i8o 



Tannic Acid Fermentation 



offered as the only source of carbon, the yield of gallic acid is 

 obviously dependent upon the amount of growth. Van Tieg- 

 hem*" found that 0.022 gram's weight of mycelium transformed 

 48.3 grams of tannic acid in ten days at 35°. The growth is 

 greatly diminished by the absence of oxygen, consequently the 

 oxygen supply is a factor influencing the yield of galUc acid. In 

 order to compare the yield under aerobic and anaerobic conditions, 

 another experiment was performed. Solution B was used, to 

 which was added tannic acid. Into each of six Erlenmeyers of 

 150 cc. capacity were placed 50 cc. of the solution. Four of the 

 flasks were plugged with cotton, while the other two were fitted 

 with perforated rubber stoppers. After steriUzation the perfora- 

 tions were plugged with pieces of glass rod and these, together with 

 two of the flasks plugged with cotton, were inoculated with Asper- 

 gillus niger. The flasks fitted with the rubber stoppers contained 

 approximately 100 cc. of air and therefore about 20 cc. of oxygen. 

 The cultures were incubated at 31° and at the end of twenty-eight 

 days and forty days analyses were made. The results follow in 

 table X. 



TABLE X. 



It is at once evident that the inhibition of growth due to defi- 

 ciency of oxygen is favorable to a good yield of gaUic acid. No 

 doubt if the culture in limited oxygen supply had been analyzed 

 sooner a greater yield of gallic acid could have been obtained. 

 With respect to the condition in aerobic cultures it may be stated 

 that cultures, identical with those above, showed on the fourth day 

 a gain of 0.484 gram of gallic acid, though only half of the tannic 

 acid had been transformed, and the weight of the mycelium pro- 

 duced was 0.0314 gram. 



Comparison of methods. In order to determine more definitely 

 the yield of the gallic acid under conditions in which the supply of 



*' Loc. cit. 



