Fermentation Techniques for Protein Quality Enhancement

Fermentation presents a versatile and sustainable approach to improving the nutritional and functional attributes of protein-rich substrates. By harnessing the metabolic activities of microorganisms—most commonly lactic acid bacteria, Bacillus species and mixed consortia—fermentation can hydrolyse storage proteins, diminish antinutritional compounds and generate bioactive peptides. Techniques range from submerged to solid‐state fermentation, often applied in single or multi‐stage formats, and tailored through parameters such as temperature, pH and substrate preparation. Two‐stage solid‐state fermentation has emerged as a means to sequentially optimise proteolysis and antioxidative potential, while water‐based or submerged fermentations allow precise control over microbial growth and by‐product formation. Across legumes, cereals and oilseed meals, fermentation not only enhances protein solubility and in vitro digestibility but also modulates secondary and tertiary structures, leading to improved techno‐functional properties such as emulsification, foaming and water retention. These advances hold global significance for developing plant‐based proteins that meet consumer demands for clean‐label foods, addressing food security and reducing reliance on chemical treatments or intensive processing.

Research from Nature Portfolio

A recent study examined the sequential steps involved in traditional natto production—soaking, boiling and fermentation—and quantified their effects on soybean protein bioavailability. Fermentation increased in vitro protein digestibility from below 50 % after boiling to over 50 % in the final product, driven by the accumulation of low‐molecular‐weight peptides and the liberation of essential amino acids. Concurrently, antioxidant indices of digested fractions rose up to fourfold, with the fermented fraction exhibiting the highest values at the end of simulated gastrointestinal digestion. These findings demonstrate how controlled microbial processing can augment both the nutritional and potential health‐promoting properties of legume proteins.

Research from all publishers

In 2023, two‐stage solid‐state fermentation of soybean meal using thermophilic Bacillus licheniformis strains markedly increased crude and soluble protein content while significantly reducing trypsin inhibitor activity. The second fermentation stage enriched antioxidant capacity and improved interfacial properties by promoting β‐sheet formation and reducing particle size, thus enhancing both nutritional value and functional performance in emulsions and foams. Another study combined air‐classification with spontaneous solid‐state fermentation of chickpea concentrates to produce a natural sourdough ingredient. Over 72 hours, α-galactosides were reduced by over 88 % and phytic acid by 17 %, while total phenolics increased by more than 100 %. The fermented chickpea fraction exhibited higher water‐holding capacity and a more balanced flavour profile, illustrating a clean‐label route to valorise legume fractions. A novel approach to lentil protein improvement involved forming lentil–casein complexes followed by water kefir fermentation. This dual strategy elevated protein solubility from around 58 % to over 86 %, increased negative surface charge and boosted in vitro digestibility from 76 % to above 86 %. Structural analyses revealed shifts in secondary and tertiary motifs, correlating with enhanced functional attributes such as emulsification stability and digestible essential amino acid release.

Fermentation Techniques for Protein Quality Enhancement publication trend

The graph below shows the total number of articles in fermentation techniques for protein quality enhancement across all publications each year (not limited to Nature Index journals).

Technical terms

Solid-state fermentation: A process in which microorganisms grow on moist solid substrates without free water, enabling high enzyme activity and limited energy inputs.

In vitro protein digestibility: A laboratory measurement simulating gastrointestinal conditions to estimate the proportion of protein broken down into absorbable peptides and amino acids.

Antinutritional factors: Naturally occurring compounds—such as trypsin inhibitors, phytic acid and oligosaccharides—that interfere with protein digestibility or mineral bioavailability.

Back-slopping: A traditional fermentation technique involving the repeated transfer of a small portion of fermented material to fresh substrate to inoculate successive batches.

References

1. Effect of single and two-stage fermentation on the antioxidative activity of soybean meal, and the structural and interfacial characteristics of its protein. LWT (2023).
2. Enhanced nutritional value of chickpea protein concentrate by dry separation and solid state fermentation. Innovative Food Science & Emerging Technologies (2020).
3. In vitro protein digestibility and biochemical characteristics of soaked, boiled and fermented soybeans. Scientific Reports (2021).
4. Improving the Functionality of Lentil–Casein Protein Complexes through Structural Interactions and Water Kefir-Assisted Fermentation. Fermentation (2023).