The plate count method is by far the most typical method for determining the number of viable bacteria in a sample and is therefore often quoted as the gold standard method for this purpose. Unfortunately, even for some of the fastest-growing bacteria, it typically takes more than 10 hours for colonies to appear to the naked eye. Plate counts, therefore, do not provide actionable here-and-now knowledge for fermentation processes.

OD600
Optical density at 600 nm (OD600) is one of the most frequently used proxy methods for plate counts, but it is well-known that there are pitfalls with this technique.

• OD600 provides a number with an arbitrary unit.
• OD600 does not differentiate between bacteria and other particles. If the medium contains a background of non-bacterial particles or a high background of dead cells, this could result in misleading results.
• Many bacteria produce pigments that absorb in the OD600 range. The pigment production can vary over time and therefore the OD600/CFU ratio will be inconsistent.

BactoBox
BactoBox represents a novel rapid microbiology alternative to track in-process fermentation samples and bacterial test suspensions. The data provided in the blog for an E. coli growth curve show that BactoBox detects growth sooner than OD600 and clearly provides more consistent correlations with plate counts.

Visit the SBT blog to read about

• Pitfalls and disadvantages of OD600
• Advantages of the BactoBox
• Head-to-head comparison between the BactoBox and OD600 methods
• BactoBox gives reliable bacterial concentrations in minutes 
• BactoBox detects growth earlier than the OD600 method
• BactoBox correlation with CFU is consistent over time
• BactoBox as a superior method for in-process bacterial samples

Contact SBT for more or click on the Request Information button below.