The formation of pyruvic and dimethylpyruvic acids by Aspergillus niger

Summary o 1. The formation both of pyruvic and dimethylpyruvic acids from glycerol by preformed felts of the mold Aspergillus niger, when placed on a glycerol solution containing NH 4Cl, KH 2PO 4, and Na 2SO 3, is considerably enhanced when ethylene glycol is added to the medium, and is also enhanced, though to a less extent, by addition of glycolic acid. In neither case, however, is the increase of yield as great as are the increases produced by addition of sodium acetate to the culture fluid. 2. In similar conditions, the addition of ethanol depresses the formation of pyruvic acid but has not much effect upon that of dimethyl-pyruvic acid. 3. Addition of sodium pyruvate to the glycerol medium reduces the formation of dimethylpyruvic acid to an insignificant quantity, while sodium propionate prevents entirely the formation of both pyruvic and dimethylpyruvic acids. 4. Aspergillus niger forms pyruvic and dimethylpyruvic acids in very small yields from erythritol in Hida's medium, and addition of acetate increases somewhat the yield of both acids. 5. Formation of both keto acids from glucose in Hida's medium is not influenced by addition thereto either of sodium fluoride (0.003 M) or of sodium iodoacetate (0.002 M). Addition of sodium cyanide (0.02 M) to this glucose medium reduces the yield of pyruvic acid to a trace and that of dimethylpyruvic acid to less than one-quarter of the normal yield. 6. Suggestions are made concerning the manner in which pyruvic acid and dimethylpyruvic acid may have been formed under the experimental conditions cited in this communication.