Comparing Peptone Media Formulations on Growth E. coli

Comparing the Effect of Different Peptone Media Formulations on Growth of Various Strains of Escherichia coli

Jennifer FitzGerald, Maddy Riemenschneider, Hailley Cound, Thomas C. Marsh, Ph. D Chemistry Department, University of Saint Thomas, St. Paul, MN



Introduction: Peptones are proteins that have been partially digested by an enzyme, and are used in bacteriological media formulations to provide a source of nitrogen, amino acids, and carbohydrates.

The source of protein, the enzyme(s) used to digest the protein, as well as the method of hydrolysis used in production may differ among peptones. Companies that produce peptones must meet consumer needs and provide peptones to fit varying demands, such as being animal or animal by-product free, kosher, non-GMO, or free of certain allergens.

Along with the variation in composition of these peptones comes the question of performance: What effect does using these different peptones have on bacterial growth?

Methodology: Cultures were grown in liquid media using the various peptones obtained from Nu-tek Bioscience in their formulations, with amounts based on the total percent nitrogen. During this time, the absorbance at 600 nanometers of the cultures was monitored at certain time intervals using a spectrophotometer.  This allowed for the data to be plotted and compiled into comparative growth curves.

Escherichia coli

  • Some strains are harmless, some pathogenic , and can cause illness or even death, along with strains developed for lab use.
  • Easily culturable, genes are easy to manipulate, and has a well documented genome

Media Formulations:

For 100 mL Media:

50 mL 0.2% total N Peptone solution

20 mL 5x M9 Salts

5 mL 10% Glucose

25 mL Sterile Nanopure Water

Each component is sterilized separately using an autoclave on liquid cycle for 35 minutes.


Peptone Amino Nitrogen and Total Nitrogen:
Peptone % TN AN/TN Ratio
Soy Nu-tek HSP-A 7.6 0.41
Soy Competitor 1 9.2 0.21
Soy Competitor 2 9.2 0.25
Soy Competitor 3 10.2 0.24
Pea Nu-tek HPP-A 12.4 0.40
Nut-tek Soy-YE A 9.1 0.48
Nut-tek Soy-YE B 8.1 0.42
Nut-tek Soy-YE C 8.9 0.46
Amino Acid Comparison
Nu-Tek Soy 1 Peptone Nu-Tek Pea Peptone
Amino Acid Free (mg/g) Total (mg/g) Amino Acid Free (mg/g)
Aspartic Acid 6 45 Aspartic Acid 14
Cysteine NA 5 Cysteine NA
Serine 9 30 Serine 8
Tyrosine 5 15 Tyrosine 2
Glutamic Acid 15 85 Glutamic Acid 2
Valine 8 20 Valine 18
Glycine 2 20 Glycine 3
Methionine 4 5 Methionine 1
Histidine 6 15 Histidine 6
Lysine 16 30 Lysine 19
Arginine 14 40 Arginine 2
Isoleucine 9 20 Isoleucine 17
Threonine 5 20 Threonine 11
Leucine 19 30 Leucine 35
Alanine 5 20 Alanine 10
Phenylalanine 11 20 Phenylalanine 20
Total 137 445 Total 168


Growth Curves:



  • Nu-Tek Soy HSP-A media formulations resulted in the highest optical density across all strains of E. coli
  • Nu-Tek Pea grew to a significantly lower OD than Nu-Tek Soy across all strains
  • When Nu-Tek Pea was mixed with a lesser quality peptone, it raised the comparative growth levels of the competitor to an OD that was similar to Nu-Tek Pea.
  • The addition of yeast extract in a 1:1 blend with Nu-Tek Soy appeared to improve the media, but the difference wasn’t significant


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