Question: what is the main function of the fermentation pathway

title: Fermentation
text: The acidity of lactic acid impedes biological processes ; this can be beneficial to the fermenting organism as it drives out competitors that are unadapted to the acidity ; as a result , the food will have a longer shelf life ( part of the reason foods are purposely fermented in the first place ) ; however , beyond a certain point , the acidity starts affecting the organism that produces it . The high concentration of lactic acid ( the final product of fermentation ) drives the equilibrium backwards ( Le Chatelier 's principle ) , decreasing the rate at which fermentation can occur , and slowing down growth . Ethanol , into which lactic acid can be easily converted , is volatile and will readily escape , allowing the reaction to proceed easily . CO is also produced , but it is only weakly acidic , and even more volatile than ethanol . Acetic acid ( another conversion product ) is acidic , and not as volatile as ethanol ; however , in the presence of limited oxygen , its creation from lactic acid releases additional energy . It is a lighter molecule than lactic acid , that forms fewer hydrogen bonds with its surroundings ( due to having fewer groups that can form such bonds ) , thus is more volatile and will also allow the reaction to move forward more quickly . If propionic acid , butyric acid , and longer monocarboxylic acids are produced ( see mixed acid fermentation ) , the amount of acidity produced per glucose consumed will decrease , as with ethanol , allowing faster growth .