xji.a. 6 Brill and Thurlow: Alcohol from Molasses 273 



most suitable for them and should result in an accompanying 

 benefit to the distiller in the increased yields of alcohol. 



In our search for a suitable yeast we were assisted by Mr. 

 K. B. Graae, bacteriologist, Bureau of Science, who isolated 

 five cultures of yeast from fermenting nipa juice. These after- 

 ward proved to belong to the same race of top-fermenting yeast, 

 a Saccharomyces. The cells are smaller than those of race II 

 or race XII 13 and are fairly quick-fermenting. The use of a 

 quick-fermenting yeast is an advantage, since owing to its rapid 

 growth it crowds out bacteria and wild yeasts. 



For the growth of yeast, properly adjusted foodstuffs are 

 necessary. A solution of pure cane sugar would undergo 

 fermentation, but the yeast would not grow and the fer- 

 mentation would stop after the enzymes already formulated by 

 the yeast became exhausted. Yeasts require for their growth 

 certain organic and inorganic compounds, such as nitrogen 

 bodies (ammonium salts, amides, peptones, phosphates, sulphates, 

 potassium, and magnesium salts), which are always present in 

 available form in sufficient quantities in grape juice and beer 

 wort, but not in molasses. The presence of proper food 

 stimulates yeast growth, and rapid growth of cultured yeast 

 prevents the development of bacteria and wild yeast. The 

 latter are undesirable, since some of them convert the sugar 

 into substances other than alcohol and thus lessen the yield, 

 while others produce alcohol, but in reduced amounts. Yeast 

 can be accustomed to the presence of the' antiseptics, so that 

 they withstand them when present in not too large quantities. 14 

 Advantage is taken of this fact to keep the ferment free from 

 bacteria and wild yeast, which are much more susceptible to 

 the influence of such reagents.^ Sulphuric acid and salts of 

 hydrofluoric acid are extensively used for this purpose. 



A 5 per cent solution of alcohol is strong enough to stop the 

 propagation of many yeasts, but the enzymes continue to act for 

 some time after the propagation of the yeast has stopped. 

 Others by cultivation have become accustomed to more concen- 

 trated solutions ; consequently they will ferment in much stronger 

 solutions. A concentrated solution of molasses ferments more 

 slowly after a certain period, because of this higher percentage 



13 Race II and race XII are two famous yeasts developed in Germany 

 and used largely in continental Europe because of their ability to ferment 

 concentrated solutions quickly. 



14 Among the antiseptics are mercuric chloride, copper sulphate, sul- 

 phurous acid, hydrofluoric acid, nitric acid, nitrous acid, salicylic acid, 

 formaldehyde, carbon disulphide, chloroform, ether, alcohol, etc. 



