L-arabinose fermenting yeast

Abstract

An L-arabinose utilizing yeast strain is provided for the production of ethanol by introducing and expressing bacterial araA, araB and araD genes, L-arabinose transporters are also introduced into the yeast to enhance the uptake of arabinose. The yeast carries additional genomic mutations enabling it to consume L-arabinose, even as the only carbon source, and to produce ethanol. A yeast strain engineered to metabolize arabinose through a novel pathway is also disclosed. Methods of producing ethanol include utilizing these modified yeast strains.

1 - 37 . (canceled) 
     
     
         38 . A transgenic yeast strain for fermenting arabinose to ethanol, the transgenic yeast strain comprising genes for the expression of an araA peptide, an araB peptide and an araD peptide and wherein the transgenic strain is aldose reductase deficient (AR − ). 
     
     
         39 . The transgenic yeast strain of  claim 38 , wherein the araA gene is derived from  E. coli  or  B. subtilis.    
     
     
         40 . The transgenic yeast strain of  claim 38 , wherein the transgenic yeast strain has a deletion or disruption of the aldose reductase gene. 
     
     
         41 . The transgenic yeast strain of  claim 40 , wherein the transgenic yeast strain has a deletion or disruption of the open reading frame (ORF) yhr104w. 
     
     
         42 . The transgenic yeast strain of  claim 38 , wherein the transgenic yeast strain is capable of producing at least 4.7 g/liter of ethanol from 19 g/L of arabinose. 
     
     
         43 . The transgenic yeast strain of  claim 38 , wherein the transgenic yeast strain has a mutation of the aldose reductase gene. 
     
     
         44 . The transgenic yeast strain of  claim 38 , wherein the yeast strain includes at least one arabinose transporter gene selected from the group consisting of GAL2, KmLAT1 and PgLAT2. 
     
     
         45 . An ethanol producing yeast strain, comprising at least one heterologous arabinose transporter wherein the ethanol producing yeast strain is aldose reductase (AR) deficient (AR-). 
     
     
         46 . The ethanol producing yeast strain of  claim 45 , further comprising at least two heterologous arabinose transporters. 
     
     
         47 . The ethanol producing yeast strain of  claim 45 , wherein the heterologous arabinose transporter is from a non-conventional yeast species. 
     
     
         48 . The ethanol producing yeast strain of  claim 47 , wherein the heterologous arabinose transporter is KmLat1 or PgLat2. 
     
     
         49 . The ethanol producing yeast strain of  claim 45 , wherein the yeast strain overexpresses a GAL2-encoded galactose permease. 
     
     
         50 . The ethanol producing yeast strain of  claim 49 , wherein the yeast derived GAL2-encoded galactose permease is under control of a TDH3 promoter. 
     
     
         51 . The ethanol producing yeast strain of  claim 45 , further comprising one or more bacterial genes that facilitate arabinose utilization and fermentation in the ethanol producing yeast strain. 
     
     
         52 . The ethanol producing yeast strain of  claim 51 , wherein the one or more bacterial genes for facilitated arabinose utilization and fermentation are selected from the group consisting of araA, araB and araD. 
     
     
         53 . The ethanol producing yeast strain of  claim 51 , comprising araA, araB and araD. 
     
     
         54 . The ethanol producing yeast strain of  claim 52 , wherein at least one of araA, araB and araD is derived from  E. coli.    
     
     
         55 . A method for producing ethanol utilizing a transgenic yeast strain, comprising the steps of:
 providing a material comprising arabinose,   performing a fermentation of the material using the transgenic yeast strain, wherein the transgenic yeast strain comprises genes for the expression of an araA peptide, an araB peptide and an araD peptide and wherein the transgenic yeast strain is aldose reductase deficient (AR − ); and   producing at least 8 g/liter ethanol.   
     
     
         56 . The method of  claim 55 , wherein the material comprises arabinose and glucose, and the method produces at least 17 g/liter ethanol. 
     
     
         57 . The method of  claim 55 , wherein the transgenic yeast strain has a deletion or disruption of the aldose reductase gene.