You’ll often hear the words homofermenters and heterofermenters in the conversation about inoculants, but what do they actually mean?
Homofermenters
Homofermenters, when used in silage making, convert plant sugars into lactic acid. Lactic acid is the strongest of the acids found in silage and consequently creates the pH drop necessary for a good fermentation to take place. Additionally, by facilitating a fast drop in pH, homofermentative bacteria reduce not only dry matter losses but protein breakdown, too.
The fast drop in pH is achieved because homofermenters convert one mole of glucose or fructose into two moles of the high-strength lactic acid.
Homofermenters do nothing for aerobic stability. In fact, the lactic acid they produce can act as a substrate for the proliferation of yeasts which initiate aerobic instability on opening the clamp on opening the clamp.
Commonly used homofermenters are Lactobacillus plantarum, Pediococcus pentosaceus, Pediococcus acidilactici, Lactobacillus lactis, and Enterococcus faeceum.
Heterofermenters
Heterofermenters are used in silage making because they produce acetic acid and 1,2-propanediol which can inhibit yeasts and moulds. However, they do not add to the quality of the fermentation. The acetic acid produced by heterofermenters is a weaker acid than lactic acid and will slow down the decline in pH. As an alcohol, 1,2-propanediol has no effect on acidity.
Heterofermenters convert plant sugars to lactic acid, acetic acid, carbon dioxide and water – the carbon dioxide and water being dry matter loss.
Heterofermenters should not be used on wetter forages.
Commonly used heterofermenters are Lactobacillus buchneri, Lactobacillus brevis, Lactobacillus hilgardii, Lactobacillus keferi, and Lactobacillus diolivorans
The Combination Inoculant
Historically, when choosing an inoculant for AD feedstock use, where higher dry matters silages are more common, a combination of both homofermentative and heterofermentative bacteria has been used…
BUT there are more effective alternatives:
- Safesil – a patented, unique preservative which destroys rather than inhibits the unwanted micro-organisms, allowing the naturally occurring lactic acid bacteria to carry out the fermentation process unhindered.
- Activator Plus CA – a homofementative bacteria with a specific citrate which produces a more potent agent against yeasts and moulds than acetic acid but, importantly, creates no loss in dry matter in the process – unlike heterofermenters.