ON THE HYDROLYSIS OF SUGARS. 269 



B 2. — Inversion by Enzymeg. 



Certain organisms which develop very readily in cane sugar solutions 

 are found to invert the sugar. Such for example are Aspergillus niger, 

 Penicilhim glaucum and most yeasts. 



It was first noticed by Dubrunfaut that under the influence of yeasts 

 sugar is converted into suci'e incrystallisahle and Persoz showed that the 

 change is accompanied by optical inversion. Pasteur supposed that the 

 yeast produced succinic acid, which then inverted the sugar in virtue of 

 1860 ^*^ acidity. Berthelot, however, showed^ that succinic acid is 

 not sufficiently active to bring about inversion so quickly as it is 

 accomplished- by yeast; moreover, yeast can invert sugar even in an 

 alkaline solution. He succeeded in e-^tracting the nitrogenous active 

 principle of the yeast by water. 



This enzyme, ' invertase ' or ' sucrase,' which is capable of inverting 

 cane sugar is not present in all yeasts. For instance, Saccharomyces 

 octosporus, which is capable of hydrolysing and fermenting maltose, has 

 no action on cane sugar.^ In fact, there is an enzyme specially adapted 

 to hydrolyse every biose and no other sugar. 



A useful summary of this subject is given by Euler.^ 



B -3. — Inversion hy Acids. 



Whereas each biose sugar requires a special enzyme to hydrolyse it, 

 the catalytic action of acids is a general property, all acids hydro- 

 lysing all bioses. The rate of the action, however, varies enormouslv 

 with the nature of the acid and of the sugar [vide Sections D and M). 



The hydrolysis of cane sugar is most readily eflected by sulphuric acid ; 

 a gramme molecular solution of this acid has an activity 7 "4 per cent, more 

 powerful than that of a molecular solution of hydrochloric acid, and is 

 270 times as powerful as acetic acid. 



1880 Even carbonic acid, as Lippmann has shown, can bring about the 



inversion of cane sugar, this action being the more rapid if the 

 solution be heated under pressure (see also Mauraene, 1881, and Pfyl and 

 Linne, 1905). 



B 4. — Inversion by Acid Salts. 



The ' acid salts ' of dibasic acids are also able to bring about 



jggg inversion. This was remarked upon by Spohr with reference to 

 the acid sulphates. 



1892 Trevor used the sugar-inversion method to estimate the 'degree 



of ionisation,' i.e. the acidity of various acid salts, such as sodium 



1894 Jiydrogen succinate. Noyes also applied Trevor's method to deter- 

 mine the degree of ionisation of potassium bitartrate at 100° C. 



1 903 Magnanini-Modena has applied the inversion of cane sugar as a 



test for KHSO4 ill wine which has been treated with gypsum. 



' Comptes Rendui, 50, p. 980. 



^ Gayon (1881) has since shown that the action of succinic acid is inhibited by 

 yeast. 



^ Vide E. F. Armstrong (1905), Proc. Roy. Soc.,'B 76, p. 603. 



* ZeiU. Physiol. Chem., 1905, 45, p. 420. Comp. The SolnUe Ferments by Reynolds 

 Green. 



