Microbial conversion of sugar acids and means therein

Abstract

A DNA molecule comprising a fungal gene encoding an enzyme protein capable of converting L-galactonic acid into L-threo-3-deoxy-hexulosonic acid has been cloned and heterologously expressed. The enzyme is involved in the metabolic conversion of sugar acids, which are present in biological waste material such as sugar beet pulp and other pectin comprising material. A microorganism genetically modified to effectively express said enzyme may be used in fermenting biomaterial to desired end products such as ethanol. Alternatively, microorganisms in which the gene has been inactivated may be used to produce L-galactonic acid, which accumulates when the expression of the gene is prevented.

1 . An isolated DNA molecule comprising a gene encoding an enzyme protein capable of converting L-galactonic acid into L-threo-3-deoxy-hexulosonic acid. 
     
     
         2 . The DNA molecule according to  claim 1 , wherein said DNA encodes an enzyme protein comprising the amino acid sequence of SEQ ID NO: 2 or a functional equivalent thereof. 
     
     
         3 . The DNA molecule according to  claim 1 , wherein said DNA encodes an L-galactonic acid dehydratase of fungal origin. 
     
     
         4 . The DNA molecule according to  claim 1 , wherein said gene comprises the nucleic acid sequence of SEQ ID NO: 1, or a functional equivalent thereof. 
     
     
         5 . A genetically engineered DNA molecule comprising the DNA molecule according to  claim 1 . 
     
     
         6 . A genetically modified microorganism transformed with the genetically engineered DNA molecule according to  claim 5 . 
     
     
         7 . The genetically modified microorganism according to  claim 6 , said microorganism being deposited under accession number DSM 17214. 
     
     
         8 . An enzyme protein capable of converting L-galactonic acid into L-threo-3-deoxy-hexulosonic acid. 
     
     
         9 . The enzyme protein according to  claim 8  comprising the amino acid sequence of SEQ ID NO: 2 or a functional equivalent thereof. 
     
     
         10 . The enzyme protein according to  claim 8 , said protein being further capable of converting D-arabonic acid to D-glycero-3-deoxy-pentulosonic acid. 
     
     
         11 . A method of producing an enzyme protein capable of converting L-galactonic acid into L-threo-3-deoxy-hexulosonic acid, said method comprising cultivating the microorganism of  claim 6  under conditions allowing expression of said protein, and recovering the enzyme protein. 
     
     
         12 . A method of converting L-galactonic acid to L-threo-3-deoxy-hexulosonic acid comprising contacting L-galactonic acid with the enzyme protein according to  claim 8 . 
     
     
         13 . The method according to  claim 12  for producing a desired compound from biomass comprising a sugar acid, said method comprising the steps of
 transforming a host microorganism with a DNA molecule comprising a gene encoding an enzyme protein capable of converting L-galactonic acid into L-threo-3-deoxy-hexulosonic acid,   fermenting said biomass with the transformed microorganism, and   recovering the desired compound produced.   
     
     
         14 . The method according to  claim 13 , comprising fermenting sugar beet pulp or another pectin comprising material, and recovering ethanol, lactic acid, or other compounds derived from pyruvic acid from the fermentation. 
     
     
         15 . A method of converting D-arabonic acid to D-glycero-3-deoxy-pentulosonic acid comprising contacting D-arabonic acid with the enzyme protein according to  claim 10 . 
     
     
         16 . Use of the enzyme protein according to  claim 8  for producing a desired compound from a material comprising a sugar acid or a derivative thereof. 
     
     
         17 . An enzyme preparation comprising the enzyme protein of  claim 8 . 
     
     
         18 . A genetically modified microorganism, wherein a gene encoding an enzyme protein capable of converting L-galactonic acid into L-threo-3-deoxy-hexulosonic acid has been inactivated. 
     
     
         19 . A method of producing L-galactonic acid using the genetically modified microorganism according to  claim 18 . 
     
     
         20 . A method of producing D-arabonic acid using the genetically modified microorganism according to  claim 18 .