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What are Yeast Peptones?

Yeast peptones are protein hydrolysates that allow for the growth of microorganisms in an animal and allergen-free culture media. Yeast peptones are a less widely known form of peptones that answers the need of safety and traceability of biopharma & probiotics industries.


  • Yeast peptones are produced through selective hydrolysis of Saccharomyces cerevisiae grown in standardized conditions that maximize their protein content (high-protein yeast).
  • Yeast peptones are commonly used in culture media as nitrogen sources for the growth of microorganisms, including fungus, yeast, and bacteria.
  • They can reach a composition similar to animal and vegetal peptones with specificities linked to the raw material.
  • Yeast peptones and yeast extracts differ both in how they are designed to target a specific composition.

What are peptones?

Peptones are partially hydrolyzed proteins obtained from a proteinaceous raw material such as milk product, animal tissue, plant sources and yeast.

The Merriam-Webster dictionary defines peptones as “any of various water-soluble products of partial hydrolysis of proteins.[i] Peptones can also be understood as “water-soluble protein hydrolysates, containing peptides, amino acids, and inorganic salts as well as other compounds, such as lipids, vitamins, and sugars.[ii]

To summarize, proteinaceous raw material is broken down chemically or enzymatically to produce a combination of amino acids and peptides during the hydrolysis process. Peptones are proteins broken down into smaller chains and free amino acids that occur as liquid, paste, powder, or granules. Usually, peptones are categorized by the type of raw material utilized:


  • Yeast Peptones: derived from yeast protein sources, typically from species like Saccharomyces cerevisiae.
  • Animal Peptones: derived from animal protein sources such as bovine tissues or milk, but also in rare cases can be made from fish or egg.
  • Vegetal Peptones: Derived from plant protein sources, such as soy, pea, or wheat.

Source: Procelys by Lesaffre

What are the similarities between yeast, animal, and vegetal peptones?

Yeast peptones are protein hydrolysates obtained by using primary grown high-protein yeasts as a raw material. The resulting solution is suitable for the formulation of dairy-free and allergen-free culture media adapted to the diversity of microorganisms grown in biotechnology industries.

Depending on the source of the proteins and the hydrolysis method employed, the degree of hydrolysis varies, meaning that the ratio of amino acids, dipeptides, tripeptides and polypeptides is specific to the solution. Molecular weight profiles (MWP) are commonly used to compare the composition of a peptone and the relative amount of free amino acids, small peptides, and polypeptides.

The diversity of peptones composition is illustrated here with the MWP obtained for different peptones available on the market : 

Source: Procelys by Lesaffre

When compared to vegetal and animal peptones, the molecular weight distribution of yeast peptones is very similar with less than 30% of free amino acids and more than 60% of small and mid-chain peptides.

Interestingly, the yeast peptone NuCel® 581 PW has a significantly higher amount of long chain peptides (>10kDa) when compared to casein peptone.

It has been shown that variations in peptide composition of the culture media impact the metabolism status of a starter (Proust et al. 2020) [iii]. Then, adapting the peptide content to both the microorganism and the expected activity is key for several biotech industries, including starter culture and probiotics. Considering different types of peptones is key for the design of cost-efficient process at industrial scale.

The characteristics of peptones go beyond the composition. As for any ingredient of a culture media, additional guarantees and specifications must be considered to meet market and regulatory expectations.

How are yeast peptones made?

Yeast peptones are typically produced through the specific hydrolysis of yeast proteins. This process involves breaking down the complex proteins present in yeast cells into simpler components like peptides and amino acids.

Depending on the intended use and the required properties of the yeast peptones, additional steps may be needed, or some steps may be eliminated in the process.

Source: Procelys by Lesaffre

What are yeast peptones used for?

Yeast peptones are used in the culture media formulation in various sectors including:

  • Biopharma
  • Diagnostic
  • Bioingredients
  • Food cultures and probiotics
  • Biological agriculture


Yeast peptones are a rich nitrogen source frequently used in culture media as a nutrient for the growth of microorganisms, including fungi and bacteria. They are rich in small-chain peptides and work synergistically with yeast extracts and other nitrogen sources.

Together NuCel® yeast peptones and yeast extracts can be used for the industrial production of a broad range of mesophilic and thermophilic lactic bacteria. They also sustain the growth, viability, and metabolic activity of lactic acid bacteria with complex nutritional requirements. This includes the industrial production of a broad range of Bifidobacteria. Additionally, together with yeast extracts, they can be used to optimize microbial cell viability.

ProCel® Yeast peptones are used to optimize the production of biopharmaceuticals such as biologicals (therapeutic proteins, vaccines, and hormones such as insulin), active pharmaceutical ingredients (API), and vitamins by recombinant and non-recombinant microorganisms.

Yeast peptones: a complementary addition to the peptones landscape.

With their unique balanced composition, yeast peptones serve as a key component for many different culture media on various microorganism species growth. On the one hand, they can be used synergistically with meat and vegetable peptones to increase biomass and microbial cell viability. On the other hand, they can serve as a replacement for these traditional peptones for producers who want to make their products animal (dairy-free) and allergen-free (gluten-free) while still ensuring optimal growth and cell viability.

Yeast peptones are truly changing the way peptones are used, opening new doors for the future!

[i] https://www.merriam-webster.com/dictionary/peptone

[i] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4649854/#B5

[iii] https://doi.org/10.1128/AEM.01446-20.