Enhanced eicosapentaenoic acid productivity in Microchloropsis salina through low-cost medium optimization and EMS-induced random mutagenesis
This study demonstrates that combining low-cost medium optimization with EMS-induced random mutagenesis significantly enhances eicosapentaenoic acid (EPA) productivity in the native marine microalga *Microchloropsis salina*, achieving a mutant strain with substantially higher biomass and EPA yields at a fraction of the nutrient cost compared to standard media.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer
The ocean is a vast source of life, but it is also a fragile one. For decades, the world has relied on fish oil to provide eicosapentaenoic acid, a vital nutrient known as EPA that supports heart and brain health in humans and feeds the global aquaculture industry. However, fishing for this resource is becoming increasingly difficult. Supplies fluctuate with the seasons, marine ecosystems face mounting pressure, and the oil itself can degrade or accumulate unwanted contaminants. Scientists have long looked to the microscopic world for an alternative. Tiny algae, which form the base of the ocean's food web, are natural factories for these fatty acids. They can be grown in controlled tanks, offering a steady supply without the environmental toll of industrial fishing. Yet, turning these microscopic organisms into a practical, affordable source of EPA has remained a stubborn challenge. The algae often grow too slowly, produce too little of the desired nutrient, or require expensive food to survive, making the final product too costly for widespread use.
In a recent study, researchers from Mokwon University in South Korea tackled this problem by combining two distinct approaches: finding the right algae and feeding it the right food. They began by searching the coastal waters of Geoje Island, looking for a native strain of microalgae that could thrive on a cheap, fertilizer-based diet. From the seawater, they isolated several candidates and identified one, a species called Microchloropsis salina, that showed a particular hunger for a low-cost nutrient mixture derived from agricultural fertilizer. This specific strain grew well when fed a simple solution of this fertilizer and sea salt, a combination the researchers named ES medium. This was a crucial first step, as it proved that a high-value nutrient could be produced without relying on the refined, expensive chemicals typically used in laboratory settings. The cost of the nutrients required to produce a single gram of EPA in this new medium was calculated to be nearly ten times lower than in standard laboratory recipes.
However, even the best algae has limits. The original strain, while efficient, did not produce enough EPA to be truly competitive. To push its performance further, the researchers turned to a classic technique known as random mutagenesis. They exposed the algae to a chemical agent that gently scrambled its genetic code, creating thousands of slight variations. From this pool of altered cells, they looked for those that had accidentally become better at their job. They grew these candidates in the low-cost medium and screened them for signs of success: faster growth, higher fat content, and a greater ability to produce the target nutrient. After several rounds of testing, one mutant stood out. The researchers designated this superior strain BSL(N)103-1.
When this new mutant was grown in the optimized low-cost medium, the results were striking. Over a ten-day period, the culture produced a massive amount of biomass, or total algal mass, reaching a concentration of 4.6 grams per liter. More importantly, the fat content within that biomass was exceptionally high, and the specific amount of EPA produced was significantly greater than what the original strain could achieve. The mutant produced EPA at a rate of 53.5 milligrams per liter every day, a figure that was nearly three times higher than the original strain grown in the same low-cost environment and almost four times higher than the original strain grown in standard, expensive food. The genetic makeup of this improved strain was also examined to understand what had changed. The researchers found over 1,500 differences in its DNA compared to the original, including nearly a hundred changes that were likely to have a major impact on how the cell functions. While the study did not pinpoint exactly which single change caused the improvement, the genetic map provides a list of candidates for future investigation.
The success of this project lies in how the researchers connected the dots between the organism and its environment. They did not simply try to force the algae to work harder; they first found a strain that naturally liked the cheap food, and then they improved that specific strain to thrive in it. The resulting mutant did not just grow faster; it also changed its internal chemistry, shifting its fatty acid profile to contain a higher proportion of the desired EPA. This approach demonstrates that sustainable production does not always require complex genetic engineering or expensive technology. By carefully matching a hardy, native organism with a simplified, economical diet and then using traditional breeding techniques to enhance its natural abilities, the team created a system that is both productive and affordable. The study concludes that this integrated strategy offers a viable path forward for producing essential nutrients from the sea, turning a microscopic alga into a reliable, low-cost source of health for the future.
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