Technical Guide
All three formulations share the same ingredients and differ by a single number, but that number decides whether your experiment succeeds.
ST BIO Technical Team
2026
For: Biotechnology researchers and laboratory purchasing staff
Key takeaways:
- Miller (10 g/L NaCl): the most versatile formulation, suitable for most E. coli work
- Lennox (5 g/L NaCl): low salt, suitable for electroporation and salt-sensitive strains
- Miller #4 (0 g/L NaCl): salt-free, for specialized experimental conditions
- Not sure which to choose? Default to Miller, which covers 99% of standard protocols
What Is LB Broth?
LB Broth (Lysogeny Broth) is the most widely used basal liquid culture medium in microbiology laboratories worldwide. Developed by Giuseppe Bertani in 1951, it was designed specifically for Escherichia coli and its recombinant strains. The three main formulations, Miller, Lennox and Miller #4, have exactly the same ingredients and differ in only one number: the NaCl concentration.
Tryptone supplies carbon and nitrogen, yeast extract supplies vitamins (including the B group) and trace elements, and NaCl maintains osmotic balance and the ionic environment. Together they support rapid cell growth, making LB the basal medium of choice for transformation, pre-expression culture scale-up and routine cultivation.
The Three Formulations at a Glance
Miller
LB Broth Miller
10 g/L NaCl
- Routine E. coli cultivation
- Chemical transformation recovery
- Culture scale-up before protein expression
- Culture scale-up before plasmid extraction
Lennox
LB Broth Lennox
5 g/L NaCl
- Electroporation
- Cultivation of salt-sensitive strains
- Experiments requiring low salt
- Specific downstream purification steps
Miller #4
LB Broth Miller #4
0 g/L NaCl
- Salt-free experimental conditions
- Special strain requirements
- Base for custom medium formulations
- Experiments sensitive to ionic strength
Detailed Specification Comparison
| Specification | Miller (standard) | Lennox (low salt) | Miller #4 (salt-free) |
|---|---|---|---|
| Tryptone | 10 g/L | 10 g/L | 10 g/L |
| Yeast Extract | 5 g/L | 5 g/L | 5 g/L |
| NaCl | 10 g/L | 5 g/L | 0 g/L |
| Amount dissolved per liter | 25 g/L | 20 g/L | 15 g/L |
| Chemical transformation | Best choice | Suitable | Rarely used |
| Electroporation | Not recommended | Best choice | Suitable |
| Routine E. coli cultivation | Best choice | Suitable | Rarely used |
| Frequency of use | Most common | Second most common | Special cases |
Each Formulation in Detail
Miller Formulation (10 g/L NaCl): The Default Choice
Miller has the highest NaCl concentration of the three and is the most widely cited standard formulation worldwide. The vast majority of molecular biology manuals (including Sambrook's Molecular Cloning) use the Miller formulation by default. If your protocol does not specify otherwise, choose Miller.
Suitable applications: routine E. coli cultivation and passaging, the recovery step after heat-shock chemical transformation (37°C, 45–60 minutes), strain scale-up before protein expression, and liquid culture scale-up before plasmid extraction.
Lennox Formulation (5 g/L NaCl): The Choice for Electroporation
The Lennox formulation halves the NaCl and is used mainly in two situations. The first is electroporation: electroporators are highly sensitive to conductivity, and high-salt media increase the risk of arcing, which the low-salt Lennox formulation helps to reduce. The second is certain special strains that are sensitive to high osmotic pressure and grow poorly in high-salt conditions; Lennox provides a gentler osmotic environment.
Miller #4 Formulation (0 g/L NaCl): For Special Salt-Free Requirements
Miller #4 contains no NaCl at all and is the least frequently used of the three. It is intended mainly for special experimental conditions that require very low ionic strength, or as a base for other medium formulations. Unless your protocol specifically calls for salt-free conditions, you usually do not need this one.
Quick Selection Guide
Choose according to your experimental conditions
Routine E. coli cultivation, heat-shock chemical transformation
→ Miller
Electroporation
→ Lennox
Strain is sensitive to high osmotic pressure
→ Lennox
Experiment requires salt-free conditions
→ Miller #4
Halal-compliant purchasing required
→ Halal-certified version (H)
Not sure, protocol does not specify
→ Miller (default)
Food-Grade vs Lab-Grade: Also Worth Checking When Purchasing
Most LB Broth suppliers on the market (including major international brands) use lab-grade raw materials, which are held to lower standards for heavy metal residues, microbial contamination control and raw material traceability, and are suited to pure research use. ST BIO's LB Broth series is made entirely from food-grade raw materials and produced in an ISO 22000-certified facility, making it suitable for food microbiology testing laboratories, biotechnology manufacturers that need raw material traceability documentation, and organizations with ESG or Halal compliance requirements for their supply chain.
ST BIO LB Broth Product Line
LB Broth Miller (19415): Food-grade standard version. View product → LB Broth Miller H (21621H): Halal-certified version. View product → LB Broth Lennox H (21620H): Low-salt Halal-certified version. View product → LB Broth Miller #4 H (21130H): Salt-free Halal-certified version. View product →
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