Agri-inputs & biocontrol
Silage biopreparations
The biochemistry of ensiling: homofermentative lactic acid bacteria and the pH drop that stops clostridia, and the dry-matter loss that Lactobacillus buchneri trades for aerobic stability.
Ensiling preserves wet forage by acidifying it under anaerobic conditions. Cut material keeps respiring until the oxygen in a sealed clamp is gone; fermentation then begins, and the only question is who ferments. Epiphytic lactic acid bacteria convert the crop’s water-soluble carbohydrates to lactic acid, pH falls, and below a low enough value the rest of the microflora stops. If sugar is short, or acid accumulates slowly, or the buffering capacity of the crop absorbs it, clostridia take over instead — Clostridium tyrobutyricum above all — fermenting lactic acid to butyric acid and degrading protein to amines and ammonia. Such silage loses energy and protein, and clostridial spores pass through the cow into milk, where they cause late blowing in hard cheese.
Why an inoculant works here
This is the rare microbial product whose introduced strain genuinely establishes, and the reason is structural: it is applied not into soil with a settled community but into fresh plant material where a niche has just opened — oxygen gone, competitors few, substrate abundant. Application rates on the order of 10⁵ CFU per gram of fresh forage are chosen so that the applied strain outnumbers the epiphytic population from the start, that population being variable on the standing crop and often small.
Homofermentative species — Lactiplantibacillus plantarum, formerly Lactobacillus plantarum, together with Pediococcus and Enterococcus faecium — run glycolysis to two lactate molecules per hexose with no CO₂ released. This is the efficient route: fast acidification, minimal dry matter loss, better protein preservation. The pH that must be reached depends on dry matter and buffering capacity: maize with its sugars drops below four easily, while legume forages with high buffering must be wilted first, since no inoculant will otherwise reach the target.
The trade Lactobacillus buchneri makes
Well-preserved silage is unstable in air. Once the clamp is opened, lactate-assimilating yeasts oxidise the accumulated acid, pH rises, the mass heats, and moulds and mycotoxins follow. The heterofermentative Lentilactobacillus buchneri addresses exactly this, and does it in an unusual way: under anaerobic conditions it slowly converts lactic acid that has already been formed into acetic acid and 1,2-propanediol. Acetic acid inhibits yeasts far more effectively than lactic acid does, and opened silage then holds for days rather than hours.
The cost is explicit and cannot be designed away: converting lactate to acetate releases CO₂, which is dry matter lost, and the final pH is higher than under purely homofermentative fermentation. The product also works slowly — the effect develops over weeks, so short storage never repays it. Hence the split in the product range: a homofermentative strain where preservation matters and feed-out is quick; buchneri or a mixture where a clamp is opened gradually in warm weather. In the EU these preparations are authorised as technological feed additives in the functional group of silage additives under Regulation (EC) No 1831/2003, assessed by EFSA strain by strain.