Cells with improved pentose conversion

Abstract

The invention relates to a cell capable of converting one or more pentose sugar and one or more hexose sugar into fermentation product constitutively expressing one or more heterologous or homologous polypeptide having the amino acid sequence set out in SEQ ID NO: 20, or a variant polypeptide thereof having at least 45% identity to SEQ ID NO 20. In an embodiment the heterologous polypeptide has glyoxalase activity.

1 . A cell capable of converting one or more pentose sugar and one or more hexose sugar into fermentation product constitutively expressing one or more heterologous or homologous polypeptide having the amino acid sequence set out in SEQ ID NO: 20 or a variant polypeptide thereof, having at least 45% identity to SEQ ID NO 20. 
     
     
         2 . A cell according to  claim 1 , wherein the heterologous polypeptide has glyoxalase activity, optionally comprising glyoxalase I activity. 
     
     
         3 . An cell capable of converting one or more pentose sugar and or one or more hexose sugar into fermentation product comprising a constitutively expressed heterologous or homologous polynucleotide which comprises:
 (a) the nucleotide sequence as set out in SEQ ID NO: 27;   (b) a nucleotide sequence having at least about 50% sequence identity with the nucleotide sequence of SEQ ID NO: 27;   (c) a fragment of a nucleotide sequence as defined in (a), (b) or (c) having at least 100 nucleotides;   (d) a sequence which is degenerate as a result of the genetic code to a sequence as defined in any one of (a), (b), or (c);   (e) a nucleotide sequence which is the reverse complement of a nucleotide sequence as defined in (a), (b), (c), or (d).   
     
     
         4 . A cell according to  claim 1 , comprising a nucleotide sequence encoding a xylose isomerase. 
     
     
         5 . A cell according to  claim 1 , wherein the cell comprises one or more genetic modifications resulting in:
 (a) an increase in transport of xylose in the cell;   (b) an increase in xylulose kinase activity;   (c) an increase in flux through the pentose phosphate pathway;   (d) a decrease in aldose reductase activity;   (e) a decrease in sensitivity to catabolite repression;   (f) an increase in tolerance to ethanol, osmolarity or organic acid; or   (g) a reduced production of by-product.   
     
     
         6 . A cell according to  claim 5 , wherein the one or more genetic modifications result in overexpression of at least one gene encoding an enzyme of the non-oxidative part of the pentose phosphate pathway. 
     
     
         7 . A cell according to  claim 6 , wherein the gene is a gene encoding a ribulose-5-phosphate isomerase, a ribulose-5-phosphate epimerase, a transketolase or a transaldolase. 
     
     
         8 . A cell according to  claim 5 , wherein the one or more genetic modifications result in overexpression of a gene encoding a xylulose kinase. 
     
     
         9 . A cell according to  claim 5 , wherein the one or more genetic modifications result in a decrease in aldose reductase activity in the cell. 
     
     
         10 . A cell according to  claim 5  which has the ability to use L-arabinose, wherein the genes TAL1, TKL1, RPE1 and RKI1 are overexpressed. 
     
     
         11 . A cell according to  claim 1 , wherein the coding region of the GRE3-gene is inactivated by replacement of the coding region with a nucleotide sequence comprising the genes TAL1, TKL1, RPE1 and RKI1. 
     
     
         12 . A cell according to  claim 1 , wherein the genes araA, araB and araD are expressed. 
     
     
         13 . A cell according to  claim 1 , wherein one or more constitutively expressed or constitutively overexpressed genes are stably integrated into the genome of the cell. 
     
     
         14 . A process for producing a fermentation product which process comprises fermenting a medium comprising a source of xylose and/or arabinose with a cell according to  claim 1  such that the cell ferments xylose and/or to the fermentation product. 
     
     
         15 . A process according to  claim 14 , wherein the fermentation product is chosen from the list including ethanol, butanol, lactic acid, 3-hydroxy-propionic acid, acrylic acid, acetic acid, succinic acid, citric acid, malic acid, fumaric acid, itaconic acid, an amino acid, 1,3-propane-diol, ethylene, glycerol, butanol, a β-lactam antibiotic and a cephalosporin. 
     
     
         16 . A process according to  claim 15  wherein the fermentation product is ethanol. 
     
     
         17 . A process according to  claim 14 , wherein the process is anaerobic.