The Biology of Microalgae
Author: Edward Tivnan
Microalgae is a confusing organism for biologists to classify because it acts like a plant but has no roots, stems or leaves. Its potential to be a highly efficient producer of, for example, renewable diesel, bioplastics,
pharmaceuticals, cosmetics and animal feed stock makes it an organism worth understanding. And, its high photosynthesis efficiency makes it an organism that cannot be ignored in the new climate smart agriculture.
Microalgae are unicellular, eukaryotic, phototrophic, and heterotrophic microorganisms that can be grown in “different climate conditions and aquatic habitats” (She, 2021,p.3). It is estimated that 200,000 to 800,000
microalgae species are in existence and are an important part of all freshwater and marine ecosystems (Miller, 2006, p.506). One type of microalgae, green algae, has cell walls and photosynthetic pigments that are identical to those of plants yet “lack true roots, stems and leaves” (Cohen 2022). As in plants, the green color comes from the large amount of chlorophyll pigments called pigment beds and other accessory
pigments such as carotenoid and phytochrome proteins.
The disproportionately high level of pigments allows green algae to have a high photosynthetic efficiency – more than 8%. By comparison, sugar cane is considered a high-efficiency commercial crop, but its photosynthetic efficiency is 1% to 2%.
Microalgae can grow 20% to 30% faster than traditional food crops and has no need to compete for arable lands. Aquaponic water is an ideal growing medium for microalgae food production. Because “microalgae accumulate large portions of lipids, carbohydrates, proteins, enzymes, and vitamins" (She, 2021, p.3), microalgae can be used as a highly nutritious, inexpensive feedstock for aquaponic fish thus replacing expensive commercial feedstocks. Their high content of protein and phenolic
compounds also makes them an excellent source of nutrients for human food. Microalgae can also be grown as an energy material for anaerobic biodigesters to produce electricity or as high value plant fertilizers for
aquaponic growers.
One of the economic challenges for microalgae producers is to identify low-cost extraction and harvesting methods. Nevertheless, microalgae have a huge potential to be a low-cost, high-quality food supplement and reliable biofuel that aquaponic growers likely will be eager to use. In climate smart agriculture, microalgae will also be a source of bioplastics, pharmaceuticals, food ingredients and supplements, cosmetics, and medicines not yet imagined!
REview
Summary
1. Microalgae nutritional content far exceeds current commercial plant crops.
2. Microalgae grows faster than traditional food crops and there is no need for arable lands.
3. Microalgae can potentially be used for new food supplements, cosmetics, pharmaceuticals, and other types of medicines.
Review Questions
Why are microalgae confusing organisms for biologists to classify? Give three examples.
Why is photosynthesis efficiency important?
Name three or more important food molecules that accumulate in microalgae cells.
Underlined Vocabulary Words
1. Renewable diesel: a fuel made from fats and oils such as soybean oil or canola oil.
2. Photosynthesis efficiency: the fraction of light energy converted into chemical energy during photosynthesis.
3. Climate smart agriculture: A set of agricultural practices and technologies which simultaneously boost productivity, enhance resilience and reduce GHG emissions.
4. Eukaryotic: cells which have a membrane-bound nucleus.
5. Phototrophic: organisms that contain chlorophyll and other light-sensitive pigments that capture solar energy.
6. Heterotrophic: organisms that eat other plants or animals for energy and nutrients.
7. Pigment beds: Large physically associated group of chloroplasts and other accessory pigments.
8. Carotenoids: Yellow, orange, and red organic pigments that are produced by plants and algae.
9. Phytochrome: A pigment that plants, and some bacteria and fungi, use to detect light.
Teachers Only
Review Questions Answers
Why are microalgae confusing organisms for Biologists to classify? Give three examples.
Answer: Because microalgae act like a plant but have no roots, stems, or leaves.
Why is photosynthesis efficiency important?
Answer: Because microalgae can grow 20% to 30% faster than traditional food crops.
Name three or more important food molecules that accumulate in microalgae cells.
Answer: Microalgae accumulate “large portions of lipids, carbohydrates, proteins, enzymes, and vitamins.”
