This project details the construction of a "Smart Bioreactor" designed to maintain a living yeast culture indefinitely. It uses a vacuum-distillation process at 30°C to harvest ethanol without heat-stressing the biological culture, managed by an ESP-32 controller.
Environment: Maintain temperature at 30°C and vacuum at ~500-800 mbar (low vacuum).
Monitoring: The ESP-32 monitors the duty cycle of the vacuum pump. As the yeast produces , the pressure rises, triggering the pump.
Transition: If the pump does not trigger for a predefined duration (X minutes), the controller assumes the sugar source is depleted.
Environment: Maintain temperature at 30°C and increase vacuum to ~65 mbar (28.0 inHg).
Action: Activate the condenser cooling pump and the vacuum pump. Ethanol begins to boil at 30°C.
Monitoring: The controller monitors the Differential Weight of the chamber. Once the weight loss reaches the calculated "Ethanol Target," the harvest is complete.
Action: Deactivate vacuum pump. Toggle a 3-way motorized valve to connect the feed tank to the chamber.
Monitoring: The vacuum inside the chamber pulls the sterile syrup in. The ESP-32 monitors the Feed Tank weight loss or Chamber weight gain.
Transition: Once the "Replacement Target" is reached, the valve closes, and the system resets to Phase I.
To achieve high precision on a heavy vessel, we utilize a Zero-Suppression rigging system:
Chamber Suspension: The 5-gallon chamber is suspended by a cable.
Counterbalance: A weight nearly equal to the "full" vessel weight is placed on the opposite side of a pulley.
Sensor: An S-Type Load Cell is placed in-line with the cable. It only "sees" the delta (0-10 lbs), allowing for milligram-level resolution of loss and ethanol stripping.
| Item | Description | Link |
| Vacuum Chamber | 5-Gallon Stainless Steel with Tempered Glass lid. | BACOENG 5 Gallon 4.5 CFM Tempered Glass Lid Vacuum Chamber |
| Vacuum Pump | 2-Stage, 5 CFM pump for deep vacuum stripping. | Pump |
| Graham Condenser | Glass trap to condense ethanol and protect pump. | StonyLab Borosilicate Glass Graham Condenser |
| Heating & Stirring | Wrap-around heater with thermostat and stirrer. | Powerblanket 5-Gallon Bucket Heater |
| Item | Description | Link |
| S-Beam Load Cell | 10kg Alloy Steel tension sensor (IP65). | Double Bolt Force Sensor Mini Load Cell 200kg |
| Vacuum Transducer | -100kPa to 0kPa, 0-5V Output Pressure Sensor. | 0-5V Output Vacuum Sensor |
| Temp Sensor | PT1000 for high-precision thermal monitoring. | Waterproof RTD PT100 Temperature Sensor |
| Load Cell Amp | 24-bit HX711 for digital weight translation. | HX711 24-Bit Precision Weighing Detector Seins0r Module-AD Converter for Electronic Scales |
| Item | Description | Link |
| Motorized Valve | 3-Way stainless steel ball valve for feeding. | U.S. Solid 1/2" 3-Way Motorized Ball Valve |
| Solid State Relays | 10A SSR for spark-free AC pump and heater control. | Fotek SSR-10 DA |
| Sterile Filter | 0.22-micron filter for the vacuum vent line. | Millex-GV 0.22 µm Sterile Filter |
Sterility: All air intake must pass through the HEPA filter. Sugar syrup must be boiled/cooled before being pulled into the chamber via the vacuum differential.
Fail-Safe: If the PT1000 detects a temp >35°C, the ESP-32 must cut power to the heater relay immediately to save the culture.
Anti-Bumping: The controller can pulse the vacuum pump to prevent a "flash boil" that would send foam into the cold trap.
In this alternative operating mode, the vacuum bioreactor vessel is repurposed as a Photobioreactor designed to cultivate Spirulina that yields biologically active Vitamin B12. This eliminates the need for vacuum-extraction of ethanol and shifts the physical requirements toward precise light-spectrum control.
keystone project's fish-barn-plan.md as a high-value, locally produced feed additive, fulfilling the B-complex vitamin requirements of the aquaponics system without external purchases.