Metabolic Engineering of Escherichia coli for Production of 2

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Biotechnology and Biological Transformations

Metabolic engineering of Escherichia coli for production of 2-phenylethanol and 2-phenylethylacetate from glucose Daoyi Guo, Lihua Zhang, Sijia Kong, Zhijie Liu, Xun Li, and Hong Pan J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.8b01594 • Publication Date (Web): 29 May 2018 Downloaded from http://pubs.acs.org on May 29, 2018

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Metabolic engineering of Escherichia coli for production of 2-phenylethanol and

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2-phenylethylacetate from glucose

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Daoyi Guo*§, Lihua Zhang§, Sijia Kong§, Zhijie Liu #, Xun Li§, Hong Pan*§

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Corresponding author: Tel: +86-797-8393536; E-mail address: [email protected]

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and [email protected]

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§

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Normal University, Ganzhou 341000, China

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#

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Laboratory of Industrial Microbiology, Hubei Collaborative Innovation Center for

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Key Laboratory of Organo-Pharmaceutical Chemistry, Jiangxi Province, Gannan

Key Laboratory of Fermentation Engineering (Ministry of Education), Hubei Key

Industrial Fermentation, Hubei University of Technology, Wuhan 430068, China

11 12 13 14 15 16 17 18 19 20 21 22

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ABSTRACT

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The rose-like odor 2-phenylethanol (2-PE) and its more fruit-like ester

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2-phenylethylacetate (2-PEAc) are two important aromatic compounds and have wide

27

applications. In the past, 2-PE and 2-PEAc were mainly produced from

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L-phenylalanine. In this study, the Escherichia coli was engineered to de novo

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biosynthesis of 2-PE and 2-PEAc from glucose. Firstly, overexpression of deregulated

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3-deoxy-D-arabinoheptulosonate-7-phosphate

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mutase/prephenate dehydratase pheAfbr for increasing phenylpyruvate production in E.

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coli. Subsequently, heterologous expression of decarboxylase kdc and overexpression

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of reductase yjgB for the conversion of phenylpyruvate to 2-PE. The engineered strain

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DG01 produced 578 mg/L of 2-PE. Finally, heterologous expression of an

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aminotransferase aro8 to redirect the metabolic flux to phenylpyruvate. 1016 mg/L of

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2-PE was accumulated in the engineered strain DG02. Alcohol acetyltransferase ATF1

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from S. cerevisiae can esterify a wide variety of alcohols including 2-PE. We have

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further demonstrated the biosynthesis of 2-PEAc from glucose by overexpressing atf1

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for the subsequent conversion of 2-PE to 2-PEAc. The engineered strain DG03

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produced 687 mg/L 2-PEAc.

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Keywords:

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2-phenylethylacetate.

metabolic

engineering;

synthase

Escherichia

43 44

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aroGfbr

coli;

and

chorismate

2-phenylethanol;

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INTRODUCTION

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The rose-like odor 2-phenylethanol (2-PE) and its more fruit-like ester

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2-phenylethylacetate (2-PEAc) are high-value flavor and fragrance compounds, and

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have a wide range of applications in the cosmetics, perfumery, and food industries.

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Although the production of 2-PE and 2-PEAc by chemical synthesis has advantages in

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cost, consumers prefer more natural or bio products in the area of flavor 1. However,

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such natural extracts of aroma compounds obtained from plant sources by physical

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processes are costly on account of low extraction yields 2, 3. In the past decades, great

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efforts have been made in the biosynthesis of 2-PE and 2-PEAc from L-phenylalanine

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4-6

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maximum titer of 2-PE and/or 2-PEAc. However, in order to achieve economic

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production of 2-PE and/or 2-PEAc, cheaper carbon substrate other than

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L-phenylalanine should be used. In recent years, construction of microbial cell

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factories that are able to produce value-added products directly from renewable

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carbon sources has made significant progress 7-10. Thus, the engineering of the diverse

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microbial pathways to biogenerate large quantities of aroma compounds presents an

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attractive alternative to extractions from plant sources.

. In those studies, L-phenylalanine is used as a starting substrate to reach the

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In this study, two de novo biosynthetic pathways for the production of 2-PE and

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2-PEAc were constructed in Escherichia coli (Figure 1). This study described here

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shows the way for the development of an economical process for biosynthesis of 2-PE

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and 2-PEAc directly from glucose.

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MATERIALS AND METHODS

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Enzymes, chemicals, and strains

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Benzyl alcohol and phenethyl propionate were purchased from Sigma-Aldrich

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(Steinheim, Germany). Restriction endonucleases and DNA polymerases were

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purchased from NEB (New England Biolabs). T4 DNA ligase, plasmid extraction kits,

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PCR purification kits and DNA extraction kits were purchased from Fermentas

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(Burlington, Canada). E. coli DH5α and E. coli BL21 (DE3) were purchased from

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TaKaRa (Dalian, China). The E. coli DH-5α was used for plasmid construction and

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screening. E. coli BL21 (DE3) was used as a host for fermentation to synthesize 2-PE

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and 2-PEAc. All other chemical reagents were analytically pure and purchased from

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Sinopharm Chemical Reagent Co., Ltd ( Shanghai, China).

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Plasmid construction

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All the primers used in this study are listed in Table 1. The strains and plasmids

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used in this study are listed in Table 2. AroGfbr (D146N, GenBank WP_001109196.1)

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was synthesized by Genewiz Biotech Co. Ltd and amplified by PCR using primers

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aroGfbr-XbaI and aroGfbr-SpeI-BamHI, and ligated into pET28a(+) via XbaI and

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BamHI to yield plasmid pDG11. PheAfbr (a truncated pheA, lacking the R-domain

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sequence for feedback inhibition by L-phenylalanine, GenBank NP_311489.1) was

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amplified by PCR from E. coli MG1655 genomic DNA using primers pheAfbr-XbaI

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and pheAfbr-SpeI-SalI, and ligated into pET28a(+) via XbaI and SalI to give pDG12.

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The XbaI-SalI fragments of pheAfbr from pDG12 was inserted into SpeI and SalI sites

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of pDG11 to give pDG13. The XbaI-SalI fragments of aroGfbr and pheAfbr from

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pDG13 was inserted into XbaI- and XhoI sites of pBBRMCS1 to give pDG14.

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Plasmid pPG34, which co-expression of decarboxylase kdc from Saccharomyces

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cerevisiae YPH499 and reductase yjgB from E. coli, was constructed in our previous

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study11. Aro8 gene from S. cerevisiae was amplified by PCR using the primer pair

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aro8-XbaI and aro8-NheI-BamHI, and ligated into pPG34 via NheI and XhoI to yield

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plasmid pDG15. Plasmid pPG37, which co-expression of kdc, yjgB, aro8 and atf1 was

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constructed in our previous study11.

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Shake flask cultures

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Overnight cultures (1 mL) of recombinant E. coli strains were transferred to 100

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mL modified M9 medium with 20 g/L glucose as previously described by Guo12 and

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shaken at 30°C. 36 mg/L chloromycetin and 50 mg/L kanamycin were added to the

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medium, when needed. When the OD600 reached about 0.6-0.8, IPTG was added to

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the medium for induction of gene expression at a final concentration of 0.1 mM.

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Samples were taken at regular intervals after induction and analyzed by GC/MS.

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Analytical methods

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Extraction and GC/MS analysis of 2-PE and 2-PEAc was carried out as previously

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described by Guo12. Glass beads were added to 10 mL culture broth for breaking the

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cells by vigorous shaking. 2-PE and 2-PEAc were extracted using ethyl acetate (15

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mL). After the centrifuge stratification, the upper ethyl acetate phase was withdrawn,

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evaporated to near dryness, and redissolved in 0.6 mL ethyl acetate. A 1 µL portion of

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the ethyl acetate phase was analysed after a split 10:1 injection on an Agilent 7890A

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GC equipped with an Agilent 5975 MS detector and an Agilent HP–5MS capillary

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column. The following temperature program was applied: 80°C for 1 min, an increase

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of 20°C/min to 250°C, and 250°C for 2 min. Benzyl alcohol and phenethyl propionate

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were used as internal standards for quantitative 2-PE and 2-PEAc, respectively.

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Results

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Developing a fermentation protocol for 2-PE production from glucose

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Phenylpyruvate is the precursor substrate for the biosynthesis of 2-PE. Recently,

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microbial 2-PE biosynthesis from L-phenylalanine was developed based on

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transamination of L-phenylalanine to phenylpyruvate by aminotransferase

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However, L-phenylalanine is an expensive precursor compared to glucose. To obtain

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2-PE from glucose, strains needs to have a strong capacity for phenylpyruvate

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synthesis. In this study, a biosynthetic pathway for 2-PE was established from glucose

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in E. coli. The overall pathway includes the upstream pathway from glucose to

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phenylpyruvate and the downstream pathway from phenylpyruvate to 2-PE.

13

.

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The phenylpyruvate can be de novo biosynthesized from glucose via

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L-phenylalanine pathway. However the efficiency is quite low because of feedback

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inhibition in L-phenylalanine pathway 14. Overexpression of feedback resistant mutant

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of

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bifunctional enzyme chorismate mutase/prephenate dehydratase (pheAfbr) is an

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essential strategy to overproduce phenylpyruvate. In this study, an artificial pathway

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was constructed for 2-PE biosynthesis in E. coli. This pathway comprised four gene

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products: feedback-resistant mutants of aroGfbr and pheAfbr for the efficient

3-deoxy-D-arabinoheptulosonate-7-phosphate

synthase

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(aroGfbr)

and

the

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overproduction of phenylpyruvate, 2-keto acid decarboxylase kdc for the conversion

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of phenylpyruvate to phenylacetaldehyde and aldehyde reductase yjgB for the

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conversion of phenylacetaldehyde to 2-PE. The resulting E. coli strain DG01 was

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cultured in a modified M9 medium in shake flasks and produced up to 578 ± 15.1

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mg/L 2-PE within 30 h (Table 3). 2-PE yield and productivity were calculated to be

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28.9 mg/g glycerol and 19.3 mg/L/h, respectively (Table 4). This proved that the

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synthetic pathway was functionally expressed in E. coli. Therefore, this strain could

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be used as a starting strain for further improvement of the production of 2-PE.

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Overexpression of aro8 gene to increase 2-PE production

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To further improve the production of 2-PE, inactivation of competing pathways

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or redirection of the byproducts to the desired intermediates is an effective strategy.

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Phenylpyruvate is precursor substrate for the biosynthesis of 2-PE. Therefore, we

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assumed that increasing phenylpyruvate availability would improve 2-PE production.

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Because phenylpyruvate can be converted to L-phenylalanine by aminotransferase

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tyrB catalysis, the knockout of tyrB gene may be able to promote 2-PE biosynthesis.

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However, a latest report showed that the knockout of tyrB gene caused the poor cell

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growth and eventually leaded to a dramatically decrease in 2-PE production. In this

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study, the heterologous overexpression of an aminotransferase aro8 that redirect

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phenylalanine to phenylpyruvate was used to improve the production of 2-PE. The

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resulting E. coli strain DG02 produced up to 1016 ± 52.9 mg/L 2-PE within 30 h

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(Table 3). 2-PE yield and productivity were calculated to be 50.8 mg/g glucose and

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33.9 mg/L/h, respectively (Table 4). This proves that overexpression of aro8 can

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effectively improve 2-PE production.

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Besides 2-PE, the significant formation of 2-PEAc, 4-hydroxyphenethyl alcohol,

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4-hydroxyphenethylacetate, 3-indolylethanol and 3-indolylacetate were also observed

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with this recombinant E. coli, as revealed by GC/MS analysis (Figure 2). We

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hypothesize that the precursor substrates for 4-hydroxyphenethyl alcohol and

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3-indolylethanol

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4-Hydroxyphenylpyruvic acid and tryptophan pathway intermediate indole-3-pyrucic

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acid, respectively. 4-Hydroxyphenylpyruvic acid and indole-3-pyrucic acid can be

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converted to 4-hydroxyphenylacetaldehyde and indole-3-acetaldehyde by 2-keto acid

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decarboxylase kdc. Then 4-hydroxyphenylacetaldehyde and indole-3-acetaldehyde

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were converted to 4-hydroxyphenethyl alcohol and 3-indolylethanol alcohol by

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aldehyde reductase yjgB. Finally, 4-hydroxyphenethyl alcohol and 3-indolylethanol

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alcohol were converted to 4-hydroxyphenethylacetate and 3-indolylacetate by an

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intrinsic alcohol acetyltransferase-like enzyme of E. coli15.

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Developing a fermentation protocol for 2-PEAc production from glucose

alcohol

are

from

tyrosine

pathway

intermediate

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Compared with 2-PE, 2-PEAc is a more fruit-like odor which is also widely used

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in fields of foods and cosmetics. In theory, 2-PEAc can be obtained from

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esterification of 2-PE in a 2-PE -producing microbe under catalysis of alcohol

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acyltransferase. Although our study shows that an alcohol acyltransferase-like enzyme

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exists in E. coli, the enzyme gene sequence has not been reported yet. Several studies

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showed that alcohol acetyltransferase ATF1 from S. cerevisiae can esterify a wide

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variety of alcohols including 2-PE

16, 17

. In this study, a fermentative route for

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biosynthesis of 2-PEAc was created by further heterologous expression of atf1 for the

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conversion of 2-PE to 2-PEAc in the 2-PE-producing strain. The resulting E. coli

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strain DG03 produced up to 687 ± 62.7 mg/L 2-PEAc within 30 h (Table 3). 2-PEAc

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yield and productivity were calculated to be 34.36 mg/g glucose and 22.9 mg/L/h,

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respectively (Table 4). This proves that ATF1 has a high catalytic activity.

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DISCUSSION

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The rose-like odor 2-PE and its more fruit-like ester 2-PEAc are two important

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perfumery compounds. Great efforts have been made on engineered E. coli or yeast

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for the biosynthesis of 2-PE and 2-PEAc from L-phenylalanine

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engineered S. cerevisiae for the production of 2-PE from L-phenylalanine and 4.8 g/L

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2-PE was produced in a medium containing 10 g/L L-phenylalanine after 195 h 4.

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Hwang et al. engineered E. coli for the whole-cell bioconversion of L-phenylalanine

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and 4.7 g/L 2-PE was produced in a medium containing 100 mM L-phenylalanine 22.

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A cofactor self-sufficient system was developed for enhanced production of 2-PE in E.

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coli 23. 2.2 g/L 2-PE and 1.3 g/L 2-PEAc was produced from 9 g/L L-phenylalanine in

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Kluyveromyces marxianus CBS 600 by the use of in situ product removal (ISPR)

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technique

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used to reduce the cost of production of 2-PE and 2-PEAc. A pathway was

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constructed for the biosynthesis of 2-PE from glucose in E. coli. This pathway

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comprised four gene products: a tyrosine-sensitive DAHP synthase aroF and pheAfbr

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from E. coli, phenylpyruvate decarboxylase kdc from Pichia pastoris GS115 and

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alcohol dehydrogenase adh1 from S. cerevisiae S288c25. However, the titer and yield

18-21

. Kim et al.

24

. However, compared with L-phenylalanine, cheaper substrate should be

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of 2-PE (0.285 g/L and 14.3 mg/g) produced from 20 g/L glucose by this engineered

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E. coli is low. Thus, screening of more active candidate enzymes (such as high

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activity phenylpyruvate decarboxylase) and replacement of wild-type aroF to a

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feedback resistant mutant of DAHP synthase in the future is a promising strategy for

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enhancing 2-PE production. A engineered Kluyveromyces marxianus strain produced

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up to 1.3 g/L of 2-PE from 20 g/L glucose after 72 h cultivation by overexpressing a

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feedback resistant DAHP synthase aroGfbr from Klebsiella pneumonia 26. Because this

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strain requires a long fermentation process for production of 2-PE, the productivity

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(18.1 mg/L/h) is relatively low.

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Compared with yeast, E. coli has a faster growth rate. Here, we attempted to

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engineer E. coli for biosynthesis of 2-PE from glucose. The overall pathway includes

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the upstream pathway from glucose to phenylpyruvate and the downstream pathway

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from phenylpyruvate to 2-PE. The precursor substrate phenylpyruvate can be de novo

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synthesized from glucose via L-phenylalanine pathway. Among the L-phenylalanine

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pathway, the enzyme DAHP synthase and the bifunctional enzyme chorismate

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mutase/prephenate dehydratase PheA are the two key rate-limiting steps toward the

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synthesis of phenylpyruvate27-29. E. coli has three DAHP synthase isoenzymes which

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are encoded by aroF, aroG and aroH. Because AroG contributes most of the overall

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DAHPS activity (about 80%), it is often used as the major candidate enzyme for

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biosynthesis of aromatic amino acids

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variants aroGfbr and pheAfbr have been identified, most of them are thermally unstable

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30, 32-34

30, 31

. Although many feedback resistant (fbr)

. The fermentation performances of six aroGfbr mutants were compared and it is

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found that aroGfbr (D146N) with a good thermostability is the best mutant for

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L-phenylalanine accumulation35. A truncated PheA (lacking the R-domain sequence

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for feedback inhibition by L-phenylalanine) could retain the native catalytic activities

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and thermostability, but release the L-phenylalanine feedback inhibition

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study, the aroGfbr (D146N) and the truncated pheA mentioned above were chosen and

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overexpressed to increase the formation of phenylpyruvate from glucose. Our group

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has reported that the 2-keto acid decarboxylase KDC from S. cerevisiae and aldehyde

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reductase YjgB from E. coli can efficiently convert phenylpyruvate to 2-PE (>82%)11.

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So, the two enzymes mentioned above were chosen to make up the downstream

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pathway from phenylpyruvate to 2-PE. The resulting E. coli strain DG01 produced up

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to 578 ± 15.1 mg/L 2-PE.

35, 36

. In this

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The phenylpyruvate availability is limited due to the endogenous conversion of

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phenylpyruvate to L-phenylalanine by aminotransferase TyrB in E. coli. A previous

234

study showed that knockout of the tyrB gene will cause cell growth to be inhibited

235

and eventually leads to a dramatically decrease in 2-PE production

236

we

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aminotransferase aro8. The resulting E. coli strain DG02 produced up to 1016 ± 52.9

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mg/L 2-PE which is the highest titer reported for the de novo biosynthesis of 2-PE by

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metabolically engineered E. coli so far. Recently, Koma et al reported the biosynthesis

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of 2-PE from glucose through co-expression of aroGfbr, pheAfbr, ipdC and aldehyde

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reductase gen (adhC, yqhD, yjgB or yahK) 37. The titer of 2-PE is about 5.7-6.5 mM

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(695-793 mg/L). Finally, we have further demonstrated the biosynthesis of 2-PEAc

redirect

L-phenylalanine

to

phenylpyruvate

by

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25

. In this study,

overexpression

of

an

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from glucose by overexpressing atf1 for the subsequent conversion 2-PE to 2-PEAc.

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To our knowledge, this is the first report on the biosynthesis of 2-PEAc directly from

245

a renewable carbon source. The resulting E. coli strain DG03 produced up to 687 ±

246

62.7 mg/L 2-PEAc. Our group has reported that the biosynthesis of 2-PEAc from

247

L-phenylalanine by engineered E. coli. We found that a large amount of 2-PE failed to

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be effectively converted to 2-PEAc. We hypothesize that the reason for the low

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conversion is the imbalance of the two precursor substrates, 2-PE and acetyl-CoA.

250

2-PE is rapidly synthesized and secreted to the outside of the cell in a synthetic

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system using L-phenylalanine as a precursor substrate and thus could not be esterified

252

in time to 2-PEAc.

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The aim of this research was to create a functional synthetic pathway in E. coli

254

and develop the completely fermentative route for producing 2-PE and 2-PEAc from

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glucose. It has been demonstrated that 2-PE and 2-PEAc has inhibitory effects on cell

256

growth of E. coli when their concentrations are higher than 1.0 g/L

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improvement of the yield of 2-PE and 2-PEAc by synthetic biology technology may

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be hindered by product toxicity. Several studies showed that in situ product removal

259

(ISPR) technique (such as two-phase culture system) can effectively overcome the

260

limitation by product toxicity, which resulted in significant improvement of their yield

261

38-40

262

optimization (For example, removal of the product, optimization of culture medium,

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fermentation temperature and pH) will be needed to improve the production of 2-PE

264

and 2-PEAc.

25

. Further

. Thus, future efforts to further strain improvement and fermentative process

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Funding information

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This work was supported by National Natural Science Foundation of China

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(81460312).

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Compliance with ethical standards

269

Conflict of interest The authors declare that they have no competing interests.

270

Ethics approval

271

or animals performed by any of the authors.

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13. Etschmann, M. M. W.; Sell, D.; Schrader, J., Screening of yeasts for the production of the aroma compound 2-phenylethanol in a molasses-based medium. Biotechnology Letters 2003, 25, 531-536. 14. Gallardo, E.; De, D. S.; Zamora, R.; Derdelinckx, G.; Delvaux, F. R.; Hidalgo, F. J., Influence of lipids in the generation of phenylacetaldehyde in wort-related model systems. Journal of Agricultural & Food Chemistry 2008, 56, 3155-9. 15. Liu, W.; Xu, X.; Zhang, R.; Cheng, T.; Cao, Y.; Li, X.; Guo, J.; Liu, H.; Xian, M., EngineeringEscherichia colifor high-yield geraniol production with biotransformation of geranyl acetate to geraniol under fed-batch culture. Biotechnology for Biofuels 2016, 9, 58. 16. Guo, D. Y.; Pan, H.; Li, X., Metabolic engineering of Escherichia coli for production of biodiesel from fatty alcohols and acetyl-CoA. Applied Microbiology & Biotechnology 2015, 99, 7805-7812. 17. Rodriguez, G. M.; Tashiro, Y.; Atsumi, S., Expanding ester biosynthesis in Escherichia coli. Nature Chemical Biology 2014, 10, 259. 18. Hazelwood, L. A.; Daran, J. M.; van Maris, A. J.; Pronk, J. T.; Dickinson, J. R., The Ehrlich pathway for fusel alcohol production: a century of research on Saccharomyces cerevisiae metabolism. Applied & Environmental Microbiology 2008, 74, 2259-2266. 19. Eshkol, N.; Sendovski, M.; Bahalul, M.; Katzezov, T.; Kashi, Y.; Fishman, A., Production of 2-phenylethanol from L-phenylalanine by a stress tolerant Saccharomyces cerevisiae strain. Journal of Applied Microbiology 2009, 106, 534-42. 20. Morrissey, J. P.; Etschmann, M. M. W.; Schrader, J.; Billerbeck, G. M., Cell factory applications of the yeast Kluyveromyces marxianus for the biotechnological production of natural flavour and fragrance molecules. Yeast 2015, 32, 3-16. 21. Stark, D.; Münch, T.; Sonnleitner, B.; Marison, I. W.; Stockar, U. V., Extractive Bioconversion of 2-Phenylethanol from l -Phenylalanine by Saccharomyces cerevisiae. Biotechnol Prog 2002, 18, 514-523. 22. Hwang, J. Y.; Park, J.; Seo, J. H.; Cha, M.; Cho, B. K.; Kim, J.; Kim, B. G., Simultaneous synthesis of 2-phenylethanol and L-homophenylalanine using aromatic transaminase with yeast Ehrlich pathway. Biotechnology & Bioengineering 2009, 102, 1323-9. 23. Wang, P.; Yang, X.; Lin, B.; Huang, J.; Tao, Y., Cofactor self-sufficient whole-cell biocatalysts for the production of 2-phenylethanol. Metabolic Engineering 2017, 44, 143. 24. Etschmann, M. M.; Sell, D.; Schrader, J., Production of 2-phenylethanol and 2-phenylethylacetate from L-phenylalanine by coupling whole-cell biocatalysis with organophilic pervaporation. Biotechnology & Bioengineering 2005, 92, 624-34. 25. Kang, Z.; Zhang, C.; Du, G.; Chen, J., Metabolic Engineering of Escherichia coli for Production of 2-phenylethanol from Renewable Glucose. Applied Biochemistry & Biotechnology 2014, 172, 2012-21. 26. Kim, T. Y.; Lee, S. W.; Oh, M. K., Biosynthesis of 2-phenylethanol from glucose with genetically engineered Kluyveromyces marxianus. Enzyme & Microbial Technology 2014, 61-62, 44. 27. Báezviveros, J. L.; Osuna, J.; Hernándezchávez, G.; Soberón, X.; Bolívar, F.; Gosset, G., Metabolic engineering and protein directed evolution increase the yield of L-phenylalanine synthesized from glucose in Escherichia coli. Biotechnology & Bioengineering 2004, 87, 516-524. 28. Doroshenko, V. G.; Tsyrenzhapova, I. S.; Krylov, A. A.; Kiseleva, E. M.; Ermishev, V. Y.; Kazakova, S. M.; Biryukova, I. V.; Mashko, S. V., Pho regulon promoter-mediated transcription of the key pathway gene aroGFbr improves the performance of an L-phenylalanine-producing Escherichia coli strain. Applied Microbiology & Biotechnology 2010, 88, 1287. 29. Kikuchi, Y.; Tsujimoto, K.; Kurahashi, O., Mutational analysis of the feedback sites of

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phenylalanine-sensitive 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase of Escherichia coli. Appl Environ Microbiol 1997, 63, 761-762. 30. Sprenger, G. A., From scratch to value: engineering Escherichia coli wild type cells to the production of l -phenylalanine and other fine chemicals derived from chorismate. Applied Microbiology & Biotechnology 2007, 75, 739-49. 31. Rodriguez, A.; Martínez, J. A.; Flores, N.; Escalante, A.; Gosset, G.; Bolivar, F., Engineering Escherichia coli to overproduce aromatic amino acids and derived compounds. Microbial Cell Factories 2014, 13, 126. 32. Chandran, S. S.; Yi, J.; Draths, K. M.; Von, D. R.; Weber, W.; Frost, J. W., Phosphoenolpyruvate availability and the biosynthesis of shikimic acid. Biotechnology Progress 2003, 19, 808. 33. Flores, N.; Xiao, J.; Berry, A.; Bolivar, F.; Valle, F., Pathway engineering for the production of aromatic compounds in Escherichia coli. Nature Biotechnology 1996, 14, 620. 34. Gerigk, M.; Bujnicki, R.; Ganpo‐Nkwenkwa, E.; Bongaerts, J.; Sprenger, G.; Takors, R., Process control for enhanced L-phenylalanine production using different recombinant Escherichia coli strains. Biotechnology & Bioengineering 2002, 80, 746. 35. Liu, S. P.; Xiao, M. R.; Zhang, L.; Xu, J.; Ding, Z. Y.; Gu, Z. H.; Shi, G. Y., Production of l -phenylalanine from glucose by metabolic engineering of wild type Escherichia coli W3110. Process Biochemistry 2013, 48, 413-419. 36. Zhang, S.; Pohnert, G.; Kongsaeree, P.; Wilson, D. B.; Clardy, J.; Ganem, B., Chorismate mutase-prephenate dehydratase from Escherichia coli. Study of catalytic and regulatory domains using genetically engineered proteins. Febs Journal 1998, 273, 6248. 37. Koma, D.; Yamanaka, H.; Moriyoshi, K.; Ohmoto, T.; Sakai, K., Production of aromatic compounds by metabolically engineered Escherichia coli with an expanded shikimate pathway. Applied & Environmental Microbiology 2012, 78, 6203-16. 38. Etschmann, M. M. W.; Schrader, J., An aqueous–organic two-phase bioprocess for efficient production of the natural aroma chemicals 2-phenylethanol and 2-phenylethylacetate with yeast. Applied Microbiology & Biotechnology 2006, 71, 440. 39. Gao, F.; Daugulis, A. J., Bioproduction of the aroma compound 2-phenylethanol in a solid-liquid two-phase partitioning bioreactor system by Kluyveromyces marxianus. Biotechnology & Bioengineering 2009, 104, 332-9. 40. Mei, J.; Min, H.; Lü, Z., Enhanced biotransformation of l -phenylalanine to 2-phenylethanol using an in situ product adsorption technique. Process Biochemistry 2009, 44, 886-890.

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Table 1. Primers used in this study

386

Primer name aroGfbr-XbaI

Sequence (5’-3’) GTATCTAGAAAGAGGAGATATAATGAATTATCAGAA CGACGATTTACGC

aroGfbr-SpeI-BamHI

TATGGATCCACTAGTTTACCCGCGACGCGCTTTTA

pheAfbr-XbaI

GTATCTAGAAAGAGGAGATATAATGACATCGGAAAA CCCGTTACTG

pheAfbr-SpeI-SalI

ATATGTCGACACTAGTTCACAACGTGGTTTTCGCCGG A

aro8-XbaI

AACTCTAGATTTAAGAAGGAGATATAATGATGACTT TACCTGAATCAAAAGACTTTTC

aro8-NheI-BamHI

ACAGGATCCGCTAGCCTATTTGGAAATACCAAATTCT TCGTATAA

387 388 389 390 391 392 393

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Table 2. Plasmids and strains used in this study

398

Plasmids/strains

Properties

Source/reference

pDG11

pET28a; pT7: aroGfbr

This study

pDG12

pET28a; pT7: pheAfbr

This study

pDG13

pET28a; pT7: aroGfbr and pheAfbr

This study

pDG14

pBBRMCS1; pT7: aroGfbr and pheAfbr

This study

pPG34

pET28a; pT7: kdc and yjgB

11

pDG15

pET28a; pT7: kdc, yjgB and aro8

This study

pPG37

pET28a; pT7: kdc, yjgB, aro8 and atf1

11

DG01

BL21/ pDG14/ pPG34

This study

DG02

BL21/ pDG14/ pDG15

This study

DG03

BL21/ pDG14/ pPG37

This study

Plasmids

Strains

399 400 401 402

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Table 3. 2-PE and 2-PEAc production in engineered E. coli strains. Data are the

407

mean values of three independent experiments ± SD. Strains

2-PE (mg/L)

2-PEAc (mg/L)

DG01

578 ± 15.1

188 ± 12.2

DG02

1016 ± 52.9

246 ± 47.8

DG03

46 ± 10.7

687 ± 62.7

408 409 410 411 412 413 414 415 416 417 418 419 420 421

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Table 4. The yield and productivity calculations in engineered E. coli strains in shake

427

flasks for 30 h. Yield calculated by milligrams 2-PE or 2-PEAc produced divided by

428

grams glucose consumed. Productivity calculated by concentration of 2-PE or 2-PEAc

429

produced per hour. Data are the mean values of three independent experiments ± SD. Strains

Yield (mg/g)

Productivity (mg/L/h)

DG01

28.9 ± 0.75

19.3 ± 0.50

DG02

50.8 ± 2.64

33.9 ± 1.76

DG03

34.36 ± 3.14

22.9 ± 2.09

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Figure legends:

444

Figure.1. Engineered pathways for production of 2-PE and 2-PEAc from glucose.

445

Figure.2. GC/MS analyses of 2-PE and 2-PEAc from engineered E. coli strains.

446

Identified substances: 1, benzyl alcohol (internal standard); 2, 2-PE; 3, 2-PEAc; 4,

447

phenethyl propionate (internal standard); 5, 4-hydroxyphenethyl alcohol; 6,

448

4-hydroxyphenethylacetate; 7, 3-indolylethanol; 8, 3-indolylacetate.

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466 467

Figure.1. Engineered pathways for production of 2-PE and 2-PEAc from glucose.

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478 479

Figure.2. GC/MS analyses of 2-PE and 2-PEAc from engineered E. coli strains.

480

Identified substances: 1, benzyl alcohol (internal standard); 2, 2-PE; 3, 2-PEAc; 4,

481

phenethyl propionate (internal standard); 5, 4-hydroxyphenethyl alcohol; 6,

482

4-hydroxyphenethylacetate; 7, 3-indolylethanol; 8, 3-indolylacetate.

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TOC graphic 224x186mm (300 x 300 DPI)

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