Microalgal Cultivation via Segmented Light and Dark Cycles

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Solution Overview

Problem

Existing microalgal cultivation methods, particularly autotrophic modes, face limitations in biomass productivity due to low photosynthetic efficiency after a light cycle, and mixotrophic modes encounter issues with inhibited organic carbon absorption, chlorophyll loss, and high organic carbon source costs.

Innovation Solution

A method involving sequential autotrophic and heterotrophic modes, where microalgae are cultivated in an autotrophic mode during the light cycle and a heterotrophic mode in the dark cycle, with an organic carbon source added during the dark cycle to maximize cell growth without overloading the photosynthetic receptor system.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If mixotrophic mode is used to improve biomass productivity, then biomass productivity increases, but organic carbon absorption is inhibited and chlorophyll is lost

Engineering Contradiction:

Improvebiomass productivityVSAvoidorganic carbon absorption and chlorophyll retention

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The cultivation process is divided into distinct temporal phases: autotrophic phase during light periods and heterotrophic phase during dark periods. This segmentation allows the microalgae to experience each mode separately rather than simultaneously, preventing the inhibitory effects observed in continuous mixotrophic culture while maintaining the productivity benefits of both modes

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system implements periodic switching between autotrophic and heterotrophic modes based on light/dark cycles. During light periods, autotrophic growth occurs with photosynthesis; during dark periods, heterotrophic growth occurs with organic carbon supplementation. This periodic action optimizes biomass productivity while avoiding the negative effects of continuous organic carbon presence

Inventive Principle:

Principle #19Periodic action

2Productivity

If continuous light and CO2 are supplied in autotrophic mode, then photosynthesis continues, but photosynthetic efficiency decreases after a predetermined time period

Engineering Contradiction:

Improvephotosynthetic efficiencyVSAvoidcontinuous light supply duration

Core Design Contradiction:

ProductivityVSDuration of action of moving object

Solution Approach 1:

The system uses periodic light/dark cycles to alternately activate autotrophic and heterotrophic modes. During light periods, autotrophic photosynthesis occurs; during dark periods, heterotrophic metabolism occurs. This periodic switching prevents photosynthetic efficiency degradation by providing rest periods and preventing continuous exposure to light and CO2

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

While light is stopped during dark periods halting photosynthesis, the system maintains continuous biomass production by switching to heterotrophic mode where organic carbon is metabolized for growth. This ensures continuous useful action in terms of biomass accumulation without the diminishing returns of continuous photosynthesis

Inventive Principle:

Principle #20Continuity of useful action

3Productivity

If high concentration organic carbon source is supplied in mixotrophic mode, then biomass productivity improves, but supply cost increases and absorption is inhibited

Engineering Contradiction:

Improvebiomass productivityVSAvoidsupply cost and absorption efficiency

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

Organic carbon supplementation is segmented to occur only during dark periods when heterotrophic mode is active, not continuously as in mixotrophic culture. This timing segmentation improves absorption efficiency by avoiding the inhibitory effects of simultaneous light exposure and organic carbon presence, while reducing overall supply costs by limiting supplementation to necessary periods

Inventive Principle:

Principle #1Segmentation

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

This approach enhances biomass productivity, avoids the drawbacks of mixotrophic modes, and maintains carbon fixation efficiency, allowing for economic feasibility by using low organic carbon source concentrations, potentially sourced from wastewaters.

Implementation Method 1

an autotrophic mode, where carbon is fixed from an inorganic carbon source through photosynthesis

Methodology Applied

Scientific EffectPhotosynthesis: Photosynthesis

Implementation Method 2

a heterotrophic mode, where energy required for cellular activity is obtained from an organic carbon source through respiration

Methodology Applied

Scientific EffectRespiration: Aerobic Digestion

Data Source

PatentEP4047080A1Method for microalgal cultivation

Publication Date: 2022.08.24 KOREA UNIV RES & BUSINESS FOUND

Figure 1a~1b
Figure 2a~2b
Figure 2c~2d

AI summary

Disclosed is a method for microalgal cultivation. The method includes cultivating a microalgal species in a medium in an autotrophic mode for a predetermined first time period where light is supplied and supplying an organic carbon source to the medium to cultivate the microalgal species in a heterotrophic mode for a predetermined second time period where the supply of light is stopped.