Researchers of the University of Almería develop fertilizers with microalgae grown in wastewater from the beer industry. The results show a 40 percent growth boost in cucumber, green soybean or watercress crops.

The work has been carried out by a research team from the Department of Chemical Engineering of the University of Almería (UAL), in collaboration with the Institute for Agricultural and Fisheries Research and Training (IFAPA), and the National Laboratory of Energy and Geology (LNEG ) of Portugal, according to the Discover Foundation.

Specifically, the application of the biomass of this microorganism in a concentration of 0.1 grams per liter Has got increase seed germination watercress by 40 percent, compared to the development of these crops if no fertilizer is added.

Microalgae raised in waste from the beer industry

The results have also been positive in that this microalgae enhances an essential hormone in stem growth, as is the so-called gibberellin, and another that is mainly involved in the development of the root of the plant, auxin.

In relation to the latter, the best results have been obtained, with up to 60 percent increase in root development, applying a Scenedesmus obliquus microalgae biomass in a concentration of 0.5 grams per liter.

In this case, UAL researchers have previously applied a method that breaks the cell wall of the microalgae and thus release all its contents into the medium, to then put the extracts obtained in contact with the seeds that are used as models to carry out the bioassays.

The research entitled ‘Biostimulant Potential of Scenedesmus obliquus Grown in Brewery Wastewater’ has been published in the scientific journal Molecules. Its main objective is that agriculture has more biological products with which to reduce or eliminate the use of industrial fertilizers in agricultural crops.

Biomass obtained with microalgae cultivated in residues of the beer industry.

From microalgae to cultivation

The first step, once the Scenedesmus obliquus microalgae has been cultivated, is harvest biomass –The part that will be of interest for the development of the experiment– in order to concentrate it using a centrifugation to remove residual water. From this process a biomass paste arises on which various treatments are applied to see how it affects the growth of plants.

Among other issues, this research team has analyzed whether or not it is necessary to break the cells of this paste in order to use it as a fertilizer. “The substances that interest us are found inside cells. Depending on the type of microalgae that we are going to use, the cell wall can be more or less difficult to break, ”he says to the Discover Elvira Navarro Foundation, a researcher at the UAL who has participated in the trials.

The processes that apply to each species depend on its structure. “There will be species with a very thin cell wall that do not require any special treatment to break, and others with a thicker one in which it will be necessary to previously break the cells to obtain the substances of interest,” he clarifies.

Stimulating proteins

This Andalusian scientific team has also analyzed the effect of apply enzymatic hydrolysis to the Scenedesums obliquus. It is a procedure that breaks down proteins to release amino acids into the medium, which are chemical compounds directly related to the growth of plants.

The objective, as in the other trials, has been check if the microalgae promote the growth of these seeds compared to seed development if no fertilizer is added.

The results of these works have also been positive, and have once again demonstrated the potential that this microalgae has for the growth of the plant. Thus, they have advanced in what has been achieved in previous investigations of this and other groups, proving that they are microorganisms with the ability to contribute to the production of sustainable and healthy food, in addition to wastewater treatment.

For the future, the work involves improving the treatments and thus obtaining a generalized process that is also useful for other species, as well as the cultivation conditions or the subsequent storage of the final product. “It is also about increasing knowledge about the observed bioactivity and relating the results with the different substances involved in plant growth,” explains Navarro.

This research, included within the European project SABANA (initials of its name in English, ‘Sustainable Algae Biorefinery for Aquaculture and Agriculture’), has been carried out in the last three years at the UAL and the facilities that IFAPA has in La Cañada from San Urbano (Almería), and is financed by various European projects such as the Sabana and the Green Biorefinery, being the result of a collaboration of UAL staff with researchers from the LNEG in Lisbon (Portugal).

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