ring-opening polymerization and amide-containing monomers for chain-growth polymerization. We also give a perspective on AmSPs with respect to monomer design and performance enhancement.

A direct enzymatic evaluation platform (DEEP) to fine-tuning pyridoxal 5'-phosphate-dependent proteins for cadaverine production

Pyridoxal 5'-phosphate (pyridoxal phosphate, PLP) is an essential cofactor for multiple enzymatic reactions in industry. However, cofactor engineering based on PLP regeneration and related to the performance of enzymes in chemical production has rarely been discussed. First, we found that MG1655 strain was sensitive to nitrogen source and relied on different amino acids, thus the biomass was significantly reduced when PLP excess in the medium. Then, the six KEIO collection strains were applied to find out the prominent gene in deoxyxylulose-5-phosphate (DXP) pathway, where pdxB was superior in controlling cell growth. Therefore, the clustered regularly interspaced short palindromic repeats interference (CRISPRi) targeted on pdxB in MG1655 was employed to establish a novel direct enzymatic evaluation platform (DEEP) as a high-throughput tool and obtained the optimal modules for incorporating of PLP to enhance the biomass and activity of PLP-dependent enzymes simultaneously. As a result, the biomass has increased by 55% using P_lacI promoter driven pyridoxine 5'-phosphate oxidase (PdxH) with a trace amount of precursor. When the strains incorporated DEEP and lysine decarboxylase (CadA), the cadaverine productivity was increased 32% due to the higher expression of CadA. DEEP is not only feasible for high-throughput screening of the best chassis for PLP engineering but also practical in fine-tuning the quantity and quality of enzymes.

Prospecting Microbial Genomes for Biomolecules and Their Applications

Bioactive molecules of microbial origin are finding increasing biotechnological applications. Their sources range from the terrestrial, marine, and endophytic to the human microbiome. These biomolecules have unique chemical structures and related groups, which enable them to improve the efficiency of the bioprocesses. This review focuses on the applications of biomolecules in bioremediation, agriculture, food, pharmaceutical industries, and human health.

Engineered Halomonas spp. for production of l-Lysine and cadaverine

Cadaverine, a derivative of l-lysine, has been used as a monomer for the synthesis of bio-based nylon-5,6. This study engineered Halomonas bluephagenesis TD1.0 by blocking the feedback inhibition, overexpressing the key l-lysine synthesis genes, strengthening the l-lysine export system and increasing the supply of oxaloacetate for production of l-lysine in the supernatant and PHB in the cells. Subsequently, cadaverine biosynthetic pathway was constructed in H. campaniensis LC-9 to improve the efficiency of de novo cadaverine biosynthesis which combines l-lysine producing H. bluephagenesis TDL8-68-259 and cadaverine producing H. campaniensis LC-9-ldcC-lysP. When H. campaniensis LC-9-ldcC-lysP was used as a whole cell catalysis for cadaverine production, the conversion efficiency of l-lysine to cadaverine reached 100% in the presence of 0.05% Triton X-100 for cell membrane permeability enhancement, resulting in 118 g L^-1 cadaverine formed in the fermentor. Thus, Halomonas spp. have been successfully constructed for l-lysine and cadaverine production.

From Enzyme to Preparative Cascade Reactions with Immobilized Enzymes: Tuning Fe(II)/α-Ketoglutarate-Dependent Lysine Hydroxylases for Application in Biotransformations

Fe(II)/α-ketoglutarate-dependent dioxygenases (KDOs) catalyze a broad range of selective C–H oxidation reactions. However, the difficult production of KDOs in recombinant E. coli strains and their instability in purified form have so far limited their application in preparative biotransformations. Here, we investigated the immobilization of three KDOs (CaKDO, CpKDO, FjKDO) that catalyze the stereoselective hydroxylation of the L-lysine side chain using two one-step immobilization techniques (HaloTag®, EziG™). The HaloTag®-based immobilisates reached the best results with respect to residual activity and stability. In preparative lab-scale experiments, we achieved product titers of 16 g L−1 (3S)-hydroxy-L-lysine (CaKDO) and (4R)-hydroxy-L-lysine (FjKDO), respectively, starting from 100 mM L-lysine. Using a HaloTag®-immobilized lysine decarboxylase from Selenomonas ruminantium (SrLDC), the (3S)-hydroxy-L-lysine from the CaKDO-catalyzed reaction was successfully converted to (2S)-hydroxy-cadaverine without intermediate product purification, yielding a product titer of 11.6 g L−1 in a 15 mL consecutive batch reaction. We propose that covalent in situ immobilization is an appropriate tool to access the preparative potential of many other KDOs.

Production of Cadaverine in Recombinant Corynebacterium glutamicum Overexpressing Lysine Decarboxylase (ldcC) and Response Regulator dr1558

In this study, the response regulator DR1558 from Deinococcus radiodurans was overexpressed in recombinant Corynebacterium glutamicum with lysine decarboxylase (ldcC). The recombinant C. glutamicum strain overexpressing dr1558 and ldcC produced 5.9 g/L of cadaverine by flask cultivation, whereas the control strain overexpressing only ldcC produced 4.5 g/L of cadaverine. To investigate the mechanism underlying the effect of DR1558, the expression levels of genes related to central metabolism and lysine-biosynthesis were analyzed by quantitative-real time polymerase chain reaction. The results showed that phosphoenolpyruvate carboxykinase (pck) was downregulated, and pyruvate kinase (pyk) and other lysine biosynthesis genes were upregulated. Furthermore, in fed-batch fermentation, C. glutamicum coexpressing dr1558 produced 25.14 g/L of cadaverine, a 1.25-fold increase in concentration relative to the control. These results suggested that the heterologous expression of dr1558 may improve the production of biorefinery products by recombinant C. glutamicum.