Portal U de A

By: Andrea Carolina Vargas Malagón, journalist at UdeA Communications Department 

Universidad de Antioquia developed a microalgae bioreactor system that captures carbon dioxide (CO₂) from urban air and produces biomass with the potential to optimize performance in sectors such as agriculture and food. This exercise in applied science integrates research, academic training, environmental stewardship, and expansion into the productive sector. 

This content comes from Alma Mater newspaper. » View PDF editions

This microalgae bioreactor system captures about 360 grams of CO₂ and produces approximately 150 grams of dry biomass. Photo: Courtesy  
 
Four large transparent cylinders filled with bubbling green water are strategically placed on one of the terraces of Universidad de Antioquia’s University Research Center (SIU) to receive sunlight for most of the day, are. The hues of green vary depending on the type of microalgae they host. 

This is a microalgae bioreactor system. Microalgae are photosynthetic, mostly aquatic, single-celled organisms capable of transforming solar energy into biomass. The system was developed by the Organic Chemistry of Natural Products research group, attached to the Faculty of Exact and Natural Sciences, with funding from the Ministry of Science, Technology and Innovation. This initiative harnesses the natural process of photosynthesis to mitigate polluting emissions while simultaneously producing biomass—renewable biological material—with applications in sectors such as agriculture, food, and even aquaculture. 

According to Natalia Herrera Loaiza, PhD in biology, professor at UdeA, and lead researcher on the project, the system consists of four bioreactors, each with a capacity of 70 liters. Inside, they house a suspension of microalgae that carries out photosynthesis upon receiving sunlight and CO₂, introduced through an aerator that directly connects to the surrounding air.  Photosynthesis is a process by which microalgae transform solar energy into chemical energy, capture carbon dioxide, and release oxygen.  

"After cultivating the microalgae, we wait about 30 days for it to grow sufficiently. Then, they are harvested, and the biomass is taken to the lab and freeze-dried, which means removing excess water until we get a green product used in various applications. From this dry biomass—which typically weighs around 50 grams per bioreactor—it is possible to estimate how much carbon dioxide was absorbed during the process. On average, the whole bioreactor system captures about 360 grams of CO₂ during that period," Herrera Loaiza explained. 

Although the amount of CO₂ captured by this bioreactor system may seem low compared to what an adult tree absorbs in the same period, this technology, developed at UdeA, shows how academia can contribute to the search for sustainable alternatives to the climate crisis. Initiatives like this, when replicated, could benefit cities like Medellín—which has faced persistent air quality problems for years—and, at the same time, advance the national goal of achieving carbon neutrality by 2050. 

The UdeA bioreactor system works with three microalgae —Chlorella vulgaris, Ankistrodesmus falcatus, and Tetradesmus dimorphus— and one cyanobacterium: Arthrospira platensis, commercially known as spirulina. 

In addition to being a strategy for mitigating polluting emissions, the bioreactor system has served as a training environment for undergraduate, master's, and doctoral students, who participate in different phases of the project: from microalgae cultivation and monitoring to biomass processing and its application in research with a sustainable focus. 

Using the material obtained, studies are being conducted on its potential applications, such as supplementing fish feed, creating a microalgae-based shampoo—to harness its cell growth properties—extracting a natural blue pigment with potential in the food industry, and isolating phytohormones—natural chemical compounds in plants that influence their growth—to evaluate the effects on the development of different plant species. 

"This bioreactor system functions like a biorefinery: It not only absorbs CO₂ from the urban environment, but also creates biomass and transforms it into useful, value-added products," said Herrera Loaiza. 

Microalgae to supplement fish feed: a commitment to sustainable aquaculture 

Andrea Llanes Angarita's project was among the research efforts that benefited from the microalgae bioreactor system. Andrea is an industrial and environmental microbiologist, a master's student in biology at UdeA, and a member of the Organic Chemistry of Natural Products research group. She used the biomass produced to evaluate its potential as a nutritional supplement in fish feed. 

The study was conducted with fingerlings of the genus Oreochromis —which includes species such as the red tilapia—to evaluate this biomass's nutritional potential. "For 30-day periods, the four strains of microalgae grown in the bioreactors were used as a supplement to the fish's diet to determine whether they had any impact on the fish’s growth and, if so, which of them provided the greatest benefits," explained Llanes Angarita. 

According to the researcher, during that time, the fish's diet was supplemented with different concentrations of each strain, and parameters such as weight and length were evaluated to establish differences in the animals’ development. 

The results showed that supplementation concentrations between 3% and 5% produced the highest yield. Moreover, the microalgae that most influenced fish growth were Arthrospira platensis, followed by Chlorella vulgaris," said Llanes Angarita, who added that an increase in the fish's appetite was also observed, which suggests good acceptance of the food supplement. 

"Fish also have taste —known as palatability— and this influenced the better acceptance of Arthrospira platensis. Being a cyanobacterium, its cell wall is not made of cellulose, which improves its consistency and makes it more palatable. We saw that, with the supplement, they ate more and there was less food waste, which also means less wasted money," Llanes Angarita argued. 

Besides their good acceptance by fish, microalgae have a high nutritional value: They are rich sources of protein, essential amino acids, fatty acids such as omega-3, vitamins, and minerals. According to Llanes Angarita, these qualities make them a sustainable alternative for producing aquaculture supplements, as they enable the biomass from bioreactors to be used without relying on ingredients of animal or plant origin, which typically have higher environmental costs. 

A green and sustainable synergy between science and business 

Besides its use in aquaculture, Ecosphaira—a Colombian biotechnology company that focuses on advancing the agricultural and environmental sectors and partners with Universidad de Antioquia on this project—also examined the biomass produced in microalgae bioreactors as a biostimulant for crops. According to Carlos Lopera Agudelo, an agricultural engineer with a master's degree in biological sciences and the manager of Ecosphaira, the goal was to see if this biomass could be turned into a source of organic carbon, a vital element for microbial life and plant growth in the soil. The study aimed to apply the biomass to rice and beans, which are common in human diets. 

Lopera Agudelo reported that the analysis showed microalgae had a significant biostimulant impact on the species evaluated. These exhibited higher germination rates, improved root development, a greater number of leaves, and increased plant weight. "Microalgae do provide minerals, but their greatest potential lies in the category of organic soil conditioners, as organic additives in agricultural production," he added. 

According to Lopera Agudelo, these types of solutions are viable and easily scalable. They can be developed by biotechnology companies or implemented directly on farms or in agricultural companies interested in producing their own biomass. Ultimately, this initiative aims for technologies like microalgae bioreactors to move beyond the academic realm and become effective and applicable tools. 

"This is a 100% scalable, 100% viable exercise. It's great that these solutions are being widely adopted in the agricultural industry because they are relevant, necessary, and represent an alternative to the current problems of soil quality and the urgent need for cleaner and more sustainable production. I am confident that the production costs are low compared to the benefits they can generate," said Lopera Agudelo. 

The development of such systems demonstrates Universidad de Antioquia's dedication to the Sustainable Development Goals (SDGs) through academic efforts and its ability and interest in creating applied science: knowledge aimed at social and environmental change.