Yeast cells for glycerol free ethanol production
The invention relates to a recombinant yeast comprising a nucleotide sequence allowing the expression of a glucoamylasey (EC 3.2.1.20 or 3.2.1.3). This cell can be used for the production of ethanol and advantageously produces little or no glycerol.
1. A recombinant yeast comprising:
a nucleotide sequence encoding a glucoamylase comprising an amino acid sequence that has at least 70% sequence identity to the amino acid sequence of SEQ ID NO:17.
2. The recombinant yeast according to claim 1 further comprising:
a nucleotide sequence coding for a glycerol dehydrogenase.
3. The recombinant yeast according to claim 1 further comprising:
a nucleotide sequence coding for a ribulose-1,5-biphosphate carboxylase oxygenase (EC 4.1.1.39, RuBisCO); and
a nucleotide sequence coding for a phosphoribulokinase (EC 2.7.1.19, PRK).
4. The recombinant yeast according to claim 1 further comprising a nucleotide sequence coding for a glycerol transporter.
5. The recombinant yeast according to claim 1 which comprises a deletion or disruption of one or more endogenous nucleotide sequences encoding a glycerol exporter.
6. The recombinant yeast according to claim 1 which comprises a deletion or disruption of one or more endogenous nucleotide sequences encoding a glycerol kinase (EC 2.7.1.30).
7. The recombinant yeast according to claim 1 which comprises a deletion or disruption of one or more endogenous nucleotide sequences encoding a glycerol-3-phosphate dehydrogenase (GPD1/2).
8. The recombinant yeast according to claim 1 which comprises a deletion or disruption of one or more endogenous nucleotide sequences encoding a glycerol 3-phosphate phosphohydrolase (GPP 1/2).
9. The recombinant yeast according to claim 1 which is a Saccharomyces , optionally Saccharomyces cerevisiae.
10. The recombinant yeast according to claim 1 further comprising one or more nucleotide sequences encoding a polypeptide comprising an amino acid sequence selected from the group consisting of SEQ ID NO:9, SEQ ID NO:10, functional homologues of SEQ ID NO:9, and functional homologues of SEQ ID NO:10.
11. A product comprising the recombinant yeast according to claim 1 for the preparation of ethanol and/or succinic acid.
12. A process for production of ethanol comprising:
fermenting a composition comprising a fermentable carbohydrate under anaerobic conditions in the presence of a recombinant yeast according to claim 1 , wherein said fermentable carbohydrate optionally is selected from the group consisting of glucose, fructose, sucrose, maltose, xylose, arabinose, galactose, and mannose; and
recovering ethanol.
13. The process according to claim 12 wherein fermentable carbohydrate is obtained from starch, lignocellulose, and/or pectin.
14. The process according to claim 12 wherein said composition further comprises undissociated acetic acid in an amount of 10 mM or less.
15. The process according to claim 12 wherein said composition further comprises undissociated acetic acid in an amount of between 50 μM and 10 mM.
16. The process according to claim 12 which further comprises adding glucoamylase at a concentration of 0.05 g/L or less.