The mist bioreactor system consists of a glass vessel with stainless steel upper and lower lids. The vessel itself stands vertically on four legs. The thermoregulation system is located in the bioreactor’s lower lid. Level and temperature sensor ports are located on the bioreactor’s upper lid. The bioreactor is supplied with a LED jacket, a hydraulic spray nozzle, three sample holder plates and a ring sparger. Gas inlet/outlet ports are located on the bioreactors upper lid. The exhaust gas condenser is mounted on the upper part of the bioreactor to prevent unwanted liquid particle efflux from the vessels environment. The design of the condenser provides an option for the user to adjust its position for easier autoclaving. The condenser is supplied with an adjustable gas valve for pressure regulation inside the vessel.

Bioprocess controller

The bioprocess controller enables control, supervision and logging of essential process parameters during fermentation. The bioprocess controller consists of a peristaltic pump, gas mixing, thermostating and light control systems. The readings from sensors are displayed and logged on-line. Based on built-in control algorithms, sensor readings and values of individual parameters, which have been specified by the user prior/during fermentation (set-points), the control actions value is calculated and passed to the respective control element (heater, cooling water valve, base pump, acid pump, e.t.c.) to perform the respective parameter’s regulation. The bioprocess controller enables supervision and control of the following parameters:

  • Light intensity;
  • Light ON/OFF time periods;
  • Aeration gas composition;
  • Fermentation mediums pH value;
  • Spray nozzles operation mode (feeding rate);
  • Fermentation liquids condensate level in the bioreactor;
  • Circulation pump operation time;
  • Fermentation mediums supply rate (Pulse time);
  • Temperature in the bioreactor;
  • CO2 and O2 concentration in the exhaust gas;
  • Fermentation mediums conductivity.

Sterility

All mentioned parts of the bioreactor system (except the LED jacket) can be autoclaved to ensure the fermentation processes sterility. The aeration/exhaust gas is filtered to prevent process contamination.

Temperature control

A temperature sensor is installed in the bioreactor to monitor the temperatures value for further control implementation (e.g. thermostat control). The user can define a desired set-point for the temperatures value in the bioprocess controller. The temperatures regulation is implemented by supplying thermostated water to the bioreactors jacket, which is located in the bottom lid. The respective control elements (cold water valve, circulation pump and heater) are located in the bioprocess controller’s thermostat and are controlled via built-in control algorithms.

Light supply

The light supply is provided by a LED jacket, which is affixed to the bioreactors vessel. The light intensity can be adjusted through the bioprocess controlle either manually or by defining a desired light intensity profile for the duration of the fermentation. The user can specify time periods (Day or Night) for the light supply, during which it is switched ON/OFF.

Fog/mist supply

Fog/mist is supplied to the bioreactor via hydraulic spray nozzle, which is mounted on the bioreactors upper lid. The liquid from the fermentation mediums vessel is supplied to the nozzle by means of a peristaltic/gear pump. The desired droplet size can be adjustedby regulating the pressure (feeding rate) of the supplied liquid. The user can define ON/OFF periods for fog/mist supply in the bioprocess controller. The condensate level in the bioreactor is monitored using a level sensor. When a pre-defined condensate level is reached the excess fluid is transferred from the bioreactor via peristaltic pump back to the fermentation mediums vessel. The fermentation mediums vessel is supplied with pH, and conductivity sensors. The pH is maintained at a desired set-point value by supplying either base or acid solutions to the fermentation liquid via bioprocess controller’s pre-calibrated peristaltic pumps. To prevent particle sedimentation and concentration gradient formation during fermentation the medium is agitated during the process by a magnetic mixer. The pH, temperature, CO2, O2 and conductivity readings are displayed on the bioprocess controller’s screen during fermentation.

Sample holders

Three sample holders are installed in the bioreactors vessel, on which the inoculum is seeded in the beginning of the process. The sample plate is a sieve with a ventilation hole in the middle for fog/mist circulation purposes. The upper lid of the bioreactor is supplied with a large port for culture seeding.

Aeration

Aeration is performed through a ring sparger, which is installed in the bioreactors vessel. The aeration gas composition (CO2 concentration) and flow is manually/automatically regulated by the bioprocess controller’s gas mixing system and MFC (mass flow controller). The pressure in the bioreactor is monitored using a manometer, which is mounted on the bioreactors upper lid. The pressure can be manually adjusted by means of an adjustable gas valve, which is located on the exhaust gas condenser. The exhaust gas composition is monitored by means of a CO2 / O2 gas sensor.

Sensors

The bioreactor is supplied with various ports for sensor, medium/gas inlet or outlet installation. Level and temperature sensors are installed in the bioreactor to monitor the condensates level and the temperatures value for further control implementation (e.g. circulation pump control, thermostat control).

4 Mist bioreactor scheme