What role do lactic acid bacteria play in silage?

The microorganisms in silage, apart from soil contamination and added water, include several major groups attached to the plant raw material, such as lactic acid bacteria, enterobacteria, butyric acid bacteria, yeasts, molds and other microorganisms.

However, only lactic acid bacteria are beneficial. Lactic acid bacteria are the main microorganisms for making good-quality silage; they can break down the carbohydrates in silage and form lactic acid to cause lactic acid fermentation, and it is through the activity of lactic acid bacteria that the silage is preserved. Enterobacteria in silage are facultative anaerobes, mainly Escherichia coli and Aerobacter, and carry out heterolactic fermentation; although they also produce some lactic acid, they simultaneously produce large amounts of hydrogen and carbon dioxide, turning a considerable portion of the nutritionally valuable carbohydrates into something worthless.

The principle of ensiling is that the silage is compacted and sealed, so there is a lack of oxygen inside. After lactic acid bacteria ferment and break down the sugars, the carbon dioxide produced further expels the air, and the lactic acid they secrete makes the feed weakly acidic; a pH value between 3.5-4.2 can effectively inhibit the growth of other microorganisms. Finally, the lactic acid bacteria are also inhibited by the lactic acid they themselves produce, the fermentation process stops, and the feed enters stable storage. But at this point the loss of nutrients such as sugars in the raw material is not great.