Lewis Knudson 183 



8. The economical methods are (a) those in which growth occurs 

 under aerobic conditions and the tannic acid is supplemented by 

 cane sugar; or (b) those in which, with tannic acid alone, the sup- 

 ply of oxygen is limited to a small amount. 



9. The presence of 10 per cent cane sugar does not inhibit the 

 secretion of the enzyme tannase by Aspergillus niger, but it does 

 seem to inhibit to some extent the secretion of the tannase by Peni- 

 cillium sp. 



10. The enzyme is secreted into the culture solution by sub- 

 mersed mycelium as well as by surface growth. There is no evi- 

 dence that tannic acid is used directly; but the evidence seems to 

 indicate that tannic acid is first transformed into gallic acid and the 

 gallic acid then utilized. 



APPENDIX. 



Investigators previously occupied with tannic acid fermentation usually 

 employed Aspergillus niger together with a species of Penicillium whigh they 

 have designated Penicillium glaucum. As has been pointed out by Thorn" 

 the name Penicillium glaucum has in the past been applied to so many differ- 

 ent species that the only idea conveyed by its use is a general concept of the 

 genus. VanTieghem" applied the name to denote the species of Penicillium 

 which he isolated from gall nuts, and it is probable that other students of 

 tannic acid fermentation used the same organism. 



In the work of the writer a trial of a number of organisms was made and 

 the Penicillium employed was secured from a culture labeled Penicillium 

 blivaceum. That identification was incorrect, and then it was believed that 

 the organism might be the one which develops on the gall nuts, bat this also 

 proved erroneous, as is indicated subsequently. 



In attempting to determine the Penicillium sp. used in these experiments 

 it was found that the organism did not correspond to any of the species des- 

 cribed by Thom.'* Instead, however, of withholding publication of these 

 investigations until the organism should be definitely determined, it was 

 thought best to present here a brief description and certain cultural charac- 

 teristics of the organism. It is, furthermore, the intention of the writer to 

 make a study of the relation of the various species of Penicillium to tannic 

 acid fermentation, and it is hoped by that time to have determined definitely 

 the two species of Penicillium which are now known to develop in a 10 per 

 cent solution of tannic acid. 



The Penicillium sp. used in these experiments possesses only a single 

 whorl of unbranched conidia-bearing cells (sterigmata), and might therefore 



*2 Charles Thorn: Cultural Studies of Penicillium,Bureau of Animal 

 Industry, Bulletin 118, pp. 107, 1910. 

 " Log. cit. 

 ** Loc. cit. 



