Development of agricultural bioproducts biofertilizers, biostimulants and biopesticides from piggery wastewater treatment-based microalgae

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Nannochloropsis oceanica harvested using electrocoagulation with alternative electrodes: an innovative approach on potential biomass applications

Publication . Figueiredo, Daniel; Ferreira, Alice; Quelhas, P.; Schulze, Peter; Gouveia, Luisa

ABSTRACT: Electrocoagulation is a promising technology to harvest microalgal biomass. However, the commonly used aluminum electrodes release undesired salts that decrease biomass value. In this study, alternative iron, zinc, and magnesium electrodes and operational parameters pH, time and current density were studied to harvest Nannochloropsis oceanica. For recovery efficiency and concentration factor the initial pH was most important using iron electrodes, while time and current density were more relevant using zinc and magnesium electrodes. Optimal parameters resulted in biomass recovery efficiencies > 95%, biomass was concentrated 2.8-7.2 times and contained 15.7-29.1% ashes. Elemental analysis revealed metal salts in harvested biomass resulting from electrode corrosion. Finally, ash contents could be reduced by 65% using EDTA as a chelating agent. The electrocoagulation harvested microalgal biomass enriched in essential metals may be a promising bioresource for agricultural growth inducers, or functional ingredients for feed.

2022-01Journal article

Open access

Biostimulant potential of Scenedesmus obliquus grown in brewery wastewater

Publication . Navarro-Lopez, Elvira; Ruiz-Nieto, Angela; Ferreira, Alice; Acien, Gabriel; Gouveia, Luisa

ABSTRACT: Microalgae are microorganisms with the capacity to contribute to the sustainable and healthy food production, in addition to wastewater treatment. The subject of this work was to determine the potential of Scenedesmus obliquus microalga grown in brewery wastewater to act as a plant biostimulant. The germination index of watercress seeds, as well as the auxin-like activity in mung bean and cucumber, and in the cytokinin-like activity in cucumber bioassays were used to evaluate the biostimulant potential. Several biomass processes were studied, such as centrifugation, ultrasonication and enzymatic hydrolysis, as well as the final concentration of microalgal extracts to determine their influence in the biostimulant activity of the Scenedesmus biomass. The results showed an increase of 40% on the germination index when using the biomass at 0.1 g/L, without any pre-treatment. For auxin-like activity, the best results (up to 60% with respect to control) were obtained at 0.5 g/L of biomass extract, after a combination of cell disruption, enzymatic hydrolysis and centrifugation. For cytokinin-like activity, the best results (up to 187.5% with respect to control) were achieved without cell disruption, after enzymatic hydrolysis and centrifugation at a biomass extract concentration of 2 g/L.

2020Journal article

Open access

Biostimulant and biopesticide potential of microalgae growing in piggery wastewater

Publication . Ferreira, Alice; Melkonyan, Lusine; Carapinha, Sofia; Ribeiro, Belina; Figueiredo, Daniel; Avetisova, Gayane; Gouveia, Luisa

ABSTRACT: Pig farming generates highly polluting wastewaters which entail serious environmental issues when not adequately managed. Microalgae systems can be promising for cost, energy and environment-efficient treatment of piggery wastewater (PWW). Aside from clean water, the produced biomass can be used as biostimulants and biopesticides contributing to a more sustainable agriculture. Three microalgae (Tetradesmus obliquus, Chlorella protothecoides, Chlorella vulgaris) and one cyanobacterium (Synechocystis sp.) were selected after a preliminary screening in diluted wastewater (1:20) to treat PWW. The nutrient removals were 62-79% for COD (chemical oxygen demand), 84-92% for TKN (total Kjeldahl nitrogen), 79-92% for NH4+ and over 96% for PO43−. T. obliquus and C. protothecoides were the most efficient ones. After treating PWW, the produced biomass, at 0.5 g L−1, was assessed as a biostimulant for seed germination, root/shoot growth, and pigment content for tomato, watercress, cucumber, soybean, wheat, and barley seeds. We observed an overall increase on germination index (GI) of microalgae-treated seeds, owing to the development of longer roots, especially in T. obliquus and C. vulgaris treatments. The microalgae treatments were especially effective in cucumber seeds (75-138% GI increase). The biopesticide activity against Fusarium oxysporum was also evaluated at 1, 2.5 and 5 g L−1 of microalgae culture. Except for Synechocystis sp., all the microalgae tested inhibited the fungus growth, with T. obliquus and C. vulgaris achieving inhibitions above 40% for all concentrations.

2021-07Journal article

Open access

Green approach for the valorization of microalgae Tetradesmus obliquus

Publication . Gouveia, Luisa; Jazic, Jelena Molnar; Ferreira, Alice; Maletic, Snezana; Cvetkovic, Dragoljub; Vidovic, Senka; Vladic, Jelena

ABSTRACT: The main goal of this study was to develop an efficient, green approach for the valorization of Tetradesmus obliquus biomass, with zero waste. This microalga was selected because it is widespread, resistant, easy for cultivation, and fast-growing. In the first step, supercritical carbon dioxide (ScCO2) extraction followed by rapid gas decompression was used for the extraction of biomass. The following step was to apply ultrasound-assisted (UA), microwave-assisted (MA), and subcritical water (SW) extraction on the ScCO2-treated biomass to determine the most efficient processing technology. SW demonstrated to be a superior technique over MW and UA with regard to extraction yield and antioxidant content. Moreover, the chemical and microbiological profiles of SW extracts were determined to evaluate their potential and safety. In addition, to create a procedure with zero waste, the solid waste after SW extraction (residue) was analyzed. The organic profile of extracts and residues contained compounds that belong to groups of aliphatic saturated hydrocarbons, aliphatic unsaturated hydrocarbons, alkylated hydrocarbons, ketones, phenols, and esters. Furthermore, these compounds can be applied in different industries including the pharmaceutical and cosmetic industries. Additionally, the content of metals in residues indicated that this material can be used as animal feed and in agriculture. Finally, a complete reduction of microorganisms present in the initial biomass was obtained for the extracts and residues, indicating their safety.

2021-12Journal article

Open access

Future perspectives of microalgae in the food industry

Publication . Ferreira, Alice; Guerra, Inês; Costa, Margarida; Silva, Joana; Gouveia, Luisa

ABSTRACT: Microalgae have been consumed by humans for thousands of years. Research has shown that microalgae exhibit huge potential to meet the dietary needs of the growing population, generating great interest in these organisms. Thanks to their nutritional composition, mainly their high protein content, but also to the presence of bioactive compounds with functional properties that provide added health benefits, microalgae hold major opportunities for innovative and sustainable product development within the food industry. Furthermore, they possess compounds with stimulant properties that can be used to enhance agricultural yields, while providing an environmental benefit to sustainable agriculture. However, current microalgae exploitation for the food industry still presents some drawbacks, mainly because of the underdeveloped technologies and processes currently available for microalgae cultivation and processing. This chapter describes the use of microalgae as an ingredient in innovative food products with potential health benefits. It displays the research work done in a wide range of food products with incorporated microalgae, as well as some marketed microalgae-based food products commercially available today. Finally, the most promising future trends in microalgae food applications are highlighted.

2021-05Book part

Open access