Microalgae have commercial potential in different sectors of the industry. Specifically in modern agriculture, they can be used because they have the ability to supply nutrients to the soil and produce plant growth hormones, polysaccharides, antimicrobial compounds, and other metabolites that improve agricultural productivity. Therefore, products formulated from microalgae as biofertilizers and biostimulants turn out to be beneficial for agriculture and are positioned as a novel and environmentally friendly strategy. However, these bioproducts present challenges in preparation that affect their shelf life due to the rapid degradation of bioformulated products. Therefore, this work aimed to provide a comprehensive review of biofertilizers and biostimulants from microalgae, for which a bibliometric analysis was carried out to establish trends using scientometric indicators, technological advances were identified in terms of formulation methods, and the global market for these bioproducts was analyzed.

Berry fruits are an important dietary source of health-promoting antioxidant polyphenols. Interestingly, berry leaves of diverse species, including strawberries, have shown higher bioactive phytochemical content in the leaves than in the fruit. Moreover, the vegetative part of the plants is usually discarded, representing a presumably large source of underutilized bioactive biomass. In this investigation, the polyphenol profiles of tropical highland strawberry (Fragaria x ananassa cv. Festival) leaves and fruits were compared by high-performance liquid chromatography coupled with a diode array detector (UHPLC-DAD) and mass spectrometry (HPLC-MS). The total polyphenol strawberry leaf extracts exhibited a 122-fold-higher total polyphenol content and 13-fold higher antioxidant activity (ORAC) than strawberry fruits, and they showed evidence of possible photoprotective effects against UV damage in human melanoma cells (SK-MEL-28) and in murine embryo fibroblasts (NIH/3T3), together with promising anti-proliferative activities against the same melanoma cells. Seven polyphenols were confirmed by HPLC-DAD in the leaf extracts, with differences depending on fraction solubility. Moreover, three substituted quercetin derivatives, three substituted kaempferol derivatives, two anthocyanins, and catechin were confirmed in the soluble fraction by HPLC-MS. Given their higher total polyphenol content and bioactive activities, underutilized strawberry Festival leaves are a potential source of apparently abundant biomass with prospective bioactive applications.

Meso- and extremophilic microalgae and cyanobacteria have a wide range of biotechnological applications. However, the industrial demand for bioactive molecules and the redundancy of these molecules has resulted in a need for new methodologies for enhanced production and the discovery of specialized metabolites. Co-cultivation has been established as a promising approach to addressing these challenges. In this context, this work aimed to describe the state of the art of the co-cultivation method involving meso- and extremophilic photosynthetic microorganisms, as well as discuss the advantages, challenges, and limitations of this approach. Co-culture is defined as an ecology-driven method in which various symbiotic interactions involving cyanobacteria and microalgae can be used to explore new compounds and enhanced production. Promising results regarding new bioactive metabolite expression and increased production through co-cultivation-based research support that idea. Also, the metabolic diversity and evolutionary adaptations of photosynthetic microorganisms to thrive in extreme environments could improve the efficiency of co-cultivation by allowing the implementation of these microorganisms. However, the complexity of ecological interactions and lack of standardization for co-cultivation protocols are obstacles to its success and scientific validation. Further research in symbiotic interplays using -omics and genetic engineering, and predictive experimental designs for co-cultures are needed to overcome these limitations.

The animal feed industry is continuously researching new feed additives to substitute other materials, reduce costs, or add value to the final product. The microalgae Arthrospira maxima, cultivated using wastewater as a nutritional source, was evaluated as a feed additive by including 2, 4, and 6% in isocaloric and isoprotein diets for laying hens. Five replicates per treatment with 5 hens per cage were used during an experimental period of 28 days. Productive behavior and egg characteristics (quality, fatty acid profile, cholesterol level) were evaluated. The inclusion of microalgae up to 4% in diets for 52-week-old laying hens did not affect productive performance (egg production, egg weight, egg mass, FCR, shell thickness, and Haugh units). No effects were observed on the cholesterol level or the concentration of fatty acids in the eggs, but more information is needed to determine if the microalgae drying or storage process can generate variations of these results. The inclusion of 6% microalgae produced an acceptable egg yolk color for the local market. The results indicate that this material can be used as a protein source up to an inclusion of 4% in the diet, and hens may need an adaptation period to maintain production at the 6% inclusion level.

Microalgae are promising as prebiotics in aquaculture. Arthrospira maxima has potential nutritional value but is poorly studied. We assessed A. maxima feed supplementation in tilapia fry and evaluated its effect on growth performance and gut microbiota. Fish were cultivated in ponds under 0%, 5%, 10%, and 15% A. maxima inclusion treatments. Growth parameters and biomass proximate analysis were assessed. A meta-amplicon analysis was performed on the gut microbiota using DADA2 and PICRUST2 for functional prediction. Among treatments, the 5% supplementation group seemed to present no negative effect on growth parameters and did not compromise the nutritional quality of tilapia fry biomass. Microbial composition was characterized by Cetobacterium, Pseudomonas and Aeromonas genera, and a predominance of beneficial metabolic pathways. Microbiota of tilapia fry fed with A. maxima showed unique genera with reported beneficial functions in tilapia. The abundance of potential pathogenic taxa was significantly decreased in supplementation treatments, possibly related to valuable compounds of A. maxima. The inclusion of the microalgae supported the stability of the microbiota, favoring the growth of commensal species. This seems to have an effect on decreasing the presence of pathogenic genera in the gastrointestinal tract. Overall, our work proposes 5% feed inclusion of A. maxima to be the most suitable for tilapia fry aquaculture to maintain production rates while improving general health.

La microalga Isochrysis galbana es un bioproducto alimenticio fundamental en los cultivos acuícolas, ya que aporta calidad nutricional a las larvas en su desarrollo óptimo. El desarrollo de la acuicultura en Costa Rica ha generado la necesidad de fomentar la producción microalgal para producir mayor cantidad y calidad de biomasa, por lo que se generó un diseño para evaluar la incidencia de factores ambientales en el cultivo de esta microalga. Los cultivos microalgas se llevaron a cabo en botellas con una capacidad de 5,5 L, se realizaron en total 6 tratamientos, tres con longitud de onda de luz blanca (500 nm) y tres con longitud de onda de luz azul (455 nm). En cada longitud de onda se analizaron tres fotoperiodos: a- 16h:8h, b- 12h:12h y 24h (Luz/Oscuridad) y 4 salinidades (32ppm, 30ppm, 28ppm y 25ppm) las cuales se trabajaron por triplicado, para un total de 12 cultivos por tratamiento. Después de 12 días de cultivo se observó una mayor cantidad de células/ml en el tratamiento de luz azul con irradiación constante 24h y salinidad de 28ppm, El fotoperiodo de 12h:12h (L/0) no tuvo en buen crecimiento en ninguna de las longitudes de onda de luz empleadas. En cuanto a la producción de biomasa se determinó que la luz azul, con fotoperiodo 16h:8h (L/O) y salinidad de 30ppm fue el que produjo mayor biomasa seca. Se pudo determinar que la combinación de factores de luz azul, con luz constante de 24h y salinidad de 28ppm, permitieron alcanzar la mayor densidad celular.