Microalgae Lipid Production via Respiratory Quotient Control
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Solution Overview
Problem
Industrial-scale production of microalgae biomass rich in lipids, particularly from the genus Chlorella, faces challenges in maintaining sensory quality due to oxidative rancidity of monounsaturated fatty acids, such as oleic acid, which results in undesirable flavors and colors, making it difficult to incorporate into diverse food products.
Innovation Solution
Controlling the availability of dissolved oxygen during the lipid accumulation stage by monitoring the respiratory quotient rather than partial oxygen pressure, ensuring sufficient oxygen supply while preventing oxidative degradation, thereby maintaining sensory quality by modulating oxygen transfer through gas analyzers and adjusting oxygen supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If oxygen supply is increased to meet microalga respiratory needs during industrial-scale cultivation, then growth and lipid accumulation are improved, but oxidative degradation of monounsaturated fatty acids increases leading to rancid flavors and poor sensory quality
Solution Approach 1:
The patent implements a feedback control system using a respiratory quotient (RQ) probe that continuously monitors the ratio of CO2 production to O2 consumption by microalgae. This RQ signal provides real-time feedback on the metabolic state of the culture, allowing the control system to adjust aeration and agitation parameters dynamically. By maintaining RQ within a specific range (0.8-1.2), the system optimizes lipid accumulation while preventing excessive oxygenation that would cause oxidative degradation of fatty acids and rancid flavor development.
Solution Approach 2:
The patent changes the control parameter from traditional dissolved oxygen concentration to respiratory quotient (RQ). This parameter change is critical because RQ directly reflects the metabolic state and lipid synthesis activity of microalgae. By controlling RQ rather than dissolved oxygen, the system can maintain optimal oxygen availability for lipid accumulation while avoiding supersaturation conditions that trigger oxidative degradation pathways. This parameter transformation resolves the contradiction between productivity and sensory quality.
2Measurement precision
If traditional dissolved oxygen control is used in industrial fermenters, then oxygen availability can be monitored, but the control is inaccurate due to hydrostatic pressure and mixing effects at industrial scale
Solution Approach 1:
The patent replaces the mechanical dissolved oxygen sensing system with a respiratory quotient measurement system. Instead of using electrochemical oxygen probes that are subject to hydrostatic pressure and mixing effects in large fermenters, the system uses gas analysis to measure CO2 and O2 consumption rates. This substitution eliminates the measurement inaccuracies inherent in traditional dissolved oxygen control at industrial scale, providing reliable metabolic state monitoring without being affected by fermenter size, depth, or mixing intensity.
3Quantity of substance
If microalgae biomass is produced with high lipid content through heterotrophic cultivation, then nutritional value is improved, but oxidative rancidity develops over time causing unacceptable sensory quality
Solution Approach 1:
The patent applies preliminary action by controlling the respiratory quotient during the lipid accumulation phase to prevent oxidative degradation before it occurs. By maintaining RQ within the optimal range (0.8-1.2) during heterotrophic cultivation, the system proactively prevents the formation of peroxides, hydroperoxides, and volatile oxidation products. This preliminary control ensures that high lipid content biomass is produced with inherently stable sensory quality, eliminating the need for post-production stabilization treatments and ensuring long-term storage stability.
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 process ensures the production of microalgae biomass with acceptable sensory quality, reducing the presence of undesirable compounds and maintaining a higher respiratory quotient, resulting in a product with improved flavor and color profiles, suitable for broader food product applications.
Implementation Method 1
monitoring the respiratory quotient of said microalgae
Implementation Method 2
control of the availability of dissolved oxygen in the fermenter
Implementation Method 3
oxidative degradation leads to: the formation of peroxides, hydroperoxides and volatile organic compounds with a rancid odor
Data Source
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AI summary
The invention relates to a method for fermentative production, on an industrial scale, of lipid-rich biomass of microalgae of the Chlorella genus having acceptable sensory properties, characterised in that the dissolved oxygen availability in the fermenter is controlled by tracking the respiratory quotient of said microalgae.