i6o Tannic Acid Fermentation 



well as the tannin of sumach and chestnut. The pathological 

 tannins are hydrolyzed by boiling with acids or through the action 

 of the enz3Tne tannase, gallic acid resulting. For other distin- 

 guishing characteristics of the tannins Trimble's^ and Proctor's' 

 treatises may be consulted, and for a discussion of the diverse 

 views held regarding their chemistry reference should be made to 

 special papers on the subject. 



This paper is concerned with the fermentation of the tannin 

 from oak galls, which is frequently termed gailotannic acid. 



History of tannic add fermentation. Scheele* found in 1786 that gallic 

 acid was present in the gall nuts. Robiquet* attributed the fermentation 

 of the gall nuts to a ferment within the gall nut. Laroque' considered the 

 formation of gallic acid from tannic acid to be due either to a ferment or to 

 oxidation. He further found that various toxic substances could inhibit 

 the fermentation. Ed. Robiquet' showed that the tannic acid was trans- 

 formed during the fermentation and he believed the transformation to be 

 due to the ferment pectase which he extracted from the gall nuts. Witt- 

 stein' stated that beer yeast aided tannin fermentation by fermenting the 

 sugars and other products present. Van Tieghem' was the first, however, 

 to demonstrate that the formation of gallic acid during fermentation is due 

 to the action of fungus organisms, and not to enzymes pre-existing in the 

 galls, nor to oxidation by the air. He stated further that the organisms 

 were Penicillium glaucum and a new organism which he named Aspergillus 

 niger. He found that if the growth was submersed, the tannic acid was con- 

 verted into gallic acid and glucose, the glucose being gradually used up, the 

 gallic acid remaining. He stated further that if the growth was on the sur- 

 face, sporulation and greater growth occurred and that the tannic acid was 

 destroyed directly, the slight hydrolysis being due to submerged mycelium, 

 the resulting glucose and gallic acid being then assimilated. 



^ H. Trimble : The Tannins, Part I, 168 pp. ; Part II, 172 pp., 1892. 



' H. K. Proctor: Leather Industry. Laboratory Book, 2nd edition, 450 pp 

 1908. 



' Quoted from H. Trimble: loc. cit. 



5M. Robiquet: Faits pour servir k de I'acide gallique, Ann. de chim. 

 et de phys., 2" serie, Ixiv, pp. 385-409, 1837. 



« A. Laroque: Neue Untersuchungen uber Gallussaure, Ann. d. Chem. u. 

 Pharm., xxxix, pp. 37-100, 1841. 



' Ed. Robiquet: Recherches sur la fermentation gallique, Ann. de chim. 

 et de phys., 3° serie, xxxix, pp. 453-460, 1853. 



'Wittstein: Jahresber. Uber die Fortschritte der Chemie, 1853, p. 435. 



' Ph. VanTieghem: Sur la fermentation gallique, Compt. rend, de I'Acad 

 des Sci., Ixv, pp. 1091-95, 1867. 



