CHAPTER XVII 

 INDUSTRIAL FERMENTATIONS 



IN recent years there has been a very considerable 

 expansion of the use of micro-organisms in industrial 

 processes, largely due to a realisation of the variety of 

 catalytic properties possessed by their enzyme systems. 

 Many uses of bacteria and yeasts in industry, it is true, 

 date back to time immemorial ; it is only necessary to 

 mention the production of alcoholic beverages of all sorts, 

 baking, tanning and the retting of flax and hemp in order 

 that this may be realised. 



The Production of Glycerol by Fermentation. — As we 

 have seen, glycerol is a normal product in alcoholic 

 fermentation, where it occurs to the extent of about 

 3 to 4 per cent. During the 1914-1918 war period 

 Connstein and Liidecke, in Germany, added sulphite and 

 bisulphite to sugar solutions fermented by Saccharomyces 

 cerevisice and obtained much increased yields of glycerol, 

 which ran parallel with the amount of acetaldehyde 

 fixed by the sulphite (which is probably converted to 

 bisulphite by the action of carbon dioxide). As the 

 sulphite solutions are strongly alkaline, and since the 

 alkalinity increases during fermentation by production 

 of sodium bicarbonate, the medium soon becomes un- 

 suitable for continued fermentation, and recovery yields 

 of about 25 per cent, of glycerol are obtained. This 

 difficulty was overcome to a certain extent in Great 

 Britain by the use of a mixture of approximately equi- 

 molecular proportions of sodium sulphite and sodium 

 bisulphite which l)uffers the solution at about pTL 7. The 

 yield is about 30 to 35 per cent. 



