APPLICATIONS / TURBIDOSTAT
What is a Turbidostat?
A turbidostat is a continuous culture system designed to maintain microbial cells at a constant cell density by dynamically adjusting the rate of fresh media addition.
Unlike batch or fed-batch systems, where growth conditions change over time, a turbidostat maintains cells in a steady-state growth phase.
This is achieved through real-time optical density (OD) measurement and automated feedback control.
When cell density exceeds a predefined threshold, fresh media is added, diluting the culture and restoring it to the target density.
Why use a Turbidostat?
A turbidostat provides a powerful way to decouple growth from time, enabling experiments that require microbes at specific states to be more reproducible, controlled, and information-rich.
As microbial cultures expand the cells experience different stresses which impact on their metabolism and their physiology.
Many experiments require microbes that are at very well defined and controlled cell states, such as studies into;
- Infection biology
- Microbial physiology
- Microbial Evolution (See also the Morbidostat application)
- Protein expression optimisation
- Bacteriophage production
Maintaining cultures at specific points in their growth can be undertaken in shake flasks but this requires very regular sampling and the inevitable dilution steps when cultures over-shoot, all of which is very time consuming as well as introducing variability and contamination risk.
An alternative is to employ a larger-scale bioreactor system but these are typically complex and costly to use.
Ogi3 completely automates the running of turbidostatic cultures in only 15 mL culture volumes minimising the costs and time involved while enabling users to have their cells are in the perfect state and available ‘on-tap’ when they are ready to use them.
How does a turbidostat work?
Each Ogi3 Reactor Flask is connected to two 500 mL laboratory bottles, one containing fresh culture media, e.g. LB, and the other being for removed ‘waste’ culture material, using lengths of peristaltic pump tubing and Media/Waste Stoppers.
When an experiment is configured a target OD can be set for each of the four reactor flasks in the system. As the culture grows the OD is measured as frequently as every 3 minutes. When the OD of a culture exceeds the target OD the feed and drain pumps are activated to supply fresh culture media to the culture while removing excess volume which dilutes the culture while maintaining a culture volume of 15 mL in the reactor flask.
After each pumping action the OD of the culture is checked and, if needed, the pumping action will be repeated until the OD falls below the threshold. This process is repeated for the duration of the experiment.
For each of the 4 flasks in an Ogi3 Bioreactor a target Optical Density (OD) can be specified, in this example the three cultures are to be maintained at ODs of 0.3, 0.7 and 1.0 as shown my the blue, orange and green lines.
Close-up: The red dots show OD measurements being taken every 5 minutes. When the OD exceeds the desired threshold the feed and drain pumps are triggered which reduces the OD to below the threshold.
Want to find out how you could use a turbidostat?
What else can an Ogi3 do?
Bang-Bang Turbidostat
Automate the process of generating growth curves by repeatedly growing cells across a defined portion of their growth curve under repeated or varied conditions.
Chemostat
Provide a consistent growth environment for your cells by continuously feeding them with fresh culture media.
Morbidostat
Automatic and dynamic stressing of cells for Directed Evolution (DE) / Adaptive Laboratory Evolution (ALE) experiments
Batch Culture
Automate the experiments you’re doing in shake flasks with the added real time analytics and control you need to get robust datasets with minimal hands-on time to maximise your productivity.
Build the perfect OGI3 for your experiments
OGI3 Bioreactor
Four independent bioreactors with precise control over stir speed, temperature, and optical density measurements.
Liquid Control Module
Effortlessly manage your liquid cultures with ogibiotec’s liquid control module.
Fluorescence Module
Enables real-time full spectrum scan of 340 to 780 nm in 2 nm increments.
pH Module
Monitor the pH in each culture. Ogi3 pH probes to allow the accurate measurement of pH 0-14.
Dissolved Oxygen Module
Measure the concentration of Oxygen in your cultures in real time.
Sparging Module
Provide additional gas to your cultures via headspace or dip-tube sparging. Supplied with pre-humidification units.
NB: Images not to scale