NOVEL BACTERIAL STRAINS FOR THE PRODUCTION OF VANILLIN

The present patent application is filed pursuant to 35 U.S.C. § 371 as a U.S. National Phase Application of International Patent Application No. PCT/FR2016/052403 filed Sep. 22, 2016, claiming the benefit of priority to French Patent Application No. 1559142 filed Sep. 29, 2015. The International Application was published as WO 2017/055712 on Apr. 6, 2017. The contents of each of the aforementioned patent applications are herein incorporated by reference in their entirety.

The instant application contains a Sequence Listing which has been submitted electronically in ASCII format and is hereby incorporated by reference in its entirety. Said ASCII copy, created on Mar. 16, 2018, is named 44980002023_SL.txt and is 16,194 bytes in size.

The present invention relates to the field of production of vanillin. It relates particularly to an Amycolatopsis strain derived from the Amycolatopsis Zyl 926 strain, the preparation process thereof, and the integration cassette thereof.

Vanillin is one of the major components constituting vanilla extract, which is a powerful natural aroma obtained from the bean of an orchid. The extraction of this molecule from vanilla beans is very expensive; the quantities produced are limited and do not cover market demand. Other ways of obtaining vanillin have been sought.

It is for example possible to obtain vanillin from ferulic acid by bioconversion reaction with bacteria. In this patent application, we are interested only in the ferulic acid bioconversion pathway of vanillin by bacteria.

Vanillin production by bacteria is done by deacetylation of ferulic acid by means of the following 3 steps:

1. Activation of ferulic acid in feruloyl-CoA, activation being catalysed by an enzyme, the feruloyl-CoA ligase, hereinafter FCS;

2. Hydroxylation of the feruloyl-CoA in 4-Hydroxy-3-methoxyphenyl-P-hydroxypropionyl-CoA, hydroxylation being catalysed by an enzyme, Enoyl-CoA Hydratase/Aldolase, hereinafter ECH;

3. Deacetylation of the 4-Hydroxy-3-methoxyphenyl-β-hydroxypropionyl-CoA allowing vanillin to be obtained, also catalyzed by the enzyme ECH.

The vanillin obtained can subsequently be oxidized to vanillic acid by an enzyme, vanillin dehydrogenase, hereinafter VDH. However, converting vanillin to vanillic acid is not desired because only the vanillin has the desired aromatic characteristics.

According to the EC nomenclature of the enzymes (Enzyme Commission number):

• • the enzyme FCS has the code EC 6.2.1.34,
  • the enzyme ECH has the codes EC 4.2.1.101 and EC 4.1.2.41,
  • the enzyme VDH has the code EC 1.2.1.67.

EP 2 721 148 A1 describes a microorganism of the genus Amycolatopsis not comprising the gene encoding the VDH, said microorganism making it possible to produce vanillin from ferulic acid.

EP 1 611 244 A1 describes a vanillin production process that does not use organic solvents during purification, as they are now considered undesirable in the food industry, to obtain a vanillin called “natural.” During said vanillin production process, the biotransformation of ferulic acid into vanillin is performed by the Amycolatopsis strain IMI390106, also called the Zyl 926 strain or the Amycolatopsis Zyl 926 strain.

The book “Practical Streptomyces Genetics”, 2000, Kieser, et al. published by The John Innes Foundation, ISBN 0-7084-0623-8, in Chapter 10, describes a method of transfer between Escherichia coli and Streptomyces for DNA integration at specific sites.

However, the strains of the prior art used in the bioconversion reaction do not allow an optimal conversion of ferulic acid to vanillin. Given the cost of ferulic acid, there remains a need for new strains of bacteria ensuring better conversion of ferulic acid to vanillin.

The applicant has thus developed new strains of bacteria through an original transformation method, allowing for an improved molar yield during the bioconversion reaction.

The invention thus provides an Amycolatopsis strain derived from the Amycolatopsis Zyl 926 strain, having at least one additional copy of FCS and ECH genes integrated at the integration site of the phage φC31.

The invention also relates to a method for obtaining an Amycolatopsis strain derived from the Amycolatopsis Zyl 926 strain by interspecific transfer.

The invention also relates to an integration cassette comprising the expression cassette of ECH genes and FCS.

The invention also relates to the use of said strains in a process for obtaining vanillin.

The invention also relates to a vanillin production process.

The present invention relates to novel bacterial strains of the Amycolatopsis genus particularly useful for the bioconversion reaction of ferulic acid to vanillin.

After extensive research, the inventors have developed new Amycolatopsis strains derived from Amycolatopsis Zyl 926 strain to have an improved molar yield compared to the prior art, for the bioconversion reaction of ferulic acid to vanillin through overexpression of FCS and ECH genes into the genome of the 926 Amycolatopsis Zyl strain.

A bioconversion molar yield is defined as the ratio between the number of moles of the product obtained, in our case vanillin, divided by the number of moles of substrate implemented, in this case, ferulic acid. When in percentage, this ratio is multiplied by 100.

“Improved molar yield compared to the prior art” means a molar yield of bioconversion greater than or equal to 80%, preferably greater than or equal to 85%, and more preferably equal to greater than 90%.

The Amycolatopsis Zyl 926 strain was filed with the CABI Bioscience, UK science centre in Egham, under the number IMI 390106 on 2 Mar. 2003.

The terms “Zyl 926 strain”, “926 Amycolatopsis Zyl strain,” “Amycolatopsis IMI 390106 strain,” “Amycolatopsis strain filed with the CABI Bioscience under number IMI 390106” are here synonymous.

“Amycolatopsis strain(s) derived from the strain Amycolatopsis Zyl 926” means all strains obtained after transformation of the Zyl 926 strain by interspecific transfer for integrating at least one additional copy of FCS and ECH genes.

The inventors have further demonstrated that new strains of the invention can also improve productivity and consumption of almost all of the ferulic acid in the bioconversion reaction.

“Consuming substantially all of the ferulic acid” means that at least 98% of ferulic acid is consumed during the bioconversion reaction, preferably at least 99%, and even more preferably 100%.

The present invention therefore relates to an Amycolatopsis strain derived from the Amycolatopsis Zyl 926 strain comprising:

• • at least one additional copy of the FCS gene encoding Feruloyl-CoA Synthetase having the protein sequence SEQ ID NO: 1 or any sequence at least 80%, preferably at least 90%, and more preferably at least 95% identical to SEQ ID NO: 1, and
  • at least one additional copy of the ECH gene encoding Enoyl-CoA Hydratase/Aldolase having the protein sequence SEQ ID NO: 2 or any sequence at least 80%, preferably at least 90%, and more preferably at least 95% identical to SEQ ID NO: 2,

said additional copies of genes FCS and ECH being specifically integrated at the integration site of the phage φC31, also called attB site.

The article by Keravala et al. (Methods Mol Biol. 2008) mentions the use of the phage φC31 integrase as a mediator for chromosomal integration site-specific. It thus allows a unidirectional recombination between two att sites called attP and attB.

“Extra copy of the gene” means any copy of an integrated gene of interest into the genome of a strain as well as copies of the gene of interest initially present in the genome.

A protein sequence or nucleic called identical to another when the alignment between the two sequences is perfect, i.e. when there is a perfect correspondence respectively between amino acids or nucleic acids of each sequence.

The sequence identity percentage is calculated by giving a score of 0 or 1 for each amino acid or base sequence as to whether there is identity or not.

The terms “ECH gene encoding Enoyl-CoA Hydratase/Aldolase” and “FCS gene encoding Feruloyl-CoA Synthetase” should not be narrowly interpreted but should also encompass sequences encoding functional variants of these enzymes.

Typically, functional variants of these enzymes FCS and ECH have a protein sequence having an identity percentage of at least 80%, preferably at least 90% and more particularly preferably at least 95% with the protein sequences SEQ ID NO: 1 and SEQ ID NO: 2.

Advantageously, the present invention relates to an Amycolatopsis strain wherein additional copies of FCS and ECH genes are placed under the control of the strong ermE* promoter associated with a ribosome binding site, called RBS.

The ermE* promoter is the ermE promoter modified to give a strong and constitutive expression.

The ermE* promoter has nucleic acid sequence SEQ ID NO: 6 or any sequence at least 90%, preferably at least 95% and even more preferably at least 99% identical to SEQ ID NO: 6.

The sequence of the ermE* promoter is described in the article by Bibb et al. (Mol Microbiol. 1994 November; 14(3):533-45)

To obtain the new original strains of the invention that overexpress the FCS and ECH genes, the inventors revealed after much research and experimentation that the interspecific transfer method enabled transformants to be obtained that have integrated at least one supplementary copy of the genes ECH and FCS and that the success of this gene integration method was locus dependent.

The term “locus dependent” means that supplementary copies of genes of interest must be specifically integrated at the φC31 phage integration site.

The present invention therefore relates to a process for obtaining an Amycolatopsis strain derived from the Amycolatopsis Zyl 926 strain as described above, comprising the steps of:

a) amplification by PCR of the FCS genes encoding Feruloyl-CoA Synthetase having the sequence SEQ ID NO: 1 or any sequence at least 80%, preferably at least 90%, and more preferably at least 95% identical to SEQ ID NO: 1 and ECH encoding Enoyl-CoA Hydratase/Aldolase having the sequence SEQ ID NO: 2 or any sequence at least 80%, preferably at least 90%, and even more preferably at least 95% identical to SEQ ID NO: 2, isolated from an Amycolatopsis strain;

b) constructing a vector carrying the nucleic acid sequences obtained in step a, from pSET152 plasmid having:

• • i. the int gene encoding phage φC31 integrase having the sequence of nucleotide sequence SEQ ID NO: 3 or any sequence at least 80%, preferably at least 90%, and more preferably at least 95% identical to the sequence SEQ ID NO: 3,
  • ii. phage binding site φC31 hereinafter attP site with the nucleotide sequence SEQ ID NO: 4, and
  • iii. the functional origin of transfer oriT with the nucleotide sequence SEQ ID NO: 5 or any sequence at least 90%, preferably at least 95% and even more preferably at least 99% identical to the sequence SEQ ID NO: 5;

c) transformation by electroporation of the ET12567 Escherichia coli strain with a transferring plasmid comprising all of the genes encoding the transfer machinery the origin of transfer oriT of which was rendered non-functional, and the vector was constructed in step b;

d) selection of the ET12567 Escherichia coli strains transformed in step c by culture in a medium containing neomycin and beta-lactam;

e) interspecific transfer between ET12567 Escherichia coli strains transformed and selected in steps c and d and the strain Amycolatopsis Zyl 926, by setting coculture;

f) selection of the Amycolatopsis Zyl 926 strains having integrated at least one additional copy of the FCS gene encoding feruloyl-CoA synthetase having the sequence SEQ ID NO: 1 or any sequence at least 80%, preferably at least 90%, and more preferably at least 95% identical to SEQ ID NO: 1 and at least one additional copy of the ECH gene encoding enoyl-CoA hydratase having the sequence SEQ ID NO: 2 or any sequence at least 80%, preferably at least 90%, and more preferably at least 95% identical to SEQ ID NO: 2 according to step e, by culturing on a medium containing apramycin.

The FCS and ECH genes have been isolated and amplified from an Amycolatopsis strain by a PCR technique known to those skilled in the art. Due to special features of the Amycolatopsis genome, the Phusion® High-Fidelity PCR Master Mix with GC Buffer kit from New England Biolabs was preferably used with the GC Buffer.

The sequences of the primers used are the following sequences:

Preferably the FCS and ECH genes were isolated from the strain Amycolatopsis Zyl 926.

The pSET152 plasmid has apramycin resistance.

The vector construction according to step b) is made by cloning additional copies of genes FCS and ECH amplified in step a in pSET152 plasmid (Bierman et al, Gene, 116 (1): 43-49, 1992). The PCR product containing ECH and FCS genes was obtained using as genomic DNA matrix of the strain Zyl926 and Van-ECH-F primer (SEQ ID NO: 7) and Van-ECH-R (SEQ ID NO: 8). The fragment to be integrated was obtained by HindIII digestion (+ Klenow) and XbaI. The HindIII fragments (Klenow+) and XbaI were cloned in the EcoRV and XbaI pSET152 sites.

Int gene means the gene encoding the integrase of phage φC31 with the protein sequence SEQ ID NO: 3 or any sequence at least 80%, preferably at least 90%, and more preferably at least 95% identical to the sequence SEQ ID NO: 3.

The phage attachment site φC31, also called attP site present in the pSET152 plasmid, has the sequence SEQ ID NO: 4.

SEQ ID NO: 4 is the following:

Selecting ET 12567 Escherichia coli strains transformed in step c) is performed on the basis of the acquisition by these transformed strains of neomycin resistance and beta-lactam.

Co-culturing for the production of the interspecific transfer of step e), is carried out under conventional conditions known to the person skilled in the art (Bierman et al, 1992 see above) and preferably by bringing into contact for several hours a part of the ET12567 Escherichia coli obtained in step d. previously transformed and made ready for transformation, and secondly, Amycolatopsis Zyl 926 cells previously synchronized for germination by heating.

The Escherichia coli ET12567 strain is ATCC BAA-525 (MacNeil et al, Gene 111. 61-68, 1992).

The selection according to step f) of Amycolatopsis Zyl 926 strains having integrated at least one copy of FCS and ECH genes is performed on the basis of the acquisition by these strains of apramycin resistance.

According to a particular embodiment, the invention more particularly relates to a method of obtaining an Amycolatopsis strain derived from the Amycolatopsis Zyl 926 strain as described above, comprising an additional step b′, between steps b and c, amplification and cloning of the strong ermE* promoter in the vector constructed in step b, said ermE* promoter being associated with a ribosome binding site, called RBS.

The ermE* promoter has the sequence SEQ ID NO: 6 or any sequence at least 90%, preferably at least 95% and even more preferably at least 99% identical to SEQ ID NO: 6.

According to a particular embodiment, the invention particularly relates to a method for obtaining an Amycolatopsis strain derived from the Amycolatopsis Zyl 926 strain as described above, wherein the conjugating plasmid of step c is the pUZ8002 plasmid described in the book “Practical Streptomyces Genetics”, 2000, Kieser, et al, chapter 10, published by The John Innes Foundation, ISBN 0-7084-0623-8,

According to a particular embodiment, the invention more particularly relates to a method of obtaining an Amycolatopsis strain derived from the Amycolatopsis Zyl 926 strain as described above, wherein the beta-lactam from step d is ampicillin.

The present invention also purposes an Amycolatopsis strain derived from the Amycolatopsis Zyl 926 strain obtainable by the process as defined above.

The present invention also particularly relates to an Amycolatopsis strain derived from the strain Amycolatopsis Zyl 926, obtainable by the process as defined above, which is selected from the strain filed with the CNCM under the number I-4922, the strain filed with the CNCM under the number I-4923 and the strain filed with the CNCM under the number I-4924.

The strains I-4922, I-4923 and I-4924 are strains ofAmycolatopsis sp. filed under the Budapest Treaty, on 11 Dec. 2014 with the CNCM (Collection Nationale de Cultures de Microorganismes [National Collection of Microorganism Cultures]), 25 rue du Docteur Roux, 75724 Paris Cedex 15, France.

The present invention also relates to an integration cassette comprising:

i. an expression cassette of the FCS gene encoding feruloyl-CoA synthetase having the sequence SEQ ID NO: 1 or any sequence at least 80%, preferably at least 90%, and more preferably at least 95% identical to SEQ ID NO: 1 and ECH encoding Enoyl-CoA Hydratase/Aldolase having the sequence SEQ ID NO: 2 or any sequence at least 80%, preferably at least 90%, and even more preferably at least 95% identical to SEQ ID NO: 2;

ii. means for integration of the cassette into the genome of the strain Amycolatopsis Zyl 926, including the int gene of the phage φC31 having the sequence SEQ ID NO: 3 or any sequence at least 80%, preferably at least 90%, and more preferably at least 95% identical to the sequence SEQ ID NO: 3 and the φC31 phage attachment site called attP site having the sequence SEQ ID NO: 4;

iii. means for selecting Escherichia coli ET12567 strains transformed comprising neomycin and a beta-lactam;

iv. means for selecting Amycolatopsis Zyl926 strains having integrated said integration cassette comprising a marker for resistance to apramycin.

An integration cassette is a genetic construct comprising the necessary tools for the integration of one or more genes of interest into the genome of an organism, here the strain Amycolatopsis 926 Zyl.

According to a particular embodiment of the invention, the genes encoding Feruloyl-CoA Synthetase and Enoyl-CoA Hydratase/Aldolase of the expression cassette described above are placed under the control of strong ermE* promoter having the sequence SEQ ID NO: 6 or any sequence at least 90%, preferably at least 95% and even more preferably at least 99% identical to SEQ ID NO: 6 said ermE* promoter being associated with a ribosome binding site, also known as RBS.

According to a particular embodiment, the invention more particularly relates to an integration cassette as described above, wherein the beta-lactam is ampicillin.

The invention also relates to the use of new Amycolatopsis sp strains derived from the Amycolatopsis Zyl 926 strain as described above, in a vanillin production process.

The present invention also relates to a method of producing vanillin comprising the steps of:

a. providing an Amycolatopsis strain derived from the Amycolatopsis Zyl 926 strain filed with the CABI Bioscience under the number IMI 390106, on 2 Mar. 2003, comprising at least one additional copy of the FCS gene encoding Feruloyl-CoA Synthetase having the sequence SEQ ID sequence NO: 1 or any sequence at least 80%, preferably at least 90%, and more preferably at least 95% identical to SEQ ID NO: 1 and encoding ECH Enoyl-coA Hydratase/Aldolase having the sequence SEQ ID NO: 2 or any sequence at least 80%, preferably at least 90%, and more preferably at least 95% identical to SEQ ID NO: 2 and that said additional copies are specifically incorporated at the φC31 phage integration site;

b. culturing the new Amycolatopsis strain derived from step a;

c. bringing ferulic acid into contact with said culture of Amycolatopsis strain of step b and incubating same;

d. extracting vanillin from the culture medium.

The cultivation of the new derived Amycolatopsis strains is preferably carried out on media containing all the nutrients needed for good growth of the bacteria, including a carbon source at temperatures and pH that are regulated in fermenters.

A source of carbon may be, for example, glycerol.

The incubation according to step c of vanillin production process is carried out until the consumption of substantially all of the ferulic acid and at a temperature between 37° C. and 41° C.

According to a particular embodiment of the invention, the vanillin production process is the process described in EP 1 611 244 A1.

The bioconversion reaction when vanillin production process is therefore carried out in a medium comprising a new Amycolatopsis sp. derived from the Amycolatopsis Zyl 926 strain according to the invention.

According to a particular embodiment of the invention, the Amycolatopsis strain derived from the Amycolatopsis Zyl 926 strain used in the vanilla production process in step a is selected from the strain filed with the CNCM under the number I-4922, the strain filed with the CNCM under the number I-4923 and the strain filed with the CNCM under the number I-4924.

The invention more particularly relates to a vanillin production process as described above wherein the molar yield is greater than or equal to 80%, preferably greater than or equal to 85%, and more preferably equal to 90%.

The invention more particularly relates to a vanillin production process as described above wherein at least 98% of ferulic acid is consumed, preferably at least 99%, and more preferably 100%.

The inventors implementing said vanillin production process as described above with the new Amycolatopsis strains of the invention have thus surprisingly noticed that:

• • almost all of the ferulic acid is consumed in the organic reaction conversion;
  • productivity is improved;
  • the molar yield is improved;

and this without the flow of vanillin dehydrogenase converting vanillin to vanillic acid being increased.

The present invention also relates to a new Amycolatopsis strain as described above in which the gene encoding vanillin dehydrogenase vdh is not removed.

The present invention also relates to a process for obtaining a novel Amycolatopsis strain as described above having no step of removing the vdh gene encoding vanillin dehydrogenase.

Material and Method

Bacterial strains:—Escherichia coli ET 12567

• • Amycolatopsis Zyl 926

Plasmids:—p SET152: carrying an ampicillin resistance gene

• • pUZ8002: carrying a gene for resistance to neomycin.

a. Amplification

The ECH and FCS genes were amplified from the Amycolatopsis Zyl 926 strain using the “Phusion® High-Fidelity PCR Master Mix with GC Buffer” kit with GC Buffer.

The primers used are:

b. Cloning

The fragment to be integrated is obtained by HindIII digestion (+ Klenow) and XbaI.

The HindIII fragment (+ Klenow) and XbaI was then cloned in the EcoRV and XbaI sites of pSET152. The plasmid thus obtained is called pLSF01a.

The pSET152 plasmid has the φC31 phage integration system namely:

• • the int gene encoding the integrase of the φC31 phage;
  • the attP attachment site of the φC31 phage;

The pSET152 plasmid also has the functional origin of transfer oriT allowing the mobilization thereof and transfer of E. coli to Amycolatopsis by the strain E. coli ET12567+pUZ8002.

b′. Amplification and Cloning of the ermE* Promoter

The addition of the ermE* promoter and the chloramphenicol resistance gene was carried out by in vivo recombination between short identical sequences (PCR-targeting) as described by Yu et al. (2000) (Proc Natl Acad Sci USA. 2000 23 May; 97 (11): 5978-83).

For this purpose, a sequence corresponding to the resistance gene for chloramphenicol, the ermE* promoter and the RBS of the tipA gene was obtained by PCR using as matrix the pOSV605 plasmid and as primers the oligonucleotides LG001 and LG002. The sequences of the primers used are following:

This yielded a fragment having at each end sequences identical to those of two neighbouring regions on the pLSF01a plasmid:

• • one in the part of the vector upstream of the ECH gene,
  • the other at the 5′ end of the ECH gene.

The recombination took place in vivo in the strain DY330 (Yu et al. 2000) containing the pLSF01 plasmid after transformation with the PCR product.

Clones that have integrated the ermE* promoter were selected on the basis of the acquisition of chloramphenicol resistance. Selected clones are called pLSF02 plasmids.

c. Transformation

The ET12567 strain containing the pUZ8002 plasmid was transformed by electroporation with the pLSF02 plasmid from steps b. and b′., comprising the additional copies of genes ECH and FCS and strong ermE* promoter associated with the RBS.

d. Selection of Transformants

Selecting transformants having the pLSF02 plasmid is done in a medium containing apramycin.

e. Interspecific Transfer

Amycolatopsis Zyl 926 cells are synchronized for germination by heating at 50° C. for 10 minutes.

Transformants (E. coli ET12567+pUZ8002+pLSF02) and the Amycolatopsis Zyl 926 cells thus prepared are then brought into contact by a co-culture for several hours to carry out the interspecific transfer.

f. Selection of Transformed Zyl 926 Strains

The selection of the Amycolatopsis Zyl 926 strains having integrated additional copies of ECH and FCS genes is done in a medium containing apramycin.

This last step has led to the selection of the strains deposited with the CNCM under the numbers I-4922, I-4923, I-4924 and have integrated additional copies of the ECH and FCS genes at the φC31 phage integration site.

Bacterial strains:—Escherichia coli ET 12567

• • Amycolatopsis Zyl 926

Plasmids:—pOSV408: carrying a gene for resistance to kanamycin.

• • pUZ8002: carrying a gene for resistance to neomycin.

a. Amplification

The ECH and FCS genes were amplified from the Amycolatopsis Zyl 926 strain using the “Phusion® High-Fidelity PCR Master Mix with GC Buffer” kit with GC Buffer

The primers used are:

b. Cloning

The fragment to be integrated is obtained by HindIII digestion (+ Klenow) and XbaI.

The HindIII fragment (+ Klenow) and XbaI was then cloned in the EcoRV and XbaI sites of pOSV408. The plasmid thus obtained is called pLSF01b

The pOSV408 plasmid (KanaR) has the integration system of the φBT1 phage namely:

• • the int gene encoding integrase of the φBTI phage;
  • the attP site of the φBTI attachment phage;

The pOSV408 plasmid also has the functional origin of transfer oriT allowing the mobilization thereof and transfer of E. coli to Amycolatopsis by the strain E. coli ET12567+pUZ8002.

b′. Amplification and Cloning of the ermE* Promoter

The addition of the ermE* promoter and the chloramphenicol resistance gene was carried out by in vivo recombination between short identical sequences (PCR-targeting) as described by Yu et al. (2000) (Proc Natl Acad Sci USA. 2000 May 23; 97 (11): 5978-83).

To this end, a sequence corresponding to the resistance gene for chloramphenicol, the ermE* promoter and for RBS of the tipA gene was obtained by PCR using as matrix the pOSV605 plasmid and as primers the LG001 and LG002 oligonucleotides having respectively the sequences SEQ ID NO: 9 and SEQ ID NO: 10.

This resulted in a fragment having at each end sequences identical to those of two neighbouring regions on the pLSFOlb plasmid:

• • one in the part of the vector upstream of the ECH gene,
  • the other to the 5′ end of the ECH gene.

The recombination took place in vivo in the DY330 strain (Yu et al. 2000) containing the pLSFOlb plasmid after transformation by the PCR product.

The clones which have integrated the ermE* promoter were selected on the basis of the acquisition of chloramphenicol resistance. The selected clones are called pLSF07 plasmids.

c. Transformation

The ET12567 strain containing the pUZ8002 plasmid is transformed by electroporation with the pLSF07 plasmid from the preceding steps, comprising the additional copies of the ECH and FCS genes and strong promoter ermE * associated with the RBS.

d. Selection of Transformants

Transformants which have integrated the pLSF07 plasmid are selected in a medium comprising kanamycin.

e. Interspecific Transfer

The cells of Amycolatopsis Zyl 926 are synchronized for germination by heating at 50° C. for 10 minutes.

The transformants and Amycolatopsis Zyl 926 cells thus prepared are then brought into contact by a co-culture for several hours to carry out the interspecific transfer.

f. Selecting Transformed Zyl 926 Strains

The strains Amycolatopsis Zyl 926 having integrated additional copies of the ECH and FCS genes are selected in a medium containing kanamycin.

This last step was used to select the strains filed with the CNCM on 11 Dec. 2014 under number I-4925, 1-4926 and I-4927 having integrated additional copies of the FCS and ECH genes at the φBTI phage integration site.

Bacterial strains:—CNCM-I-4922

• • Zyl 926

The vanillin production process used in this example is the process mentioned in EP 1 611 244 A1.

Maximum productivity is calculated using the following equation:

Concentrationofthevanillinproduced(g/Kg)Elapsedproductiontime(hours)

The molar yield is calculated according to the following equation:

100×vanillinmolarconcentrationferulicacidmolarconcentration

The overall mass yield of vanillin/ferulic acid is calculated according to the following equation:

100×vanillinmolarconcentrationferulicacidmassconcentration

The results obtained using the vanillin production process of EP 1 611 244 with the strain according to the invention I-4922 and the Zyl 926 strain are shown in Table 1 below.

Note that the density is close to 1, the unit g/kg is equivalent to g/L.

Conclusion

The results obtained show that the strain according to the invention I-4922 provides a greater amount of vanillin, an improved molar yield, and the consumption of substantially all of the ferulic acid based on the Zyl 926 strain of the prior art.

Bacterial strains:—CNCM-I-4922 (φC31)

• • CNCM-I-4926 (φBT1)
  • Zyl 926

The vanillin production process used in this example is the process mentioned of EP 1 611 244 A1.

The results obtained using the vanillin production process of EP 1 611 244 with the strains I-4922, 14926 and Zyl 926 are presented in Table 2 below.

The results show that the strain according to the invention I-4922 having integrated at least one copy of ECH and FCS genes at the φC31 phage integration site enables production of more vanillin compared to the strain of the prior art Zyl 926.

The results also show that the I-4926 strain having incorporated at least one extra copy of the FCS and ECH genes at the φBTI phage integration site does not improve the production of vanillin compared to the Zyl 926 strain of the prior art.

The integration of at least one additional copy of ECH and FCS genes of the invention in the Zyl 926 strain is locus dependent.