Figure 3.

Metabolic engineering of butyrate-producing yeast.

(a) Biosynthetic pathway for producing butyrate. (b) The butyrate titer of the recombinant strains with acetoacetyl-CoA enhancement module. ERG10 and MCT1 are responsible for the synthesis of acetoacetyl-CoA. The purple column represents the strain with the highest yield. (c) The butyrate titer of the recombinant strains with acetyl-CoA enhancement module. MLS1 and CIT2 are responsible for the glyoxylate cycle and knockout of these two genes contributing to the accumulation of acetyl-CoA in the cytoplasm. ACS1 and ACS2 are responsible for the aerobic and anaerobic synthesis of acetyl-CoA, respectively. ACH1 is responsible for CoASH transfer from succinyl-CoA to acetate. ALD6 is required for the conversion of acetaldehyde to acetate. The blue column represents the strain with the highest yield. (d) The butyrate titer of the recombinant strains with NADH enhancement module. ADH1 and ADH4 participate in the synthesis of ethanol by consuming NADH. GPD1 and GPD2 are responsible for glycerol synthesis by consuming NADH. The red column represents the strain with the highest yield. (e) The butyrate production of the recombinant strains with acyl-CoA regulation module. FAA1 and FAA4 are responsible for the synthesis of long-chain fatty acids. FAT1 is involved in the synthesis of very long-chain fatty acids and the transport of fatty acids. The orange column represents the strain with the highest yield.