Product Class: Other

NEB® 10-beta Electrocompetent E. coli

 Supplied with outgrowth medium optimized for NEB 10-beta & NEB Stable Competent E.coli ; please do not use SOC outgrowth medium.

Product Introduction

NEB 10-beta Competent E. coli is a derivative of the popular DH10B. It is T1 phage resistant and endonuclease I (endA1) deficient for high- quality plasmid preparations.

  • High efficiency strain ideal for cloning large plasmids and BACs
  • Available in chemically-competent format (single-use and 200 μl vials)
  • No dry ice surcharge on competent cell shipments
  • Outgrowth medium included
  • Free of animal products
  • Refer to our Electroporation Tips
Catalog # Size Concentration
C3020K 6.0 x 0.1 ml

Product Information



  • DH10B™ derivative
  • Accomodation of large plasmids including BAC and cosmid constructs
  • Efficient transformation of methylated DNA derived from eukaryotic sources and unmethylated DNA derived from PCR, cDNA and other sources
  • Activity of nonspecific endonuclease I eliminated for highest quality plasmid preparations (endA1)
  • Suitable for blue/white screening by α-complementation of the β-galactosidase gene (Φ80ΔlacZM15)
  • Reduced recombination of cloned DNA (recA)
  • Resistance to phage T1 (fhuA)
  • K-12 Strain
  • Free of animal products

Transformation Efficiency

> 2 x 1010 cfu/μg pUC19

NEB 10-beta electrocompetent E. coli cells are optimized for high efficiency transformation by electroporation. These cells are ideal for DNA library constructions and all cloning purposes.


Δ(ara-leu) 7697 araD139  fhuA ΔlacX74 galK16 galE15 e14-  Φ80dlacZΔM15  recA1 relA1 endA1 nupG  rpsL (StrR) rph spoT1 Δ(mrr-hsdRMS-mcrBC) 

This product is related to the following categories:
Cloning Competent Cell Strains Products
This product can be used in the following applications:

Reagents Supplied

Reagents Supplied

The following reagents are supplied with this product:

NEB # Component Name Component # Stored at (°C) Amount Concentration

Properties & Usage

Antibiotic for Plasmid Selection

Antibiotics for Plasmid Selection Working Concentration
Ampicillin 100 µg/ml
Carbenicillin 100 µg/ml
Chloramphenicol 33 µg/ml
Kanamycin 30 µg/ml
Tetracycline 15 µg/ml

Shipping Notes

  • Ships on dry ice

Antibiotic Resistance

  • str


Electroporation Tips:
  1. Electroporation cuvettes and microcentrifuge tubes should be pre-chilled on ice. 
  2. Electrocompetent cells should be thawed on ice and suspended well by carefully flicking the tubes. 
  3. Once DNA is added to the cells, electroporation can be carried out immediately. It is not necessary to incubate DNA with cells. The maximum recommended volume of a DNA solution to be added is 2.5 µl. Addition of a large volume of DNA decreases transformation efficiency. 
  4. Contaminants such as salts and proteins can lower electroporation efficiency. Ideally, DNA for transformation should be purified and suspended in water or TE. Transformation efficiency is more than10-fold lower for ligation mixtures than the control pUC19 plasmid due to the presence of ligase and salts. If used directly, ligation reactions should be heat-inactivated at 65°C for 20 min and then diluted 10-fold. For optimal results, spin columns (NEB #T1030) are recommended for cleanup of ligation reactions. 
  5. Electroporation conditions vary with different cuvettes and electroporators. If you are using electroporators or cuvettes not specified in the protocol, you may need to optimize the electroporation conditions. Cuvettes with 1mm gap are recommended (e.g. BTX Model 610/613 and Bio-Rad #165-2089). Higher voltage is required for cuvettes with 2 mm gap. 
  6. Arcing may occur due to high concentration of salts or air bubbles. 
  7. It is essential to add recovery medium to the cells immediately after electroporation. One minute delay can cause a 3-fold reduction in efficiency. 
  8. Cold and dry selection plates lead to lower transformation efficiency. Pre-warm plates at 37°C for 1 hour. Using 37°C pre-warmed recovery medium increases the efficiency by about 20%. 
  9. Refreeze unused cells in a dry ice/ethanol bath for 5 min and then store at -80°C. Do not use liquid nitrogen. Additional freeze-thaw cycles result in lower transformation efficiency.

Application Features

DNA Effects on Transformation Efficiency and Colony Output: Electroporation efficiency remains extremely high up to about 10 ng of input DNA, then decreases at higher DNA concentrations. Total colony output continues to increase with increasing DNA input up to at least 1 μg of puc19.

Product Notes

  1. STORAGE AND HANDLING: Competent cells should be stored at -80°C. Storage at -20°C will result in a significant decrease in transformation efficiency. Cells lose efficiency whenever they are warmed above -80°C, even if they do not thaw.

Protocols, Manuals & Usage


  1. Electroporation Protocol (C3020)

Usage & Guidelines

Tools & Resources

Selection Charts

Web Tools

FAQs & Troubleshooting


  1. How should I calculate the Electrotransformation efficiency (C3020)?
  2. What are the strain properties (C3020)?
  3. What type of competent cells are suitable for transformation of DNA constructs created using Gibson Assembly?
  4. What type of competent cells are suitable for transformation of DNA constructs created using NEBuilder HiFi DNA Assembly Master Mix?
  5. How should I store SOC Outgrowth Medium? The SOC I received with my competent cells recommends storage at either room temperature or 4°C, however, when I purchase it as a stand alone product, it recommends storing it at 4°C. Which is better?
  6. How should I store the NEB 10-beta/Stable Outgrowth Medium?
  7. How should fragments be prepared for assembly using NEBuilder HiFi?

Quality, Safety & Legal

Quality Assurance Statement

Quality Control tests are performed on each new lot of NEB product to meet the specifications designated for it. Specifications and individual lot data from the tests that are performed for this particular product can be found and downloaded on the Product Specification Sheet, Certificate of Analysis, data card or product manual. Further information regarding NEB product quality can be found here.


The Specification sheet is a document that includes the storage temperature, shelf life and the specifications designated for the product. The following file naming structure is used to name these document files: [Product Number]_[Size]_[Version]

Certificate Of Analysis

The Certificate of Analysis (COA) is a signed document that includes the storage temperature, expiration date and quality controls for an individual lot. The following file naming structure is used to name these document files: [Product Number]_[Size]_[Version]_[Lot Number]

Safety DataSheets

The following is a list of Safety Data Sheet (SDS) that apply to this product to help you use it safely.

Legal and Disclaimers

Products and content are covered by one or more patents, trademarks and/or copyrights owned or controlled by New England Biolabs, Inc (NEB). The use of trademark symbols does not necessarily indicate that the name is trademarked in the country where it is being read; it indicates where the content was originally developed. The use of this product may require the buyer to obtain additional third-party intellectual property rights for certain applications. For more information, please email

This product is intended for research purposes only. This product is not intended to be used for therapeutic or diagnostic purposes in humans or animals.

New England Biolabs (NEB) is committed to practicing ethical science – we believe it is our job as researchers to ask the important questions that when answered will help preserve our quality of life and the world that we live in. However, this research should always be done in safe and ethical manner. Learn more.