Understanding Photobioreactors: Types, Applications, Pros & Cons, and Control Strategies
- Arun Luthra
- Jun 10
- 4 min read
As the world embraces sustainable biotechnologies, photobioreactors (PBRs) have emerged as vital tools in the cultivation of photosynthetic organisms like microalgae, cyanobacteria, and plant cells. These systems offer precise control over environmental factors and are widely used in sectors like biofuels, nutraceuticals, cosmetics, pharmaceuticals, and wastewater treatment.
What is a Photobioreactor?
A photobioreactor is a bioreactor that supplies light, either natural or artificial, to support the growth of photosynthetic organisms. The controlled environment allows optimal biomass productivity while minimizing contamination and resource wastage.
Types of Photobioreactors
Tubular Photobioreactor
Description: Comprises transparent tubes (usually glass or plastic) arranged horizontally or vertically, often in loops.
Pros: High surface area for light exposure, suitable for outdoor and large-scale operations.
Cons: Risk of biofouling, complex cleaning, and oxygen accumulation.
Ideal Applications: Outdoor cultivation for high-volume biomass such as biofuels and feedstock production.
Flat Panel Photobioreactor
Description: Features flat, transparent panels where culture flows in a thin layer.
Pros: Uniform light distribution, compact footprint, easier to clean than tubes.
Cons: Limited scalability, can suffer from temperature stratification.
Ideal Applications: Indoor production of high-value compounds like nutraceuticals, pharmaceuticals, and pigments.
Column (Bubble/ Airlift) Photobioreactor
Description: Cylindrical vertical reactors with air or gas injection to circulate the culture.
Pros: Efficient gas exchange, good mixing, compact design.
Cons: Lower surface area for light, limited light penetration in denser cultures.
Ideal Applications: Laboratory R&D, seed culture development, and specialty chemical production.
In Situ Photobioreactor
Description: Designed to integrate into the natural environment, often submerged or partially embedded systems.
Pros: Minimal energy input, mimics natural ecosystems.
Cons: Poor control over environmental conditions, low productivity.
Ideal Applications: Eco-restoration, educational projects, and low-cost biomass cultivation.
Applications of Photobioreactors
Industry | Applications |
Biofuels | Algae-based biodiesel, hydrogen production |
Nutraceuticals | Omega-3 fatty acids, antioxidants (e.g., astaxanthin) |
Pharmaceuticals | Therapeutic proteins, vaccines, and anti-cancer agents |
Cosmetics | Natural pigments, UV protectants, and anti-aging products |
Wastewater Treatment | Bioremediation, CO₂ capture, nutrient removal |
Food & Feed | Spirulina, Chlorella biomass, and alternative proteins |
Comparative Table: Photobioreactor Types
Type | Pros | Cons | Best Fit Application |
Tubular | High productivity, scalable | Biofouling, complex cleaning | Biofuel, large-scale biomass |
Flat Panel | Compact, good light distribution | Limited scalability, cost | Pharmaceuticals, pigments, nutraceuticals |
Column (Airlift) | Easy gas exchange, cost-effective for lab-scale | Lower light exposure | Lab-scale research, inoculum preparation |
In Situ | Energy-efficient, low-cost | Unpredictable control, low yields | Eco-restoration, educational applications |
Control Parameters in Photobioreactors
For optimal growth and product yield, PBRs require real-time monitoring and control of multiple parameters:
Light Intensity & Photoperiod Regulates photosynthetic activity; controlled via LEDs or sunlight filters.
Temperature is maintained using chillers or heating jackets, depending on the species' needs.
pH adjusted using CO₂ or alkali/acids to ensure metabolic efficiency.
Dissolved Oxygen (DO)Excess oxygen is removed via degassing or increased airflow.
Agitation and Mixing ensure uniform distribution of nutrients, gases, and light.
Nutrient Concentration is monitored and dosed based on growth phase and productivity targets.
Foam Control: Automated dosing of antifoam agents using foam sensors.
Which Photobioreactor is Right for You?
Goal | Recommended PBR Type |
High biomass for fuel/feed | Tubular |
High-value compounds in controlled settings | Flat Panel |
Lab-scale studies or strain screening | Column (Bubble/Airlift) |
Outdoor environmental integration | In Situ |
Education or low-tech culture | In Situ / Simple Column Designs |
Best-Fit Photobioreactor Types
Organism/Application | Best PBR Type | Reason |
Spirulina | Open Raceway or Tubular PBR | - Open raceways are cost-effective and widely used for Spirulina. - Tubular PBR offers better contamination control and higher productivity. |
Chlorella | Flat Panel or Tubular PBR | - Chlorella requires controlled light and CO₂ levels. - Flat panels offer better light utilization and easier cleaning. |
Alternative Proteins | Flat Panel or Tubular PBR | - For food-grade or pharma-grade biomass, closed systems ensure purity and compliance. - Flat panel PBRs are ideal for high-value protein cultivation. |
When Flat Panel PBRs are Suitable for Spirulina:
High-Purity Applications Spirulina is being produced for pharmaceutical, cosmetic, or high-grade nutraceutical applications. A flat panel PBR ensures:
Controlled contamination-free environment
Cleanability and compliance with GMP standards
Consistent product quality
Indoor Cultivation Flat panels are especially suited for indoor systems with artificial lighting, where light distribution, temperature, and gas composition can be finely controlled.
R&D and Strain Optimization for laboratory- and pilot-scale studies, where specific light wavelengths or conditions need to be tested.
Flat Panel Photobioreactor Design Specifications
Overall Design Concept
A vertically mounted transparent panel with a shallow depth to ensure maximum light penetration and effective gas exchange. Designed for closed-loop circulation, sterility, and optimal growth conditions.
Mechanical Design
Component | Specification |
Material | Autoclavable Acrylic (PMMA) / Borosilicate Glass / Polycarbonate |
Frame | Stainless Steel 304/316L with support legs and clamps |
Volume | ~250-280 Liters per panel |
Light Path Thickness | 20–50 mm for optimal light penetration |
Gaskets | Food-grade silicone or EPDM, US FDA 21 CFR compliant |
Ports | Inlet/outlet (TC 1.5"), pH, DO, temperature, sample port, foam sensor |
Lighting System
Parameter | Specification |
Type | LED panel (White, Red, Blue – tunable spectrum) |
Photoperiod | Programmable via PLC (e.g., 16:8 Light:Dark cycle) |
Intensity | fixed or adjustable |
Placement | Rear-lit or double-sided light panels |
Cooling | Forced air cooling or integrated liquid heat exchanger behind the LED |
Gas Exchange & Agitation
Component | Specification |
Aeration | Air/CO₂ mix through fine bubble sparger (0.2–0.5 vvm) |
CO₂ Delivery | Mass flow controller or solenoid valve with PID based on pH |
Agitation | Airlift, recirculation pump, shaft with impeller |
Degassing | Degassing membrane or headspace vent with a sterile filter as an option |
Sensors and Automation
Parameter | Sensor Type |
Temperature | PT100 RTD |
pH | Digital pH sensor |
DO | Optical DO sensor |
Foam | Conductivity-based or capacitance-based foam sensor |
Level | Non-contact ultrasonic level sensor |
Light Intensity | PAR sensor (optional) |
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