Two Stage Fermentation Raises Lysine 3.4 Fold in Faba Beans and 3.6 Fold in Rapeseed Meal

Researchers at the Technical University of Denmark and Aarhus University have shown that a two-stage microbial fermentation process can substantially increase the lysine content of plant protein ingredients.

The team worked with faba beans and rapeseed press cake, two materials already used in food and animal feed but limited by the balance of essential amino acids in their proteins.

In the first stage, Bacillus subtilis subsp. natto broke plant proteins into smaller components and released nitrogen sources that could be used by another microorganism.

The researchers then added Corynebacterium glutamicum, which used those nitrogen sources to produce lysine, one of the nine essential amino acids humans must obtain through diet.

After fermentation, lysine content increased 3.4 fold in faba beans and 3.6 fold in rapeseed meal, reaching 37.5 and 29 grams per kilogram of dry matter respectively.

The approach could make plant-based foods more nutritionally complete and could also improve animal feed efficiency by reducing the need to supply excess protein simply to meet amino acid requirements.

That is especially relevant in organic pig and poultry production, where synthetic amino acids are restricted and overfeeding protein can lead to higher nitrogen excretion.

The researchers are now working on similar approaches for two other essential amino acids, suggesting fermentation could become a broader tool for upgrading lower-cost plant protein streams.