# End-of-fermentation cross-check

| BactoBox® skill level   | Time to complete (E. coli)          | Hands-on time       | Requirements                                                                                                                                                                                                 |
| ----------------------- | ----------------------------------- | ------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| :school\_satchel: Basic | :hourglass\_flowing\_sand: 24 hours | :stopwatch: 2 hours | <i class="fa-hard-drive">:hard-drive:</i> [7.6a](/encyclopedia/item-register/bactobox-r/bactobox-r-hardware-changelog.md) <i class="fa-floppy-disk">:floppy-disk:</i> [v2026.02a](/encyclopedia/software.md) |

Ever wondered if your fermentation process has more potential? Getting maximal CFU/mL is crucial for vaccines, probiotics, bio-stimulants, and live biotherapeutic products. A simple crosscheck at end-of-fermentation (EoF[^1]) may unveil critical insights that unlocks higher CFU/mL.&#x20;

## Cross-check BactoBox® and plate count results

The importance of harvest time is illustrated in the below *P. fluorescens* example.&#x20;

* In the cyan window, the cell concentration is practically identical to the concentration of culturable (cells \~ CFU). Harvesting **later** could potentially increase the CFU/mL of the final product.
* In the grey window the cell concentration is significantly higher than the proportion of culturable cells (cells > CFU). Harvesting **earlier** could potentially increase the CFU/mL of the final product.

<figure><img src="/files/d0rnamcB9QrukLYizNKt" alt=""><figcaption><p><em>P. fluorescens</em> growth curve tracked with BactoBox® (lavender) and plate counts (yellow). Cyan box highlights where cells and CFUs are within 50%. Grey box highlights region where cell concentration is significantly higher than CFUs. All measurements were done by three individual dilution series prior to measurements. Error bars reflect standard deviation.</p></figcaption></figure>

## Overview

In this step by step guide we will demonstrate how to crosscheck BactoBox® and CFU results. You will need a fresh EoF[^1] culture sample. This should preferably be from a bioreactor, but you can also simulate the process with a simple shake flask culture of *E. coli*.&#x20;

The overall steps in the workflow are given below.&#x20;

1. [Get things ready](/mpd/workflows/cross-check/get-things-ready.md)
2. [Create measurement group](/mpd/workflows/cross-check/create-measurement-group.md)
3. [Retrieve culture sample](/mpd/workflows/cross-check/retrieve-culture-sample.md)
4. [BactoBox measurements](/mpd/workflows/cross-check/bactobox-measurements.md)
5. [Calculate dilutions](/mpd/workflows/cross-check/calculations-for-plating.md)
6. [Plate dilutions](/mpd/workflows/cross-check/plate-dilutions.md)
7. [Count colonies](/mpd/workflows/cross-check/check-remaining-cultures.md)
8. [Cross-check data](/mpd/workflows/cross-check/cross-check-data.md)
9. [Summary](/mpd/workflows/cross-check/summary.md)

## Summary

With this introduction you are now ready to check if your bioprocess has higher potential. Next step is [Get things ready](/mpd/workflows/cross-check/get-things-ready.md).

[^1]: End-of-Fermentation


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