462 ENZYMES OF YEAST. 



L. GERET (I.) with chloroform, DORMEYER (I.) with ether and 

 chloroform, and J. DE REY-PAILHADE (V.) with 22 per cent, 

 alcohol. In order to recover a yeast preparation similar to meat 

 extract, E. DE MEULEMEESTER (I.) proposed to treat yeast with 

 gum arabic; H. VAN LAER (IX.) used 2 per cent, of common salt, 

 and H. BUCHNER and M. GRUBER (I.) used ether. Yeast extracts 

 of this kind are met with in commerce under various names : 

 siris, wuck, ovos, &c. (seep. 168, vol. ii.). 



318. General Properties of Expressed Yeast Juice. 



The expressed yeast juice prepared by the method of Buchner 

 and Hahn is a clear, though opalescent, liquid of a yellow to 

 brownish yellow colour, and with a strong smell and taste of yeast. 

 When freshly prepared, it has a faintly acid reaction, though 

 AHRENS (I.) states that that prepared by him is slightly alkaline, 

 but quickly turns acid. The fresh juice prepared by WROBLEW- 

 SKI (III.) was also faintly alkaline. 



According to this worker (IV.), the juice is optically inactive, 

 which is rather surprising in view of the protein content. 

 E. BUCHNER'S (X.) investigations on this point have not yet led 

 to any decisive results. 



When the yeast juice is treated with strong alkali, mineral 

 acids or acetic acid, a voluminous precipitate is formed. On 

 being warmed, coagulation of protein occurs at 35-4o C. , 

 becoming much stronger at higher temperatures, so that the 

 whole mass seemed curdled. This is probably the first time that 

 a preparation so rich in protein has been obtained from the cells 

 of budding fungi. By means of partial coagulation, WROBLEWSKI 

 (III.) was able to differentiate several coagulable proteids. He 

 points out that the temperature of coagulation (41 C.) of the one 

 proteid coincides with that at which the fermentative action of 

 the juice ceases; and that furthermore the proteid coagulating 

 at 41 C. appears to be digested before any of the others. 



According to E. BUCHNER (X.), the chemical analysis of 

 different samples of juice gave the following results : sp. gr. 

 1.027-1.057 ; content of dry matter 8.5-14.5 per cent., coagulable 

 protein 5-6 per cent., total nitrogen 0.82-1.45 per cent., organic 

 phosphorus about 0.228 per cent., organic sulphur about 0.065 P er 

 cent., ash 1.3-1.8 per cent, (seealsop. 192, vol. ii.). The ash con- 

 stituents are : potassium, sodium calcium, magnesium, phosphoric 

 acid, sulphuric acid, chlorine and silica (the latter from the 

 kieselguhr). AHRENS (I.) found in the ash-free substance, 45.4 

 per cent, of carbon, 7.5 per cent, of hydrogen and 10.64 P er cen t- 

 of nitrogen (see also p. 204, vol. ii.). WROBLEWSKI (I. and III.) has 

 also identified the following substances in expressed yeast juice : 

 albumens, globulins, mucinous substances, proteoses, peptones, 

 nucleoalbumens, compound carbohydrates and a special crystalline 



