In order to maximize the convenience of the optogenetic automated control system, we designed an equipment to provide the most suitable growth environment for yeast. Except the Arduino microcontroller, the equipment is divided into three modules: light control and constant turbidity module, constant temperature module and continuous fermentation module.
In the light control and constant turbidity module, we used light sensor and a 1W 620nm LED to assemble a turbidimeter. First, a cell counter and a spectrophotometer were used to obtain number of the cell in the dry-yeast-powder-dissolved culture medium. Then the yeast-containing medium was serial diluted to obtain its 620nm light absorbance and the corresponding relationship between the number of yeast cells in the fermentation broth and its OD value. Therefore, the intensity of the 620nm light passing through the container can be approximately corresponded with OD value. In order to prevent the 620nm light from activating the light control system to a certain extent, we set the light turbidity detection to perform a short measurement every 10 minutes. When the OD value reaches 2 in three consecutive tests, the 525nm green LED will turn on, allowing the yeast to enter the dsRNA production stage.
In the constant temperature module, we use a 14W film heater and DS18B20 temperature sensor to maintain a constant temperature of the container. When the temperature is higher than the temperature set, the heater will automatically turn off. The temperature setting can be easily modified by changing variable in the program.
In the continuous fermentation module, two buttons and two peristaltic pumps were set to form two control group. One group is responsible for pumping out part of the fermented product and pumping some medium in for supplementation, while the other group is used to pump out a little part of the liquid for sampling, which could be convenient for detecting the number of yeast and the concentration of dsRNA in the cell.
The magnetic stirrer is normal open and operate independently, without automatic control.
To learn more about how our optogenetic automated control system. click link below and see:https://github.com/Tarelku/CAU_iGEM_2020_device