Team:Nantes/Hardware

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- Bioreactor -

To get our enzymes, we’ve decided to cultivate our bacteria in a bioreactor. Considering that we want to maximize our production, we’ve decided to create a chemostat that will provide continuous production of our enzymes. A chemostat is a type of continuous bioreactor that keeps the micro-organisms in the growth phase in a constant growth phase using a continuous stream of buffer adding, and culturing medium evacuated from the container.

The Design

Our chemostat will have to provide optimal conditions for the E. coli bacteria, so we will need to have constant feedback on what’s going on inside. Several probes will then inform us of the following parameters :

O2 concentration : As bacteria E. coli have a better growth rate in an aerobic environment, we will make sure to have a constant O2 concentration.
CO2 concentration : it should be maintained low to avoid anoxia
pH : E. coli’s optimal pH is between 6.5 and 7.5
Temperature : the optimal growth-temperature of E. coli is 37°C

bioreactor circuit — **Fig. 1** Outputs and inputs of the system. Every piece of the system is connected to a computer, which will allow us to get a feedback on the system and to regulate the circuit in real-time.

Since those parameters need to be controlled, the chemostat will also have :

Oxygenation system : coupled with a pump, it will provide the optimal oxygen flow in the medium
Heat-belt : This system will maintain the temperature at 37°C
Agitation system : Agitation will enable to have a homogenous concentration (O2, CO2, Nutrients…) inside the chemostat
To control O2, we will use an injection system control by nanometer

bioreactor design — **Fig. 2** Schematic view of the bioreactor. A: Diagram of the bioreactor. B: Details of the cap

As the chemostat is a continuous culture bioreactor, it must have an inlet and an outlet. The volume of incoming matter will be equal to the volume of the outgoing matter. This system will be monitored with a controller as an Arduino card, coupled with Solenoid valves. The volume will be determined in function of the volume of culture and of the bacterial growth rate.

Moreover, we will add two catheters :

One in case we have to add an element directly in the bioreactor
One to take samples for measurement purposes (feedback on bacterial concentration)

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