Selective Bioreactor Light Control for Microalgae Photoinhibition
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Solution Overview
Problem
Microalgae culture systems face challenges with light gradient issues, where cells near the light source are overexposed, while those deeper in the tank are underexposed, limiting production due to photoinhibition and non-photochemical dissipation, and existing solutions like genetic modification or nutritional stress selection are complex and yield monocultures with reduced robustness.
Innovation Solution
A bioreactor system with a light source, sensor, and controller that adjusts light intensity to induce cellular stress, allowing microalgae to adapt and become more translucent, thereby improving light penetration and reducing photoinhibition, while maintaining a culture medium concentration to select strains with increased resistance to photoinhibition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If microalgae density is increased in culture tanks, then biomass production is improved, but light penetration is reduced causing cells at the bottom to be left in darkness and cannot proliferate properly
Solution Approach 1:
The patent applies parameter changes by systematically varying light intensity parameters through sequential stress phases (increasing light intensity to induce stress) and relaxation phases (decreasing light intensity to allow recovery). This dynamic parameter adjustment enables high biomass density while maintaining sufficient light penetration through adaptive optical condition modulation.
Solution Approach 2:
The patent implements periodic action through cyclic alternation between stress phases (high light intensity exposure) and relaxation phases (reduced light intensity). This periodic modulation of light conditions allows cells to adapt to high density environments while periodically recovering from photoinhibition, thereby maintaining both high biomass production and adequate light penetration.
2Illumination intensity
If genetic modification is used to reduce collecting antennae size, then light penetration is improved, but the process becomes complex and expensive requiring mutation-selection methods
Solution Approach 1:
The patent replaces complex genetic engineering mechanisms with a simpler optical control mechanism. Instead of modifying microalgae genetics to reduce collecting antennae, the system uses controllable light sources with adjustable intensity to dynamically optimize light penetration through the culture medium, achieving the same effect without genetic manipulation complexity.
Solution Approach 2:
The patent changes optical parameters (light intensity, duration, spectral composition) rather than biological parameters (collecting antennae size). By modulating light delivery parameters through sequential stress and relaxation phases, the system achieves improved light penetration without requiring complex mutation-selection processes.
3Productivity
If high light intensity is applied continuously, then photoinhibition occurs reducing productivity, but reducing light intensity limits biomass production
Solution Approach 1:
The patent applies periodic action by cycling between stress phases (high light intensity that would cause photoinhibition if continuous) and relaxation phases (reduced light intensity allowing cellular recovery). This periodic modulation prevents accumulation of photodamage while maintaining high average light input for biomass production, thereby resolving the contradiction between productivity and photoinhibition avoidance.
Solution Approach 2:
The patent maintains continuity of useful action by ensuring that during relaxation phases, cells recover from photoinhibition stress, and during stress phases, biomass production is stimulated. The continuous cycling between these phases ensures uninterrupted productive activity at the population level, even though individual cells experience periodic stress and recovery.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The bioreactor system enhances biomass production by selecting microalgae strains that are more resistant to photoinhibition, allowing deeper cells to receive sufficient light, leading to increased transparency and improved productivity, even at low light intensities, and can maintain high productivity across varying light conditions.
Implementation Method 1
a light source capable of emitting light of an input intensity Iin to a tank
Implementation Method 2
a sensor arranged to measure an output light intensity Iout
Implementation Method 3
Microalgae have the capacity to capture light energy to fix and metabolize inorganic carbon from carbon dioxide (CO2) into energy-rich molecules
Data Source
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AI summary
The invention relates to a bioreactor including: a light source (200); a light sensor (300) facing said light source; a vat (100) that is placed between the light source (200) and the light sensor (300), said vat being intended to receive a culture medium comprising a cellular culture of photosynthetic microorganisms; a controller (400) connected to the light sensor (300) in order to control the vat (100) to obtain a chosen cellular-culture concentration (xi) in the culture medium during a working period, said light source (200) being capable of emitting incident light (L) of an input light intensity (Iin) in the direction of the vat (100), and the light sensor (300) being capable of measuring an output light intensity (Iout) and of transmitting data relating to this intensity (Iout) to the controller for the control of the vat; and a system (500) for controlling the light source (200), this system being arranged to adjust, during a period shorter than or equal to said working period, the input light intensity (Iin) to a setpoint value allowing a cellular stress to be induced in certain at least of said photosynthetic microorganisms.