84 FERMENTATION BY MUCOES. 



alcohol ; and we will divide these into sugars on the one hand 

 and starch and dextrin on the other, so as to be able to classify 

 the species of this genus on the basis of their practical applica- 

 bility. Starch and dextrin do not yield alcohol direct, but only 

 after they have been converted into sugar ; consequently they 

 can only come into consideration in the case of such Mticors as 

 are capable of producing saccharifying enzymes. These species 

 will be fully described in the next chapter, and for the present 

 we will deal solely with the formation of alcohol from sugars, 

 and with the inversion of the latter. So far as is known, 

 saccharose is split up by only two of the species hitherto men- 

 tioned. One of these — according to Fitz (IX. and XL), Bre- 

 FELD (XV.), and Haxsek (VIII.) — is Muror racemosus ; the 

 other was observed by the last-named worker, and is probably 

 nothing more than a sport of the same organism. These two 

 species produce an inverting enzyme, which faculty constitutes 

 a sharply defined distinction between them and the Mucor and 

 Rhizopus species hitherto known. Hansen's comparative ex- 

 periments revealed the importance of this physiological charac- 

 teristic as a means of differentiating the individual species ; and 

 its value for the purpose in view is so much the greater from 

 the fact that its occurrence in these two species, and absence 

 in all the rest, is quite independent of the envii'oument ; which 

 is more than can be said of morphological characteristics. It is 

 therefore advisable to point out at once that saccharose cannot 

 be inverted or fermented by Mucor viucedo, M. erectus, M. spi?i- 

 osus, M. alternans, M. circinelloides, M. Mouxii, or Rhhopus^ 

 nigrica7is, though they can draw upon it as a source of carbon. 

 On the other hand, with the exception of Rhizopus nigricaTiSy 

 they can all attack maltose and convert it into alcohol. Whether 

 the fermentation is preceded by a fission of this disaccharide 

 into hexoses, as occurs in fermentation with true yeasts, has not 

 yet been investigated. None of them is capable of convei-ting 

 galactose into alcohol direct, though they can do so after inver- 

 sion, as shown by Fitz (XI.) in the case of Mucor racemosug. 

 This latter is therefore equally incapable with the other six 

 species of pi'oducing an enzyme that can hydrolyse milk sugar. 

 According to Dubourg (I.), trehalose can be fermented to 

 alcohol by Mucor alternant, though raflOnose cannot. From 

 dextrose and Isevulose each of the above-mentioned Mucorece 

 can produce alcohol by intramolecidar respiration ; and the same- 

 naturally also applies to the invert sugar formed from sac- 

 charose, by chemical reagents or the preparatory activity of 

 other organisms. Presuming the above-mentioned preliminary 

 hydrolysis of maltose to be correct, the formation of alcohol by 

 the intramolecular respiration of Alucorece will fall under the 

 same law as has already been found to prevail, without excep- 

 tion, in the alcoholic fermentation excited by Swrliaromycetea 



