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Advances in industrial harvesting techniques of edible microalgae

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By Milthon Lujan

Microalgae cultivation. Source: UNER.
Microalgae cultivation. Source: UNER.

Microalgae are causing a stir in the food industry because they are a rich source of proteins, lipids, vitamins, and pigments that can be used in food production.

But there’s a problem: these incredible microorganisms, despite their nutritional potential, are notoriously difficult to harvest.

A scientific review published by researchers from Yangzhou University, Kyushu Institute of Technology, Fukuoka Women’s University, and The University of Tokyo delves into the fascinating world of microalgae harvesting and showcases cutting-edge technologies addressing this challenge.

The study, the researchers report, “emphasizes green technologies and their potential for integration, stimulating innovation toward ecologically friendly microalgae harvesting while aligning process development with sustainable design principles.”

Traditional methods fall short

Various species of microalgae such as Arthrospira (Spirulina), Chlorella, Dunaliella, Haematococcus, Crypthecodinium, Schizochytrium, and Porphyridium have been used as supplements and food ingredients in a variety of products.

Efficient biomass harvest is crucial for using microalgae in food products and supplements. However, microalgae harvesting poses significant challenges.

Centrifuges, filters, and gravity sedimentation were once the preferred tools for collecting microalgae. But these methods have limitations: high costs, energy consumption, and aggressive chemicals that can affect nutritional quality, leading to the search for sustainable and low-cost alternatives to harvest microalgae.

Emerging technologies

The study describes emerging technologies for microalgae harvesting, including bioflocculation, electrolytic flocculation, ultrasonic aggregation, magnetic separation, and phototaxis.

Here’s a brief description of each technology:

  • Bioflocculation: Friendly bacteria or algal biopolymers are introduced to group the microalgae, making them easier to capture and process.
  • Electrolytic Flocculation: A current strikes the water, generating bubbles that attract and adhere to the algae, causing them to clump together and sink.
  • Ultrasonic Aggregation: High-frequency sound waves vibrate the water, causing microalgae to collide and stick together.
  • Magnetic Separation: Microalgae adorned with tiny magnetic particles are drawn to powerful magnets, carefully separating them from the water.
  • Phototaxis: Some algae species follow light. Strategically manipulating light sources can attract them to designated collection areas.
  • Hybrid Systems: Combining different technologies can leverage their strengths and overcome weaknesses, creating a dream harvesting team.
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Practical applications

New harvesting technologies offer a brighter future for the microalgae industry, with key applications including:

  • Safe for Food Use: No aggressive chemicals, meaning algae retain their nutritional benefits, ready to be transformed into delicious and healthy foods.
  • Energy Efficiency: Say goodbye to energy-consuming machines. These methods use less energy, making microalgae production even more environmentally friendly.
  • Scalable Solutions: From small-scale farms to large-scale operations, these technologies can adapt and grow with the industry.

Research needs

The path to using microalgae in the food industry presents many obstacles. To unlock their full potential, continuous research is needed in:

  • Material Optimization: Finding the perfect bioflocculants, magnetic particles, and light sources to maximize efficiency and smoothness.
  • Large-Scale Operation: Scaling up these technologies from the lab to the field, ensuring they work just as well in real-world environments.
  • Process Monitoring: Close monitoring of the harvesting process to optimize performance and avoid setbacks.
  • Techno-economic Analysis: Ensuring that the use of microalgae is not only good for the planet but also for business.

Conclusion

By adopting green technologies and fostering innovation, we can unlock the immense potential of microalgae as a sustainable food source for the future.

“The emerging microalgae harvesting technologies offer more sustainable separation pathways than conventional methods. Approaches like bioflocculation, electrolytic flocculation, magnetic separation, and phototaxis minimize the use of chemicals and energy inputs, reducing the environmental footprint,” the researchers concluded.

These emerging technologies offer a glimmer of hope to make microalgae a commercially viable food ingredient. With increased efficiency and reduced costs, microalgae can potentially address global food security concerns, provide sustainable nutrition, and even create new, delicious, and healthy food products.

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The study was funded by the National Natural Science Foundation of China, the High-Level Talent Introduction Fund of Yangzhou University, the Innovative Talent Program of “Golden Phoenix of the Green City”, the Research Fund of Sichuan Cuisine Development Research Center, Philosophy and Social Sciences Key Research Base of Sichuan Province.

Contact
Jiangyu Zhu
School of Food Science and Engineering
Yangzhou University
No. 196 Huayang West Road, Hanjiang District
Yangzhou 225127, China.
Email: zhu.jiangyu272@mail.kyutech.jp

Reference
Jiangyu Zhu, Minato Wakisaka, Taku Omura, Zhengfei Yang, Yongqi Yin, Weiming Fang. Advances in industrial harvesting techniques for edible microalgae: Recent insights into sustainable, efficient methods and future directions, Journal of Cleaner Production, 2024, 140626, ISSN 0959-6526, https://doi.org/10.1016/j.jclepro.2024.140626.

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