CHAPTEE IV 



BACTERIA AND FERMENTATION 



Early Work — Kinds of Fermentation : (1) Alcoholic Fermentation, Ascospores, 

 Pure Cultures, Films ; (2) Acetous Fermentation ; (3) Lactic Acid Fermenta- 

 tion ; (4) Butyric Fermentation ; (5) Ammoniacal Fermentation — Diseases of 

 Wine and Beer: Turbidity, Ropiness, Bitterness, etc. — Industrial Applica- 

 tions of Bacterial Ferments. 



It was Pasteur who, in 1857, first propounded the true cause and 

 process of fermentation. The breaking down of sugar into alcohol 

 and carbonic acid gas had been known, of course, for a long period. 

 Since the time of Spallanzani (1776) the putrefactive changes in 

 liquids and organic matter had been prevented by boiling and subse- 

 quently sealing the flask or vessel containing the fluid. Moreover, 

 this successful preventive practice had been in some measure 

 correctly interpreted as due to the exclusion of the atmosphere, but 

 wrongly credited to the exclusion of the oxygen of the air. It was 

 not until the beginning of the present century that authorities modi- 

 fied their view and declared in favour of yeast cells as the agents in 

 the production of fermentation. That this process was due to 

 oxygen per se was disproved by Schwann, who showed that so long 

 as the oxygen admitted to the flask of fermentable fluid was sterilised 

 no fermentation occurred. It was thus obvious that it was not the 

 atmosphere or the oxygen of the atmosphere, but some fermenting 

 agent borne into the flask by the admission of unsterilised air. It 

 was but a step further to establish this hypothesis by adding 

 unsterilised air plus some antiseptic substance which would destroy 

 the fermenting agent. Arsenic was found by Schwann to have this 

 germicidal property. Hence Schwann supported Latour's theory 



