Intended Use
Bacto Tryptone are used in preparing microbiological culture media.
Ingredients, where noted, meet United States Pharmacopeia (USP) performance specifications.
Summary and Explanation
The manufacturing process for an enzymatic digest of casein isnot as destructive as an acid hydrolysis. Thus, the casein is not broken down as completely into its constituent components. In many cases this makes for a more nutritious hydrolysate, especially
for those organisms that prefer peptides to amino acids.
Bacto Tryptone was developed by Difco Laboratories while investigating a peptone particularly suitable for the elaboration of indole by bacteria. It is also notable for the absence of detectable levels of carbohydrates. Bacto Tryptone has been used in conjunction with casamino acids in nutritional studies to determine amino acids vs. peptide utilization. It is included in standard methods applications and is listed in the reagent section of the USP as meeting the specifications for pancreatic digest of casein, a component in many of the media listed. The European Pharmacopoeia also lists pancreatic digest of casein as a component in many of the recommended media. Bacto Tryptone also works well in fermentation applications. It has been used successfully with commonly used organisms, such as Escherichia coli,13 as well as uncommon organisms, such as the diatom Nitzschia laevis.
User Quality Control
NOTE: Differences in the Identity Specifications and Cultural Response testing for media offered as both Difco™ and BBL™ brands may reflect differences in the development and testing of media for industrial and clinical applications, per the referenced publications.
Identity Specifications
Bacto™ Tryptone
Dehydrated Appearance: Light beige, free-flowing, homogeneous.
Solution: 1.0%, 2.0% and 10.0% solutions, soluble in purified water. 1.0% solution is very light to light amber, clear. 2.0% solution is light to medium amber, clear. 10.0% solution is medium to dark amber, clear to slightly opalescent,may have a slight precipitate.
Reaction of 2.0%
Solution at 25°C: pH 6.5-7.5
Principles of the Procedure
Bacto Tryptone are pancreatic digests of casein. Casein is the main milk protein and a rich source of amino acid nitrogen.
Cultural Response
Biochemical Reactions
Bacto™ Tryptone
Prepare a sterile solution as directed below. Adjust final pH to 7.2-7.4. Inoculate and incubate at 35 ± 2°C for 18-48 hours.
TEST / TEST SOLUTION / ORGANISM / ATCC™ / INOCULUM CFU / RESULT
Fermentable Carbohydrates 2% Escherichia coli 25922 ~107 Negative
Indole Production 0.1% Escherichia coli 29552 0.1 mL, undiluted Positive
Acetylmethylcarbinol Production 0.1% with 0.5% dextrose Enterobacter aerogenes 13048 0.1 mL, undiluted Positive
Hydrogen Sulfide Production 1% Salmonella enterica 14028 0.1 mL, undiluted Positive
subsp. enterica serotype Typhimurium
Growth Response
Bacto™ Casitone, Bacto™ Tryptone or BiTek™ Tryptone
Prepare a sterile solution with 2.0% Bacto Tryptone, 0.5% sodium chloride and 1.5% agar. Adjust final pH to 7.2-7.4. Inoculate and incubate plates at 35 ± 2°C for 18-48 hours.
ORGANISM / ATCC™ / INOCULUM CFU / RECOVERY
Escherichia coli / 25922 / 30-300 / Good
Staphylococcus aureus / 25923 / 30-300 / Good
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