468 ENZYMES OF YEAST. 



p. 246, vol. ii.). Nitrous acid has a greater restrictive influence 

 on cell- juice fermentation than any of its salts. E. BUCHNER (X.) 

 found that acetic acid, tartaric acid, and especially lactic acid, had 

 a less injurious effect, the initial diminution in the liberation of 

 carbon dioxide disappearing when the experiment was prolonged 

 for some time. In the case of added lactic acid (0.3 per cent.), 

 the fermentative power was even higher than in the check 

 experiments. 



With regard to the influence of other salts on yeast juice 

 fermentation (see p. 245, vol. ii.), E. BUCHNER and RAPP (III. and 

 VIII.) ascertained, by means of quantitative experiments, that 

 i per cent, solutions of sodium chloride and ammonium chloride 

 retarded the fermentative power to only a small extent, whereas 

 corresponding solutions of the sulphates of soda, ammonia and 

 magnesia had a more serious effect, and calcium chloride was 

 highly injurious, whereas barium chloride of equal strength was 

 innocuous, and in fact rather favourable. According to BUCHNER 

 and ANTONI (II.), manganese sulphate, aluminium sulphate, 

 ferrous sulphate and cobalt sulphate are either inoperative or 

 only adverse in their effect. Turning to organic substances, urea 

 and glycocoll increase the fermentative power, but, on the other 

 hand, antipeptone, hemi-albuminose and protalbuminose are 

 directly injurious. The phosphates, and especially the secon- 

 dary phosphates, are particularly beneficial in yeast- juice fer- 

 mentation, an addition of 14 per cent, having good results. 

 WROBLEWSKI (V.) finds that the optimum dose of secondary 

 phosphates is 1.25 per cent. The beneficial effect of these salts 

 is increased by the presence of acids and alkalis ; and WROB- 

 LEWSKI (V.) credits these salts with protective properties, 

 exercised by neutralising the added acids and alkalis, so that the 

 phosphates guard the living cell from the attacks of acids and 

 bases. Additional matter on this point is furnished by the newer 

 researches of HARDEN and YOUNG (II.), according to whom the 

 alkali phosphate added to the yeast juice is no longer precipitable 

 by magnesia mixture after the fermentation is ended a behaviour 

 indicating the formation of an organic compound of phosphoric 

 acid in the juice. From experiments made by BUCHNER and 

 ANTONI (II.), it appears that the addition of lecithin has con- 

 siderable influence on zymase fermentation ; and these authorities 

 state that the active principle may consist of organic compounds 

 of phosphoric acid. 



BUCHNER and RAPP (VIII.) report that an extensive liberation 

 of nitrogen follows the addition of nitrites to expressed yeast 

 juice. The process is a purely chemical one and originates in the 

 action of the amino acids and other amino compounds of the 

 juice on the nitrites. The same observation was reported by 

 WROBLEWSKI (IV.), who also found that an addition of 0.25 per cent, 

 of sodium nitrite increased the fermentative activity of yeast juice. 



