Powerful microalgae

Powerful microalgae

By Pablo Roset

Like the rest of the world, our country has a growing interest in the development of environmentally friendly technologies. In this sense, since 2008, researchers from the Faculty of Agronomy of the UBA (FAUBA) have been working with a view to exploiting the potential of microalgae (single-cell plants), either from the pure scientific interest or from the transfer of this technology. Its uses are multiple; among others, cleaning up polluted water, generating energy and obtaining by-products of high commercial value (such as certain antioxidants and colorants that are worth hundreds of dollars per gram).

“The Agroenergy Directorate, which depends on the Ministry of Agroindustry, called us together with other researchers from different public-private institutions in the country who also work on the issue of microalgae. This is how the Network of Microalgae of Argentina arose, with members from all over the country ”, Juan Gori, professor of the Biochemistry department at FAUBA, told the scientific outreach site Sobre La Tierra.

Within the framework of the network, Gori and a group of colleagues received training from the Ministry of Science and Technology, and thus the Microalgae Technology Watch Antenna was born. This 'antenna' collects information in three main branches of interest: bioprocesses (that is, different ways of cultivating and / or harvesting microalgae), bioremediation and bioproducts (everything we can obtain from them: biodiesel, bioethanol, alternative energies, carbohydrates, proteins, vitamins and antioxidant compounds and high added value colorants). “Certain molecules produced by microalgae, such as astaxanthin, a very important antioxidant, currently have a commercial value of more than US $ S7000 per kilo. By adjusting the technology, its production is possible ”, the researcher stated.

It sounds cruel: for microalgae to produce compounds of high commercial value, such as those already mentioned, they have to be stressed. “Production has two pillars. On the one hand, we stimulate them in a controlled environment so that they multiply and produce a lot of living material (we call it biomass). On the other, we generate some kind of stress for them by changing their environment. We achieve this by transferring them from the contaminated water to another container where some ‘problem’ is generated. For example, we leave them without nutrients or we give them a lot of light. By defending themselves, microalgae produce oils, vitamins, antioxidants, dyes, and various other compounds. For example, beta-carotenes are molecules of high interest for the cosmetic and pharmaceutical industry ”, pointed out Gori.

Nutritive effluents

Gori's research group is working on two bioremediation projects: one on effluents from a dairy farm and the other on the liquid part of urban solid waste (that is, the juice that drips from garbage bags), both in the town of Lincoln, in the province of Buenos Aires. By working with effluents, the researchers stopped spending on salts to cultivate microalgae to using polluted waters, rich in nitrogen and phosphorus, as a culture medium.

“When comparing the chemical analyzes of the waters already bioremediated with the standards of the Argentine Food Code, we verify that, in the measured parameters, they are drinkable. However, they are not suitable for human consumption because they come from decomposing faecal matter or garbage, and there is always the possibility that some pathogenic microorganism 'escapes'. In any case, the water can be perfectly used to clean the dairy facilities or for irrigation, instead of using well water, which is drinkable for people and animals ”, Juan told SLT.

Each microalgae gets its photobioreactor

Juan Gori and his team study microalgae at various scales, and explained it to Sobre La Tierra: “At the laboratory scale, we use test tubes, 1 to 2-liter containers and 5 to 120-liter trays. The photobioreactor that we build at FAUBA contains 70 liters. It is a tube 3 meters high by 30 cm wide, located on the terrace of the chair. Although we use it for research, it also helps us to produce microalgae inoculum for bioremediation, and we could easily produce up to 200 grams of dry biomass per harvest. On the other hand, in our projects in Lincoln we are already operating on a pilot scale, with pools of between 1500 and 2000 liters ”.

The technologies to be used vary according to the volume, the available space and the physical place where they will be applied. Certain companies or industries, such as those located near the Riachuelo, for example, could not build pools because they require a lot of surface. In those cases, photobioreactors are ideal because they can be adjusted to the available space, from patios to roofs of buildings.

“At present we are building a new system, still a bit expensive and in an experimental phase. It is based on the use of what we call ‘encapsulates’ which are like tiny photobioreactors shaped like ‘balls’. Inside, by chemical methods, we associate microalgae with bacteria that promote plant growth. We place these mini-photobioreactors in filters, always exposed to sunlight so that photosynthesis takes place. The contaminated water enters the system where the filters are, flows continuously and leaves decontaminated at the other end. In this way we save the cost of separating the water from the microalgae, which is quite expensive. We are designing it to allow us to obtain, in addition to the products already mentioned, new ones such as bioinoculants or biofertilizers ”, the researcher advanced.

Photo: View of a kind of microalgae under the magnifying glass. The Faculty of Agronomy of the UBA has investigated these single-celled plants since 2008. Their cultivation can create a cycle of sustainability for the production of energy and high-value products, linked to the remediation of environmental liabilities.

On earth

Video: Understanding micro-algae (September 2021).