Formation of pyruvic acid from malic acid 



by microbes. 



By Prof. M. W. BEIJERINCK and Dr. T. FOLPMERS. 



Proceedings of the Section of Sciences, Kon. Akademie van Wetenschappen, Amster- 

 dam, Vol. XVIII, 1916, p. 11981200. Verscheen onder den titel Vorming van 

 brandigdruivenzuur uit appelzuur door bakterien in Verslagen Kon. Akademie van 

 Wetenschappen, Wis-en Natuurk. Afd., Amsterdam, Deel XXIV, 1916, biz. 11161119. 



Of the organic acids malic acid seems the most easily decomposed by microbes. 

 Then chime might follow in the readiness of this decomposition, whereas 

 the other acids are more difficult to split up. 



The decomposition can take place by fermentation at exclusion of air, or by 

 oxydation. Here oxidation will only be discussed. 



As to the malates their oxidation is commonly a complete conversion into water, 

 carbonate, and carbonic acid; it can be caused by a number of microbes. But among 

 the bacteria numerous species occur which at the same time produce a less complete 

 oxidation of the malates, whereby especially pyruvic acid is of importance. 



The reaction evidently is: 



C 4 H 6 O 5 + O = C 3 H 4 O 3 + CO 2 + H 2 O 

 Malic acid Pyruvic acid 



or, as to calciummalate: 



+ O 2 = C 6 H 6 CaO 6 + CaCO 3 + CO 2 + H 2 O. 



With potassiummalate the reaction has the same course. As a reagent on the 

 pyruvic acid a ferric salt is used, such as ferric chlorid or ferric citrate, giving an 

 intensive and characteristic orange yellow colour, which by the action of dilute 

 hydrochloric acid first passes into red, then disappears. 



The following experiment is simple and convincing. 



Ordinary agar is diluted with once or twice its volume of pure 2% agar dis- 

 solved in water; to this mixture is added i or 2% calciummalate, which does not 

 quite dissolve, and a little ferric citrate or ferric chlorid as an indicator. 



After pouring out and solidification a plate is obtained, still turbid by the not quite 

 dissolved malate. 



Canal water is now flowed over the plate and the excess removed so that isolated 

 colonies can develop; or on the surface of the plate streaks of various species of 

 bacteria are made and the plate is then kept at 25 to 30 C. After a few days 

 around most of the colonies or streaks the said reaction appears with great distinct- 



