Methods for improving malic acid production in filamentous fungi

Abstract

The present invention relates to methods of producing a C4 dicarboxylic acid, comprising: (a) cultivating a filamentous fungal host cell comprising a polynucleotide selected from the group consisting of a heterologous first polynucleotide encoding a C4 dicarboxylic acid transporter, a heterologous second polynucleotide encoding a malate dehydrogenase, and a heterologous third polynucleotide encoding a pyruvate carboxylase; wherein the filamentous fungal host cell is capable of secreting increased levels of the C4 dicarboxylic acid compared to the filamentous fungal host cell without the heterologous polynucleotide when cultivated under the same conditions; and (b) recovering the C4 dicarboxylic acid. The present invention also relates to methods for increasing C4 dicarboxylic acid production, filamentous fungal host cells and malate dehydrogenase variants.

What is claimed is: 
     
         1 . An  Aspergillus oryzae  host cell comprising a heterologous polynucleotide encoding a malic acid transporter, wherein the malic acid transporter is selected from:
 (a) a malic acid transporter comprising an amino acid sequence having at least 95% sequence identity with SEQ ID NO: 36;   (b) a malic acid transporter encoded by a polynucleotide that hybridizes under very high stringency conditions with the full-length complementary strand to SEQ ID NO: 35 or SEQ ID NO: 37; and   (c) a malic acid transporter encoded by a polynucleotide comprising a nucleotide sequence having at least 95% sequence identity with SEQ ID NO: 35 or SEQ ID NO: 37;   and wherein the host cell is capable of secreting increased levels of malic acid compared to the host cell without the heterologous polynucleotide encoding the malic acid transporter when cultivated under the same conditions.   
     
     
         2 . The host cell of  claim 1 , wherein the malic acid transporter comprises an amino acid sequence having at least 95% sequence identity sequence identity with SEQ ID NO: 36. 
     
     
         3 . The host cell of  claim 1 , wherein the malic acid transporter comprises an amino acid sequence having at least 97% sequence identity with SEQ ID NO: 36. 
     
     
         4 . The host cell of  claim 1 , wherein the malic acid transporter comprises an amino acid sequence having at least 98% sequence identity with SEQ ID NO: 36. 
     
     
         5 . The host cell of  claim 1 , wherein the malic acid transporter comprises an amino acid sequence having at least 99% sequence identity with SEQ ID NO: 36. 
     
     
         6 . The host cell of  claim 1 , wherein the malic acid transporter is encoded by a polynucleotide that hybridizes under very high stringency conditions with the full-length complementary strand to SEQ ID NO: 35 or SEQ ID NO: 37. 
     
     
         7 . The host cell of  claim 1 , wherein the malic acid transporter is encoded by a polynucleotide comprising a nucleotide sequence having at least 95% sequence identity with SEQ ID NO: 35 or SEQ ID NO: 37. 
     
     
         8 . The host cell of  claim 1 , wherein the malic acid transporter comprises or consists of SEQ ID NO: 36. 
     
     
         9 . The host cell of  claim 1 , wherein the heterologous polynucleotide encoding the malic acid transporter is operably linked to a promoter foreign to the polynucleotide encoding the malic acid transporter. 
     
     
         10 . The host cell of  claim 1 , further comprising a heterologous polynucleotide encoding a malate dehydrogenase. 
     
     
         11 . The host cell of  claim 10 , wherein the malate dehydrogenase comprises or consists of SEQ ID NO: 18 or SEQ ID NO: 20. 
     
     
         12 . The host cell of  claim 1 , further comprising a heterologous polynucleotide encoding a pyruvate carboxylase. 
     
     
         13 . The host cell of  claim 12 , wherein the pyruvate carboxylase comprises or consists of SEQ ID NO: 27. 
     
     
         14 . The host cell of  claim 1 , wherein host cell is capable of secreting at least 50% more malic acid compared to the filamentous fungal host cell without the polynucleotide encoding the malic acid transporter when cultivated under the same conditions. 
     
     
         15 . The host cell of  claim 1 , wherein the host cell is capable of producing malic acid at a level greater than 120 g/L. 
     
     
         16 . A method of producing malic acid, comprising:
 (a) cultivating the host cell of  claim 1  in a medium; and   (b) recovering the malic acid.   
     
     
         17 . An  Aspergillus oryzae  host cell comprising a heterologous polynucleotide encoding a malic acid transporter, wherein the malic acid transporter differs by no more than ten amino acids from SEQ ID NO: 36;
 and wherein the host cell is capable of secreting more malic acid compared to the host cell without the heterologous polynucleotide encoding the malic acid transporter when cultivated under the same conditions.   
     
     
         18 . The host cell of  claim 17 , wherein the malic acid transporter differs by conservative substitution(s) of SEQ ID NO: 36. 
     
     
         19 . The host cell of  claim 17 , wherein the malic acid transporter differs by no more than five amino acids from SEQ ID NO: 36. 
     
     
         20 . The host cell of  claim 19 , wherein the malic acid transporter differs by conservative substitution(s) of SEQ ID NO: 36. 
     
     
         21 . The host cell of  claim 17 , wherein the cell is capable of secreting at least 50% more malic acid compared to the host cell without the heterologous polynucleotide encoding the malic acid transporter when cultivated under the same conditions. 
     
     
         22 . A method of producing malic acid, comprising:
 (a) cultivating the host cell of  claim 20  in a medium; and   (b) recovering the malic acid.