INVERTASE. 517 



culture yeasts used in brewing, distillery work and pressed yeast 

 making, and therefore in all top- and bottom -fermentation yeasts 

 of the Sacch. cerevisice type, both of the Frohberg and Saaz races 

 comprised in the types OF, OS, UF, and US (see p. 540, vol. ii.). 

 All the true wine yeasts also contain invertase; but, on the 

 other hand, it is absent from Schizos. octosporus (see pp. 274- 

 281, vol. ii.). Invertase is, however, present in a number of other 

 budding fungi, though not in any of the examined races of Sacch. 

 apiculatus (see p. 431, vol. ii.) and most Torulacece (see p. 398, 

 vol. ii.). Of the latter, however, HARTMANN'S (I.) Torula collicu- 

 losa ferments saccharose without difficulty, whereas other species 

 are incapable of decomposing this sugar. In this connection, 

 further investigation is urgently required, since, in most of the 

 work already done, attention was mainly directed to ascertaining 

 whether the organisms employed were able to ferment saccharose, 

 and not to determining the presence of invertase. 



In the preparation of invei tase in the purest, i.e., most active, 

 condition possible, it is the almost universal practice to employ 

 Sacch. cerevisice, of either top- or bottom-fermentation type. In 

 the older methods the first stage was to kill the yeast by means of 

 alcohol or ether, in order to extract the invertase afterwards with 

 water or glycerine compare BERTHELOT (III.), LIEBIG (III.), 

 HOPPE-SEYLER (IX.), GUNNING (I.), and DONATH (III.). The 

 resulting solution is precipitated, fractionally, with strong or 

 absolute alcohol, under which treatment the earlier fractions have 

 less enzymatic power than the later ones. The precipitates are 

 washed with absolute alcohol, and dried in the desiccator. In 

 other methods, according to BARTH (II.) and AUTHOR (V.), the 

 yeast is first carefully warmed, to expel the bulk of its moisture, 

 and is then dried more energetically, and the resulting powder 

 is extracted. An exceedingly powerful solution of invertase is 

 obtained by allowing yeast to ferment spontaneously O'SULLIVAN 

 and TOMPSON (I.) or by recovering the expressed juice by the 

 Buclmer method. According to ISSAEW (I.), plasmolysing pressed 

 yeast with saccharose will furnish a very active invertase, from 

 which the dissolved saccharose can be eliminated by fermentation . 

 The relatively purest invertase, however, is obtained by killing 

 the yeast and extracting it with glycerine or water, whether the 

 killing be effected by treatment with alcohol or ether, or, pre- 

 ferably, by heating the carefully dried yeast to 100 C. and over. 

 According to OSBORNE (I.), the yeast, after being killed with 

 alcohol, should be digested with chloroform water at a moderate 

 heat for some time, the nitrate being poured out into 96 per cent, 

 alcohol. The deposited flakes are washed with alcohol, dried, and 

 dissolved in 25 parts of water, the earthy phosphates still present 

 being thrown down by a careful addition of ammonia, and the 

 filtrate dialysed and then evaporated in vacuo. WROBLEWSKI (IV.) 

 also employed dialysis for purifying the enzyme ; but this worker 



