The present invention relates to a recombinant yeast cells and their use in the production of 3-hydroxypropionic acid (3-HP) .

Background Art

For more than a century, fossil fuels have been the primary feedstock for the chemical industries. However, new

discoveries of fossil fuel deposits are diminishing whilst demand for fossil fuel based chemicals are ever increasing, and soon the supply of fossil fuels will be outweighed by the demand. In an attempt to address this issue a large amount of effort has gone into developing novel biotechnological strategies for producing chemical feedstock from renewable sources (e.g. sugars) . In 2004 the Department of Energy in the USA identified a list of 12 target feedstock chemicals to be produced through biotechnological routes. 3-hydroxy propionic acid (3-HP) has been chosen as one of the 12 feedstock chemicals as it can serve as a platform for the development of a range of 3-carbon petrochemical

intermediates, and in particular it can be dehydrated to form acrylic acid. More than 1 billion kilograms of acrylic acid are produced annually as it is the monomeric building block for polymeric acrylates which can be used in a wide range of consumer products, e.g. personal care products, adhesives, coatings and paints, and the annual total market size is over USD100 billion. One particularly important application of 3- HP is for the production of superabsorbent polymers (SAP) , which constitute a significant part of baby diapers and incontinence products. It is evidently desirable to develop a more sustainable way of producing acrylic acid, hence this is why a significant amount of research continues towards the development of a biotechnological method of producing 3-HP, the acrylic acid precursor.

Conventional biological processes for producing 3-HP are performed by a complicated metabolic pathway. Therefore, it is difficult to control the process effectively, resulting in low production yield and productivity. For this reason it is necessary to design a 3-HP production pathway which controls the quantity of biochemical precursors in the cytosol such that the flux towards late stage biochemical intermediates in said 3-HP production pathway is favoured and alternative biological pathways are disfavoured.

EP 2505656 discloses a method of producing 3-HP using a malonic semialdehyde reducing pathway, wherein the process utilises an NADPH dependent malonyl-CoA reductase which may be derived from C. aurantiacus and an NADP/NADPH dependent GAPDH variant to resolve a redox imbalance within the

metabolic process. The maximum reported yield of 3-HP was approximately 1.3 g/L. Rathnasingh et al . (J. Biotechnol. 2012) discloses a method of producing 3-HP using Escherichia coli cells, wherein said cells overexpress MCR from C. aurantiacus and ACC in the malonyl-CoA pathway. The maximum reported yield of 3-HP was 2.14 mmol/L (0.19 g/L) . WO 2008/080124 discloses a method of producing butanol using modified yeast, wherein said method produces increased quantities of cytosolic acetyl-CoA by overexpressing PDC1 and ALD6 which may be derived from S. cerevisiae and ACS which may be derived from S. entherica . This method does not utilise the malonyl-CoA pathway. WO 2007/024718 discloses a method of producing isoprenoid compounds using genetically modified host cells, wherein said cells are modified to produce increased levels of acetyl-CoA by increasing ALD and ACS activity. This method does not utilise the malonyl-CoA pathway.

In S. cerevisiae, acetyl-CoA carboxylase is tightly regulated at the transcriptional, translational and post-translational levels (Shirra, M.K. et al, 2001; Nielsen, J. 2009) . At the level of the protein, Snfl kinase is the major kinase which phosphorylates and inactivates ACC1 in vivo (Shirra, M.K. et al, 2001) . WO 2012/017083 discloses a method of producing wax esters using modified yeast, wherein the quantity of

cytosolic acetyl-CoA is increased through increasing the activity of ACC1 by mutating ACC1 at dephosphorylation sites such that it is no longer inactivated by Snfl.

Description of the Invention

The present invention relates to a recombinant yeast cell which produces high supernatant concentrations (up to 10 g/L) of 3-HP by increasing the flux towards cytosolic malonyl-CoA, which is reduced to 3-HP by malonyl-CoA reductase (MCR) . The recombinant yeast cell overexpresses pyruvate decarboxylase (PDC) , aldehyde dehydrogenase (ALD) , Acetyl-CoA synthase (ACS), and a mutated Acetyl-CoA Carboxylase (ACC*) (the enzyme is mutated at two dephosphorylation sites to prevent inactivation by Snfl) which increases the conversion of pyruvate to malonyl-CoA. MCR derived from Chloroflexus aurantiacus reduces malonyl-CoA to 3-HP using NADPH as a cofactor. In order to resolve the resulting redox imbalance within the metabolic process the endogenous NAD dependent glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is replaced with with an NADP dependent GAPDH variant. None of the above cited art discloses the specific combination of the features of the herein described

invention. Furthermore, the recombinant yeast of present invention produces 3-HP in substantially greater yields than the cited art.

In a first aspect the present invention relates to a yeast cell for use in producing 3-hydroxypropionic acid (3-HP) , wherein said yeast cell incorporates genetic modification such that said cell expresses the enzymes:

- Pyruvate decarboxylase (PDC)

- Aldehyde dehydrogenase (ALD)

- Acetyl-CoA synthase (ACS)

- Acetyl-CoA carboxylase (ACC*) mutated in at least one dephosphorylation site to prevent inactivation by Snfl - Malonyl-CoA reductase (MCR) ,

said cell has a reduced level of activity of NAD dependent glyceraldehyde-3-phosphate dehydrogenase (GAPDH) , suitably by virtue of deletion, attenuation, disruption, down-regulation, or mutation of one or more genes expressing NAD dependent GAPDH and has at least one exogenous gene encoding NADP dependent GAPDH and/or has up-regulation of at least one endogenous gene expressing NADP dependent GAPDH. It has been found that combined expression of the enzymes NADP dependent GAPDH, PDC, ALD, ACS, ACC* and MCR in said host cell

increases metabolic flux towards 3-HP via malonyl-CoA

compared to an otherwise similar yeast cell lacking said genetic modification.

In a preferred embodiment of the invention the recombinant yeast strain comprises one or more exogenous nucleic acid molecules encoding at least one of PDC, ALD, ACS, ACC* and/or MCR. Preferably, said nucleic acid molecule is expressed from multiple integrations of said nucleic acid molecule in the host cell genome. Such a multiply integrated nucleic acid molecule may encode, for example, MCR.

The nucleic acid molecule encoding PDC may be derived from Saccharomyces cerevisiae. ^λ Derived from' is used herein to specify the species from which the original genetic material encoding the specified enzyme originated.

The nucleic acid molecule encoding ALD may be derived from Saccharomyces cerevisiae . The nucleic acid molecule encoding ACS may be derived from Salmonella enterica.

The ACC* enzyme may be mutated in at least two

dephosphorylation positions in the enzyme. In a preferred embodiment, the ACC* enzyme is mutated at amino acid

positions Ser659 and Serll57. Suitably Ser659 and Serll57 are replaced by amino acids comprising side chains which are incapable of being phosphorylated, preferably Ala, Val, Leu, lie, Pro, Phe, Trp and/or Met. The nucleic acid molecule encoding the non-mutated version of the ACC* enzyme may be derived from Saccharomyces cerevisiae .

The nucleic acid molecule encoding MCR may be derived from Chloroflexus aurantiacus .

The nucleic acid molecule encoding NADP dependent GAPDH may be derived from Clostridium acetobutylicum, Kluyveromyces lactis or Bacillus subtilis .

In another aspect, the present invention relates to a method for producing 3-HP, said method comprising culturing yeast cells as described herein under conditions such that 3-HP is produced . In a preferred embodiment of the invention, the yeast cells are cultured on a medium comprising at least one carbon substrate, wherein said carbon substrate may be glucose or galactose . Preferably, culturing said yeast cells on a medium comprising at least one carbon substrate produces a supernatant

concentration of at least 5 g/L 3-HP, more preferably said yeast cells produce a supernatant concentration of at least 6 g/L 3-HP, more preferably said yeast cells produce a

supernatant concentration of at least 7 g/L 3-HP, more preferably said yeast cells produce a supernatant

concentration of at least 8 g/L 3-HP, and most preferably said yeast cells produce a supernatant concentration of at least 9 g/L 3-HP. In another preferred embodiment of the invention, said method further comprises isolating 3-HP produced by said recombinant yeast strain.

Figures

Figure 1: Bar chart comparing yeast cells transformed with ACC comprising zero, one or two mutations at

dephosphorylation sites.

Figure 2 : Bar chart comparing the supernatant concentration of 3-HP produced by yeast cells transformed with a multicopy vector, a single integrative vector and a multiple

integrative vector.

Figure 3: Bar chart comparing the supernatant concentration of 3-HP produced by yeast cells overexpressing ACS, ALD6 and/or PDC1 in both DELFT and FIT media. Figure 4 : Bar chart comparing the supernatant concentration of 3-HP produced by yeast cells with increased pool of available NADPH and those with no increased pool of available NADPH. Figure 5: Bar chart demonstrating the effect of replacing the coding sequence of endogenous NAD dependent GAPDH with NADP dependent GAPDH on supernatant concentration of 3-HP in both DELFT and FIT media.

Figure 6: Bar chart comparing the supernatant concentration of 3-HP produced by yeast cells with improved NADPH supply in DELFT and FIT media.

Figure 7: Graph showing the supernatant concentration of 3- HP, glucose, glycerol, acetate and ethanol vs time in an N and C limited fed batch fermentation of highest producing yeast strain ST687

Figure 8: Graph showing the supernatant concentration of 3- HP, glucose, glycerol, acetate and ethanol vs time in a C limited fed batch fermentation of the highest producing yeast strain ST687

Oligonucleotide sequences

Table 2. Primers and templates used to generate gene fragments for USER cloning and yeast transformation by PCR

Table 3. Plasmids

Table 4. Yeast strains

Example 1. Cloning of over-expression targets into expression plasmids .

All plasmids listed in table 3 were generated by USER cloning using PCR generated gene fragments, which were amplified according to table 2. The typical USER reaction was as follows: 1 μΐ of linearized and nicked parent plasmid was mixed with 1 μΐ of promoter fragment, 2 μΐ of gene fragment, 0.5 μΐ Taq polymerase buffer, 0.5 μΐ USER enzyme (NEB) . The mix was incubated at 37°C for 25 min, at 25°C for 25 min and transformed into chemically competent E. coli DH5alpha. The clones with correct inserts were identified by colony PCR and the plasmids were isolated from overnight E. coli cultures and confirmed by sequencing.

The expression plasmids were transformed into S. cerevisiae cells using the lithium acetate transformation protocol. The cells were selected on synthetic complete (SC) agar medium without uracil, histidine and leucine.

Example 2. ACC1** Engineering acetyl-CoA carboxylase for improving the production of 3-hydroxypropionic acid

Ser659 and Serll57 of ACC1 were identified as two putative phosphorylation sites according to the phosphorylation recognition motif (Hyd-X-Arg-XX-Ser-XXX-Hyd) for yeast Snfl (Dale, S. et al, 1995) . One of which, Serll57 was verified by a phosphoproteome study (Ficarro, S. et al, 2002). Ser659 has not been reported through experimental data so far.

Therefore, we have constructed mutated ACC1 with either one or two assumed phosphorylation sites.

The endogenous ACC1 gene (wild-type) encoding acetyl-CoA carboxylase was amplified from genomic DNA of CEN. PK.113-5D by PCR with Phusion high-fidelity polymerase. The primers are sted in Table 1. The single mutatation ACClSerll57Ala and double mutation ACCl Ser659Ala, Serll57Ala were introduced by

oligonucleotide primers. Three versions of ACCl were digested with Notl and Sacl, and then ligated into the corresponding sites of pSP-GM2 (Chen et al . , 2012), resulting in plasmid pAW (containing wild-type ACCl), pAS (containing single mutated ACCl) and pAD (containing double mutated ACCl), respectively .

For re-constructing the pathway for 3-HP production, the gene CaMCR encoding malonyl-CoA reductase from Chloroflexus aurantiacus was codon optimized for expression in yeast and synthesized by GenScript (Piscataway, NJ, USA) . CaMCR was cloned into pIYC04 (Chen et al . , 2013) using the BamHI and Xhol cloning sites downstream of the TEFl promoter, resulting in plasmid pYC6. To evaluate the effect of engineered ACCl on 3-HP production, plasmids combinations pSP-GM2 / pYC6, pAW / pYC6, pAS / pYC6 and pAD / pYC6 were transformed into CEN.PK 113-llC to construct yeast recombinant strain HPY15 to HPY18, respectively . For the cultivation of yeast recombinant strains, 20 ml cultures in 100 ml unbaffled cotton-stopped flasks were inoculated with an amount of pre-culture that resulted in a final optical density of 0.02 at 600 nm (OD600) . The strains were grown at 30 °C with 180 r.p.m. orbital shaking in defined minimal medium with 20 g l ^"1 glucose as described before (Chen et al . , 2013) . Samples were taken periodically to measure the cell mass, concentration of 3-HP, residual glucose and other metabolites.

The results are shown in figure 1. Overexpression of wild- type ACCl HPY16 increased 3-HP production by 60%, compared to the reference strain HPY15. Overexpression of mutated ACCl by blocking the phosphorylation sites, HPY17 and HPY18, further enhanced the production of 3-HP. Double mutated ACCl ^Ser659Ala ' serii57Aia fjpy]_g g _ave the highest improvement, around threefold, relevant to that of the reference strain. Example 3. Production of 3HP in S. cerevisiae by over- expression of CaMCR and ACCl** from multiple integration plasmids

CEN.PK102-5D was transformed with either episomal multicopy plasmid p298, or single integrative plasmid p343, or multiple integration plasmid p376. All three plasmids tested harboured ACCl** and CaMCR. Four single transformants for each plasmid tested were inoculated in 0.5 ml SC ura- in a 96-deep well microtiter plate with air-penetrable lid (EnzyScreen) . The plates were incubated at 30°C with 250 rpm agitation at 5 cm orbit cast overnight. 50 μΐ of the overnight cultures were used to inoculate 0.5 ml Delft medium (Delft medium described in WO 2011/147818) in a 96-deep well plate and 0.5 ml FIT Fed-batch-media (M2P labs) . Fermentation was carried out for 72 hours at the same conditions as above. At the end of the cultivation the OD ₆₀₀ was measured. 10 μΐ of the sample was mixed with 190 μΐ water and absorbance was measured at 600 nm wave length in a spectrophotometer

(BioTek) .

The culture broth was spun down and the supernatant analyzed for 3-hydroxypropionic acid concentration using enzymatic assay, which was performed as follows: 20 μΐ of standards (3HP at concentrations from 0.03 to 1 g/L in Delft medium) and samples were added to a 96-well flat bottom transparent plate (Greiner) . 180 μΐ of mix (14.8 ml water, 2 ml buffer (1 mM Tris, 25 mM MgCl ₂ , pH 8.8), 1 ml NADP+ solution (50 mg/ml) , and 0.2 ml purified YdfG enzyme in PBS buffer (1500 yg/ml) ) was added per well using a multichannel pipette. The start absorbance at 340 nm was measured and the plate was sealed and incubated at 30°C for 1.5 hours. After incubation the absorbance at 340 nm was measured again. The difference between the end and the start values corrected for the background were in linear correlation with 3HP

concentrations. The concentration of 3HP in each sample was calculated from the standard curve. Expression of ACC1** and CaMCR from the multiple integration plasmid p376 led to a 5 times improvement of 3HP production in the best clone, when compared to a S. cerevisiae strain bearing a single integrative vector with the same genes

(figure 2 ) . Example 4. Improving 3HP production in S. cerevisiae by increasing the precursor supply towards Acetyl-CoA

Strains harbouring either p380-ALD6-ACS or p380-ALD6-ACS in combination with p382-PDCl were transformed with p474-CaMCR- ACC1**. A minimum of 6 clones were picked, fermented and tested for 3HP production by enzymatic assay as in example 2 (figure 3) . The best producer of strains having p380-ALD6-ACS in combination with p474-CaMCR-ACCl** gave up to 1.5 fold higher 3HP titer than the wild type (WT) strain with p474- CaMCR-ACCl * * , and strains with all three plasmids combined gave up to 2.5 times more than the WT background in both DELFT and FIT media.

Example 5. Effect of Increasing the pool of available NADPH on the production of 3-hydroxypropionic acid

The effect of increasing NADPH supply on the production of 3- hydroxypropionic acid was tested. The gapN gene from Streptococcus mutants, which encodes non-phosphorylating NADP-dependent glyceraldehyde-3-phosphate dehydrogenase, was codon optimized and synthesized by GeneScript (Piscataway, NJ, USA). The gene gapN was cloned into pIYC04 (Chen et al . , 2013) using the restriction sites Notl and Sacl, resulting in plasmid pJC2. Plasmids pJC2 and pYCl were transformed into CEN.PK 113-llC, forming the recombinant yeast strain HPY09. It was found that the over-expression of gapN alone resulted in a final titer of 122 mg l ^-1 3-HP, which is a 30%

improvement compared to the reference strain (figure 4) .

Example 6. Construction of strain with improved NADPH supply

An elevated level of NADPH was achieved by overexpression of an NADP dependent glyceraldehyde-3-phosphate dehydrogenase gene from either Clostridium acetobutylicum, CaGAPDH (Seq ID NO 08), Kluyveromyces lactis, K1GAPDH (Seq ID NO 9), or

Bacillus subtilis, BsGapB (Seq ID NO 10) . The NADP dependent GAPDH was expressed in yeast strains, where one, two or three of the endogenous NAD dependent glyceraldehyde-3-phosphate dehydrogenase genes TDH1-3 were deleted and/or exchanged with the CDS of GAPDH. By exchanging the CDS we aimed to ensure that the introduced GAPDH had the same expression profile as the endogenous NAD dependent GAPDH. Additionally, any

potential futile cycling between the endogenous GAPDH and the introduced GAPDH was avoided by removing or lowering the level of endogenous GAPDH activity. Eight different

combinations were made according to Table 4. Each of those eight strains and a WT strain were all transformed with p380- ALD6-ACS in combination with p382-PDCl and p474-CaMCR-ACCl** . A minimum of 12 clones for each strain were tested for 3HP production as in example 2 (figure 5) . In both media tested, there was a significant increase in 3HP yield for the strains where TDH3 was replaced with CaGAPDH. However, there was no further effect when this exchange was combined with any of the other CDS exchanges. The three best producers for the WT and the tdh3 :: CaGAPDH strains were analyzed further by HPLC (figure 6). The ^X WT' strains gave 1.46 ±0.14 g/1 and 3.31 ±0.34 g/1 3HP in DELFT and FIT, respectively. The

xtdh3 :: CaGAPDH' strains gave 2.01 ±0.01 g/1 and 5.10 ±0.22 g/1 3HP in DELFT and FIT, respectively. Furthermore, the ratio between 3HP formed and glycerol formed was higher for the tdh3 :: CaGAPDH strains in both media tested.

The best producer among the tdh3 :: CaGAPDH strains was named ST687 and was used in future fermentation experiments.

Example 7. Fermentations of high producing strain (ST687)

Strain ST687 was fermented under two different fermentation regimes; 1, N and C limited fed batch, and 2, C limited fed batch .

batch with 0.5L, then

Working batch with 0.5L, then fill up fill up to 1 L during

volume to 1 L during fed-batch

fed-batch

800 rpm (variable in the fed-

Agitation 800 rpm

batch phase)

1 vvm (1 L/min) (variable in

Aeration 1 vvm (1 L/min)

the fed-batch phase)

Aeration gas Air Air

Fermentation

70 hours 120 hours

lengh

Sampling

2-3 times a day 2 times a day

frequency

The inoculum was prepared as follows. A stock tube of ST/687 was inoculated into 50 ml SC-ura-his-leu and grown overnight at 30°C. 400 ml fresh medium is added and divided into 3

flasks, 150 ml in each and grown overnight at 30°C. The

cultures from overnight shake flasks is combined to obtain a total of about 450 ml, which then is poured into 6x50ml

Falcon tubes. Tubes are spun 4,000xg for 2 min and

supernatant is discarded. The rest of the overnight culture is added to the 6 tubes (about 25 ml/tube), resuspended, and pooled into 2 tubes into one to end up with 3 tubes.

Inoculate 1 tube per reactor.

Each sample was analyzed by HPLC as in example 4. The results are summarized in table below and in figures 7 and 8. N and C C limited

limited

Titers (3-HP) 9.5 g/L 9.83 ± 0.43 g/L

Prod. Rate in fed batch 0.20 g/L/h 0.09 ± 0.01 g/L/h phase

Specific yield, g/g DW 1.01 g/g DW 0.69 ± 0.05 g/g DW

Overall yield, % C-mol/C- 18 % 13 ± 1 %

mol glucose

Both fermentations involving the best 3-HP producing yeast strain ST687 produced supernatant concentrations of >9 g/L 3- HP. This is a significant increase over the supernatant concentrations disclosed in the prior art.

References

Chen, Y., Partow, S., Scalcinati, G., Siewers, V., Nielsen, J. Enhancing the copy number of episomal plasmids in Saccharomyces cerevisiae for improved protein production. FEMS Yeast Res. 12, 598-607 (2012).

Chen, Y., Daviet, L., Schalk, M., Siewers, V., Nielsen, J. Establishing a platform cell factory through engineering of yeast acetyl-CoA metabolism. Metab Eng. 15, 48-54 (2013). Dale, S., Wilson, W.A., Edelman, A.M. & Hardie, D.G. Similar substrate recognition motifs for mammalian AMP-activated protein kinase, higher plant HMG-CoA reductase kinase-A, yeast SNF1, and mammalian calmodulin-dependent protein kinase I. FEBS Letters 361, 191-195 (1995). Ficarro, S. et al . Phosphoproteome analysis by mass

spectrometry and its application to Saccharomyces cerevisiae. Nat Biotechnol 20, 301-305 (2002) .

Nielsen, J. Systems biology of lipid metabolism: From yeast to human. FEBS Letters 583, 3905-3913 (2009) . Rathnasingh, C, Raj, S. M., Lee, Y., Catherine, C, Ashok, S., Park, S., J. Production of 3-hydroxypropionic acid via malonyl-CoA pathway using recombinant Escherichia coli strains. J. Biotechnol., 633-640 (2012).

Shirra, M.K. et al . Inhibition of Acetyl Coenzyme A

Carboxylase Activity Restores Expression of the INOl Gene in a snfl Mutant Strain of Saccharomyces cerevisiae. Mol. Cell. Biol. 21, 5710-5722 (2001). In this specification, unless expressly otherwise indicated, the word 'or' is used in the sense of an operator that returns a true value when either or both of the stated conditions is met, as opposed to the operator 'exclusive or' which requires that only one of the conditions is met. The word 'comprising' is used in the sense of 'including' rather than in to mean 'consisting of . All prior teachings

acknowledged above are hereby incorporated by reference. No acknowledgement of any prior published document herein should be taken to be an admission or representation that the teaching thereof was common general knowledge in Australia or elsewhere at the date hereof.

The invention may be summarised according to the following clauses:

1. A yeast cell for use in producing 3-hydroxypropionic acid (3-HP) , wherein said yeast cell incorporates genetic modification such that said cell expresses the enzymes: - Pyruvate decarboxylase (PDC)

Aldehyde dehydrogenase (ALD)

Acetyl-CoA synthase (ACS)

Acetyl-CoA carboxylase (ACC*) mutated in at least one dephosphorylation site to prevent inactivation by Snfl

- Malonyl-CoA reductase (MCR) , said cell has a reduced level of activity of NAD dependent glyceraldehyde-3-phosphate dehydrogenase (GAPDH) by virtue of deletion, attenuation, disruption, down-regulation, or mutation of one or more genes expressing NAD dependent GAPDH and has at least one exogenous gene encoding NADP dependent GAPDH and/or has up-regulation of at least one endogenous gene expressing NADP dependent GAPDH, and wherein combined expression of the enzymes NADP dependent GAPDH, PDC, ALD, ACS, ACC* and MCR in said host cell

increases metabolic flux towards 3-HP via malonyl-CoA

compared to an otherwise similar yeast cell lacking said genetic modification.

2. A yeast cell as defined in clause 1, comprising one or more exogenous nucleic acid molecules encoding at least one of PDC, ALD, ACS, ACC* and/or MCR.

3. A yeast cell as defined in clause 2, wherein a said nucleic acid molecule is expressed from multiple integrations of said nucleic acid molecule in the host cell genome.

4. A yeast cell as defined in clause 2, wherein a nucleic acid molecule encoding PDC is derived from Saccharomyces cerevisiae .

5. A yeast cell as defined in clause 2, wherein the nucleic acid molecule encoding ALD is derived from Saccharomyces cerevisiae . 6. A yeast cell as defined in clause 2, wherein a nucleic acid molecule encoding ACS is derived from Salmonella

entherica .

7. A yeast cell as defined in clause 2, wherein a ACC* enzyme is mutated in at least two dephosphorylation positions in the enzyme.

8. A yeast cell as defined in clause 7, wherein the ACC* enzyme is mutated at amino acid positions Ser659 and Serll57, wherein Ser659 and Serll57 are replaced by amino acids comprising side chains which are incapable of being phosphorylated .

9. A yeast cell as defined in clause 8, wherein said amino acids comprising side chains which are incapable of being phosphorylated are Ala, Val, Leu, lie, Pro, Phe, Trp, Met.

10. A yeast cell as defined in clause 8, wherein the nucleic acid molecule encoding the non-mutated version of the ACC* enzyme is derived from Saccharomyces cerevisiae .

11. A yeast cell as defined in clause 2, wherein a nucleic acid molecule encoding MCR is derived from Chloroflexus aurantiacus .

12. A yeast cell as defined in clause 1, wherein a nucleic acid molecule encoding NADP dependent GAPDH is derived from Clostridium acetobutylicum, Kluyveromyces lactis or Bacillus subtilis .

13. A method for producing 3-HP, said method comprising culturing yeast cells as claimed in any of the preceding claims under conditions such that 3-HP is produced.

14. A method as defined in clause 13, wherein said yeast cells are cultured on a medium comprising at least one carbon substrate .

15. A method as defined in clause 14, wherein said carbon substrate is glucose, xylose, arabinose, or galactose.

16. A method as defined in clause 13, wherein said yeast cells produce a supernatant concentration of at least 5 g/L

3-HP. 17. A method as defined in clause 13, wherein said yeast cells produce a supernatant concentration of at least 6 g/L 3-HP.

18. A method as defined in clause 13, wherein said yeast cells produce a supernatant concentration of at least 7 g/L 3-HP.

19. A method as defined in clause 13, wherein said yeast cells produce a supernatant concentration of at least 8 g/L 3-HP.

20. A method as defined in clause 13, wherein said yeast cells produce a supernatant concentration of at least 9 g/L 3-HP. n

21. A method as defined in clause 13, wherein said method further comprises isolating 3-HP produced by said yeast cells.