The role of acyl-CoA thioesterase ACOT8I in mediating intracellular lipid metabolism in oleaginous fungus <Emphasis Type="Italic">Mortierella alpina</Emphasis>

Thioesterases (TEs) play an essential role in the metabolism of fatty acids (FAs). To explore the role of TEs in mediating intracellular lipid metabolism in the oleaginous fungus Mortierella alpina, the acyl-CoA thioesterase ACOT8I was overexpressed. The contents of total fatty acids (TFAs) were the same in the recombinant strains as in the wild-type M. alpina, whilst the production of free fatty acids (FFAs) was enhanced from about 0.9% (wild-type) to 2.8% (recombinant), a roughly threefold increase. Linoleic acid content in FFA form constituted about 9% of the TFAs in the FFA fraction in the recombinant strains but only about 1.3% in the wild-type M. alpina. The gamma-linolenic acid and arachidonic acid contents in FFA form accounted for about 4 and 25%, respectively, of the TFAs in the FFA fraction in the recombinant strains, whilst neither of them in FFA form were detected in the wild-type M. alpina. Overexpression of the TE ACOT8I in the oleaginous fungus M. alpina reinforced the flux from acyl-CoAs to FFAs, improved the production of FFAs and tailored the FA profiles of the lipid species.     

Boosting fatty acid synthesis in <Emphasis Type="Italic">Rhodococcus opacus</Emphasis> PD630 by overexpression of autologous thioesterases

Objectives

To explore the role of thioesterases in Rhodococcus opacus PD630 by endogenously overexpression in this bacteria for increased lipid production.

Results

Overexpression of four thioesterases from R. opacus PD630 in E. coli led to a 2- to 8-fold increase in C16:1 and C18:1 fatty acids while, when overexpressed in R. opacus PD630, only two recombinants had significant effect on the quantities and compositions of total fatty acid. The contents of total fatty acids (FAs) in two recombinants, pJTE2 (OPAG_00508 thioesterase) and pJTE4 (WP_012687673.1 thioesterase), were 400–460 mg/g (CDW) which is 1.5 times of wild-type strain PD630 (300-350 mg/g CDW), and 20–30 % (w/w) more than that of the control strain PDpJAM2 (330-370 mg/g CDW). The contents of 17:1 and 18:1 fatty acids increased by about 27 and 35 %, respectively, in pJTE2 and by 35 and 20 %, respectively, in pJTE4 compared with the control strain.

Conclusions

The engineered strains showed improved production of lipid (as total fatty acids), and could also tailor the composition of the fatty acid profile when cultured in mineral salts medium using glucose as sole carbon source.

     

Cytoplasmic expression of a thermostable invertase from <Emphasis Type="Italic">Thermotoga maritima</Emphasis> in <Emphasis Type="Italic">Lactococcus lactis</Emphasis>

Objectives

To evaluate the secretory and cytoplasmic expression of a thermostable Thermogata maritima invertase in Lactococcus lactis.

Results

The thermostable invertase from T. maritima was cloned with and without the USP45 secretory peptide into the pNZ8148 vector for nisin-inducible expression in L. lactis. The introduction of an USP45 secretion peptide at the N-terminal of the enzyme led to a loss of protein solubility. Computational homology modeling and hydrophobicity studies indicated that the USP45 peptide exposes a stretch of hydrophobic amino acids on the protein surface resulting in lower solubility. Removal of the USP45 secretion peptide allowed a soluble and functional invertase to be expressed intracellularly in L. lactis. Immobilized metal affinity chromatography purification of the cell lysate with nickel-NTA gave a single protein band on SDS-PAGE, while E. coli-expressed invertase consistently co-purified with an additional band. The yields of the purified invertase from E. coli and L. lactis were 14.1 and 6.3 mg/l respectively.

Conclusions

Invertase can be expressed in L. lactis and purified in a functional form. L. lactis is a suitable host for the production of food-grade invertase for use in the food and biotechnology industries.

     

Dual-species biofilm of <Emphasis Type="Italic">Listeria monocytogenes</Emphasis> and <Emphasis Type="Italic">Escherichia coli</Emphasis> on stainless steel surface

Listeria monocytogenes is a Gram-positive bacterium commonly associated with foodborne diseases. Due its ability to survive under adverse environmental conditions and to form biofilm, this bacterium is a major concern for the food industry, since it can compromise sanitation procedures and increase the risk of post-processing contamination. Little is known about the interaction between L. monocytogenes and Gram-negative bacteria on biofilm formation. Thus, in order to evaluate this interaction, Escherichia coli and L. monocytogenes were tested for their ability to form biofilms together or in monoculture. We also aimed to evaluate the ability of L. monocytogenes 1/2a and its isogenic mutant strain (ΔprfA ΔsigB) to form biofilm in the presence of E. coli. We assessed the importance of the virulence regulators, PrfA and σ^B, in this process since they are involved in many aspects of L. monocytogenes pathogenicity. Biofilm formation was assessed using stainless steel AISI 304 #4 slides immersed into brain heart infusion broth, reconstituted powder milk and E. coli preconditioned medium at 25 °C. Our results indicated that a higher amount of biofilm was formed by the wild type strain of L. monocytogenes than by its isogenic mutant, indicating that prfA and sigB are important for biofilm development, especially maturation under our experimental conditions. The presence of E. coli or its metabolites in preconditioned medium did not influence biofilm formation by L. monocytogenes. Our results confirm the possibility of concomitant biofilm formation by L. monocytogenes and E. coli, two bacteria of major significance in the food industry.     

<Emphasis Type="Italic">In vitro</Emphasis> Blastogenesis inhibited by <Emphasis Type="Italic">Erwinia carotovora</Emphasis><Emphasis Type="SmallCaps">L</Emphasis>-Asparaginase

Escherichia coliL-asparaginase, an antileukaemic agent in man¹, inhibits in vitro mitogen or antigen-induced blastogenesis in man^2,3 and in animals (M. Bennett, E. G. Mayhew and T. Han, unpublished data) and suppresses bone-marrow derived antibody precursor cells in the mouse⁴. We now report that another L-asparaginase preparation—from Erwinia carotovora—also possesses antileukaemic activity^5,6 and has a more pronounced immunosuppressive effect on in vitro blastogenesis than the E. coli enzyme.     

Phosphoenolpyruvate-supply module in <Emphasis Type="Italic">Escherichia coli</Emphasis> improves <Emphasis Type="Italic">N</Emphasis>-acetyl-<Emphasis Type="SmallCaps">d</Emphasis>-neuraminic acid biocatalysis

Objectives

N-Acetyl-d-neuraminic acid (Neu5Ac) is often synthesized from exogenous N-acetylglucosamine (GlcNAc) and excess pyruvate. We have previously constructed a recombinant Escherichia coli strain for Neu5Ac production using GlcNAc and intracellular phosphoenolpyruvate (PEP) as substrates (Zhu et al. Biotechnol Lett 38:1–9, 2016).

Results

PEP synthesis-related genes, pck and ppsA, were overexpressed within different modes to construct PEP-supply modules, and their effects on Neu5Ac production were investigated. All the PEP-supply modules enhanced Neu5Ac production. For the best module, pCDF-pck-ppsA increased Neu5Ac production to 8.6 ± 0.15 g l^?1, compared with 3.6 ± 0.15 g l^?1 of the original strain. Neu5Ac production was further increased to 15 ± 0.33 g l^?1 in a 1 l fermenter.

Conclusions

The PEP-supply module can improve the intracellular PEP supply and enhance Neu5Ac production, which benefited industrial Neu5Ac production.

     

Conjugative plasmid transfer from <Emphasis Type="Italic">Escherichia coli</Emphasis> is a versatile approach for genetic transformation of thermophilic <Emphasis Type="Italic">Bacillus</Emphasis> and <Emphasis Type="Italic">Geobacillus</Emphasis> species

We previously demonstrated efficient transformation of the thermophile Geobacillus kaustophilus HTA426 using conjugative plasmid transfer from Escherichia coli BR408. To evaluate the versatility of this approach to thermophile transformation, this study examined genetic transformation of various thermophilic Bacillus and Geobacillus spp. using conjugative plasmid transfer from E. coli strains. E. coli BR408 successfully transferred the E. coli–Geobacillus shuttle plasmid pUCG18T to 16 of 18 thermophiles with transformation efficiencies between 4.1 × 10^?7 and 3.8 × 10^?2/recipient. Other E. coli strains that are different from E. coli BR408 in intracellular DNA methylation also generated transformants from 9 to 15 of the 18 thermophiles, including one that E. coli BR408 could not transform, although the transformation efficiencies of these strains were generally lower than those of E. coli BR408. The conjugation was performed by simple incubation of an E. coli donor and a thermophile recipient without optimization of experimental conditions. Moreover, thermophile transformants were distinguished from abundant E. coli donor only by high temperature incubation. These observations suggest that conjugative plasmid transfer, particularly using E. coli BR408, is a facile and versatile approach for plasmid introduction into thermophilic Bacillus and Geobacillus spp., and potentially a variety of other thermophiles.     

Engineering a <Emphasis Type="Italic">Streptomyces coelicolor</Emphasis> biosynthesis pathway into <Emphasis Type="Italic">Escherichia coli</Emphasis> for high yield triglyceride production

Background

Microbial lipid production represents a potential alternative feedstock for the biofuel and oleochemical industries. Since Escherichia coli exhibits many genetic, technical, and biotechnological advantages over native oleaginous bacteria, we aimed to construct a metabolically engineered E. coli strain capable of accumulating high levels of triacylglycerol (TAG) and evaluate its neutral lipid productivity during high cell density fed-batch fermentations.

Results

The Streptomyces coelicolor TAG biosynthesis pathway, defined by the acyl-CoA:diacylglycerol acyltransferase (DGAT) Sco0958 and the phosphatidic acid phosphatase (PAP) Lppβ, was successfully reconstructed in an E. coli diacylglycerol kinase (dgkA) mutant strain. TAG production in this genetic background was optimized by increasing the levels of the TAG precursors, diacylglycerol and long-chain acyl-CoAs. For this we carried out a series of stepwise optimizations of the chassis by 1) fine-tuning the expression of the heterologous SCO0958 and lpp β genes, 2) overexpression of the S. coelicolor acetyl-CoA carboxylase complex, and 3) mutation of fadE, the gene encoding for the acyl-CoA dehydrogenase that catalyzes the first step of the β-oxidation cycle in E. coli. The best producing strain, MPS13/pET28-0958-ACC/pBAD-LPPβ rendered a cellular content of 4.85% cell dry weight (CDW) TAG in batch cultivation. Process optimization of fed-batch fermentation in a 1-L stirred-tank bioreactor resulted in cultures with an OD_600nm of 80 and a product titer of 722.1 mg TAG L^-1 at the end of the process.

Conclusions

This study represents the highest reported fed-batch productivity of TAG reached by a model non-oleaginous bacterium. The organism used as a platform was an E. coli BL21 derivative strain containing a deletion in the dgkA gene and containing the TAG biosynthesis genes from S. coelicolor. The genetic studies carried out with this strain indicate that diacylglycerol (DAG) availability appears to be one of the main limiting factors to achieve higher yields of the storage compound. Therefore, in order to develop a competitive process for neutral lipid production in E. coli, it is still necessary to better understand the native regulation of the carbon flow metabolism of this organism, and in particular, to improve the levels of DAG biosynthesis.

     

Cloning of <Emphasis Type="Italic">phaCAB</Emphasis> genes from thermophilic <Emphasis Type="Italic">Caldimonas manganoxidans</Emphasis> in <Emphasis Type="Italic">Escherichia coli</Emphasis> for poly(3-hydroxybutyrate) (PHB) production

PHB biosynthesis pathway, consisting of three open reading frames (ORFs) that encode for β-ketothiolase (phaA _Cma , 1179 bp), acetoacetyl-CoA reductase (phaB _Cma , 738 bp), and PHA synthase (phaC _Cma , 1694 bp), of Caldimonas manganoxidans was identified. The functions of PhaA, PhaB, and PhaC were demonstrated by successfully reconstructing PHB biosynthesis pathway of C. manganoxidans in Escherichia coli, where PHB production was confirmed by OD₆₀₀, gas chromatography, Nile blue stain, and transmission electron microscope (TEM). The protein sequence alignment of PHB synthases revealed that phaC _Cma shares at least 60% identity with those of class I PHB synthase. The effects of PhaA, PhaB, and PhaC expression levels on PHB production were investigated. While the overexpression of PhaB is found to be important in recombinant E. coli, performances of PHB production can be quantified as follows: PHB concentration of 16.8 ± 0.6 g/L, yield of 0.28 g/g glucose, content of 74%, productivity of 0.28 g/L/h, and Mw of 1.41 MDa.     

Deletion of <Emphasis Type="Italic">ldh</Emphasis>A and <Emphasis Type="Italic">ald</Emphasis>H genes in <Emphasis Type="Italic">Klebsiella</Emphasis><Emphasis Type="Italic">pneumoniae</Emphasis> to enhance 1,3-propanediol production

Objectives

To improve 1,3-propanediol (1,3-PD) production and reduce byproduct concentration during the fermentation of Klebsiella pneumonia.

Results

Klebsiella. pneumonia 2-1ΔldhA, K. pneumonia 2-1ΔaldH and K. pneumonia 2-1ΔldhAΔaldH mutant strains were obtained through deletion of the ldhA gene encoding lactate dehydrogenase required for lactate synthesis and the aldH gene encoding acetaldehyde dehydrogenase involved in the synthesis of ethanol. After fed-batch fermentation, the production of 1,3-PD from glycerol was enhanced and the concentrations of byproducts were reduced compared with the original strain K. pneumonia 2-1. The maximum yields of 1,3-PD were 85.7, 82.5 and 87.5 g/l in the respective mutant strains.

Conclusion

Deletion of either aldH or ldhA promoted 1,3-PD production in K. pneumonia.

     

Cloning of <Emphasis Type="Italic">rec</Emphasis>A gene of <Emphasis Type="Italic">Corynebacterium glutamicum</Emphasis> and phenotypic complementation of <Emphasis Type="Italic">Escherichia coli</Emphasis> recombinant deficient strain

Nucleotide and amino acid sequences of Corynebacterium glutamicum recA genes, from GenBank, were compared in silico. On the basis of the identity found between sequences, two degenerate primers were designed on the two sides of the deduced open reading frame (ORF) of the recA gene. PCR experiments, for amplifying the recA ORF region, were done. pGEM^®-T Easy vector was selected to be used for cloning PCR products. Then recA ORF was placed under the control of Escherichia coli hybrid trc promoter, in pKK388-1 vector. pKK388-1 vector, containing recA ORF, was transformed to E. coli DH5α ΔrecA (recombinant deficient strain), in an attempt to phenotypically complement it. Ultraviolet (u.v.) exposure experiments of the transformed and non-transformed E. coli DH5α ΔrecA cells revealed tolerance of transformed cells up to dose 0.24 J/cm², while non-transformed cells tolerated only up to dose 0.08 J/cm². It is concluded that phenotypic complementation of E. coli DH5α ΔrecA with recA ORF of C. glutamicum, could be achieved and RecA activity could be restored.     

<Emphasis Type="Italic">glyA</Emphasis> gene knock-out in <Emphasis Type="Italic">Escherichia coli</Emphasis> enhances L-serine production without glycine addition

In E. coli, glyA encodes for serine hydroxymethyltransferase (SHMT), which converts L-serine to glycine. When engineering L-serine-producing strains, it is therefore favorable to inactivate glyA to prevent L-serine degradation. However, most glyA knockout strains exhibit slow cell growth because of the resulting lack of glycine and C₁ units. To overcome this problem, we overexpressed the gcvTHP genes of the glycine cleavage system (GCV), to increase the C₁ supply before glyA was knocked out. Subsequently, the kbl and tdh genes were overexpressed to provide additional glycine via the L-threonine degradation pathway, thus restoring normal cell growth independent of glycine addition. Finally, the plasmid pPK10 was introduced to overexpress pgk, serA ^Δ197 , serC and serB, and the resulting strain E4G2 (pPK10) accumulated 266.3 mg/L of L-serine in a semi-defined medium without adding glycine, which was 3.18-fold higher than the production achieved by the control strain E3 (pPK10). This strategy can accordingly be applied to disrupt the L-serine degradation pathway in industrial production strains without causing negative side-effects, ultimately making L-serine production more efficient.     

Production of <Emphasis Type="Italic">trans</Emphasis>-10,<Emphasis Type="Italic">cis</Emphasis>-12-conjugated linoleic acid using permeabilized whole-cell biocatalyst of <Emphasis Type="Italic">Yarrowia lipolytica</Emphasis>

Objective

To improve the production of trans-10,cis-12-conjugated linoleic acid (t10,c12-CLA) from linoleic acid in recombinant Yarrowia lipolytica.

Results

Cells of the yeast were permeabilized by freeze/thawing. The optimal conditions for t10,c12-CLA production by the permeabilized cells were at 28 °C, pH 7, 200 rpm with 1.5 g sodium acetate l^?1, 100 g wet cells l^?1, and 25 g LA l^?1. Under these conditions, the permeabilized cells produced 15.6 g t10,c12-CLA l^?1 after 40 h, with a conversion yield of 62 %. The permeabilized cells could be used repeatedly for three cycles, with the t10,c12-CLA extracellular production remaining above 10 g l^?1.

Conclusion

Synthesis of t10,c12-CLA was achieved using a novel method, and the production reported in this work is the highest value reported to date.

     

Production of caffeoylmalic acid from glucose in engineered <Emphasis Type="Italic">Escherichia coli</Emphasis>

Objectives

To achieve biosynthesis of caffeoylmalic acid from glucose in engineered Escherichia coli.

Results

We constructed the biosynthetic pathway of caffeoylmalic acid in E. coli by co-expression of heterologous genes RgTAL, HpaBC, At4CL2 and HCT2. To enhance the production of caffeoylmalic acid, we optimized the tyrosine metabolic pathway of E. coli to increase the supply of the substrate caffeic acid. Consequently, an E. coli–E. coli co-culture system was used for the efficient production of caffeoylmalic acid. The final titer of caffeoylmalic acid reached 570.1 mg/L.

Conclusions

Microbial production of caffeoylmalic acid using glucose has application potential. In addition, microbial co-culture is an efficient tool for producing caffeic acid esters.

     

Enhancement of crystallinity of cellulose produced by <Emphasis Type="Italic">Escherichia coli</Emphasis> through heterologous expression of <Emphasis Type="Italic">bcsD</Emphasis> gene from <Emphasis Type="Italic">Gluconacetobacter xylinus</Emphasis>

Objectives

To evaluate the crystallinity index of the cellulose produced by Escherichia coli Nissle 1917 after heterologous expression of the cellulose synthase subunit D (bcsD) gene of Gluconacetobacter xylinus BPR2001.

Results

The bcsD gene of G. xylinus BPR2001 was expressed in E. coli and its protein product was visualized using SDS-PAGE. FTIR analysis showed that the crystallinity index of the cellulose produced by the recombinants was 0.84, which is 17% more than that of the wild type strain. The increased crystallinity index was also confirmed by X-ray diffraction analysis. The cellulose content was not changed significantly after over-expressing the bcsD.

Conclusion

The bcsD gene can improve the crystalline structure of the bacterial cellulose but there is not any significant difference between the amounts of cellulose produced by the recombinant and wild type E. coli Nissle 1917.

     

Heterologous biosynthesis of triterpenoid dammarenediol-II in engineered <Emphasis Type="Italic">Escherichia coli</Emphasis>

Objectives

To achieve heterologous biosynthesis of dammarenediol-II, which is the precursor of dammarane-type tetracyclic ginsenosides, by reconstituting the 2,3-oxidosqualene-derived triterpenoid biosynthetic pathway in Escherichia coli.

Results

By the strategy of synthetic biology, dammarenediol-II biosynthetic pathway was reconstituted in E. coli by co-expression of squalene synthase (SS), squalene epoxidase (SE), NADPH-cytochrome P450 reductase (CPR) from Saccharomyces cerevisiae, and SE from Methylococcus capsulatus (McSE), NADPH-cytochrome P450 reductase (CPR) from Arabidopsis thaliana. Sequences of transmembrane domains were truncated if necessary in each of the genes. Different sources of SE/CPR combinations were tested, during which two CPRs were detected to be new reductase partners of McSE. When the gene encoding dammarenediol-II synthase was co-expressed with the 2,3-oxidosqualene expression modules, dammarenediol-II was detected and the production was 8.63 mg l^?1 in E. coli under the shake-flask conditions.

Conclusions

Two E. coli chassis for production of dammarenediol-II were established which could be potentially applied in other triterpenoid production in E. coli when different oxidosqualene cyclases (OSCs) introduced into the system.

     

Biosynthesis of di-rhamnolipids and variations of congeners composition in genetically-engineered <Emphasis Type="Italic">Escherichia coli</Emphasis>

Objectives

To engineer Escherichia coli for the heterologous production of di-rhamnolipids, which are important biosurfactants but mainly produced by opportunistic pathogen Pseudomonas aeruginosa.

Results

The codon-optimized rhlAB and rhlC genes originating from P. aeruginosa and Burkholderia pseudomallei were combinatorially expressed in E. coli to produce di-rhamnolipids with varied congeners compositions. Genes involved in endogenous upstream pathways (rhamnose and fatty acids synthesis) were co-overexpressed with rhlAB–rhlC, resulting in variations of rhamnolipids production and congeners compositions. Under the shake-flask condition, co-overexpression of rfbD with rhlAB–rhlC increased rhamnolipids production (0.64 ± 0.02 g l^?1) than that in strain only expressing rhlAB–rhlC (0.446 ± 0.009 g l^?1), which was mainly composed of di-rhamnolipids congeners Rha–Rha–C₁₀–C₁₀.

Conclusion

Biosynthesis of di-rhamnolipids and variations of congeners composition in genetically engineered E. coli strains were achieved via combiniations of mono-/di-rhamnolipids synthesis modules and endogenous upstream modules.

     

<Emphasis Type="Italic">Rhizobium</Emphasis> strains in the biological control of the phytopathogenic fungi <Emphasis Type="Italic">Sclerotium</Emphasis> (<Emphasis Type="Italic">Athelia</Emphasis>) <Emphasis Type="Italic">rolfsii</Emphasis> on the common bean

Aims

To identify Rhizobium strains’ ability to biocontrol Sclerotium rolfsii, a fungus that causes serious damage to the common bean and other important crops, 78 previously isolated rhizobia from common bean were assessed.

Methods

Dual cultures, volatiles, indole-acetic acid (IAA), siderophore production and 16S rRNA sequencing were employed to select strains for pot and field experiments.

Results

Thirty-three antagonistic strains were detected in dual cultures, 16 of which were able to inhibit ≥84% fungus mycelial growth. Antagonistic strains produced up to 36.5 μg mL^?1 of IAA, and a direct correlation was verified between IAA production and mycelium inhibition. SEMIA 460 inhibited 45% of mycelial growth through volatile compounds. 16S rRNA sequences confirmed strains as Rhizobium species. In pot condition, common bean plants grown on S. rolfsii-infested soil and inoculated with SEMIA 4032, 4077, 4088, 4080, 4085, or 439 presented less or no disease symptoms. The most efficient strains under field conditions, SEMIA 439 and 4088, decreased disease incidence by 18.3 and 14.5% of the S. rolfsii-infested control.

Conclusions

Rhizobium strains could be strong antagonists towards S. rolfsii growth. SEMIA 4032, 4077, 4088, 4080, 4085, and 439 are effective in the biological control of the collar rot of the common bean.

     

Function of the <Emphasis Type="Italic">rel</Emphasis> Gene in <Emphasis Type="Italic">Escherichia coli</Emphasis>

Sokawa et al. suggest that rel^- strains of Escherichia coli possess abnormal protein synthesizing machinery, which cannot carry out normal protein synthesis when the supply of amino-acids is limited.     

Engineering of <Emphasis Type="Italic">Escherichia coli</Emphasis> for the synthesis of <Emphasis Type="Italic">N</Emphasis>-hydroxycinnamoyl tryptamine and serotonin

Plants synthesize various phenol amides. Among them, hydroxycinnamoyl (HC) tryptamines and serotonins exhibit antioxidant, anti-inflammatory, and anti-atherogenic activities. We synthesized HC–tryptamines and HC–serotonin from several HCs and either tryptamine or serotonin using Escherichia coli harboring the 4CL (4-coumaroyl CoA ligase) and CaHCTT [hydroxycinnamoyl-coenzyme A:serotonin N-(hydroxycinnamoyl)transferase] genes. E. coli was engineered to synthesize N-cinnamoyl tryptamine from glucose. TDC (tryptophan decarboxylase) and PAL (phenylalanine ammonia lyase) along with 4CL and CaHCTT were introduced into E. coli and the phenylalanine biosynthetic pathway of E. coli was engineered. Using this strategy, approximately 110.6 mg/L of N-cinnamoyl tryptamine was synthesized. By feeding 100 μM serotonin into the E. coli culture, which could induce the synthesis of cinnamic acid or p-coumaric acid, more than 99 μM of N-cinnamoyl serotonin and N-(p-coumaroyl) serotonin were synthesized.