Effect of the Foliar Application of Microalgae Hydrolysate (Arthrospira platensis) and Silicon on the Growth of Pelargonium hortorum L.H. Bailey under Salinity Conditions

Plant growth is limited by salinity stress. There are few strategies for alleviating it although Arthrospira platensis and silicon can stimulate plants to grow under stress conditions. The aim of this work was to study the effects of both a single and a joint application of Arthrospira platensis and silicon on the growth of Pelargonium hortorum L.H. Bailey under salt stress conditions. Plants were exposed to 2.0, 3.0, and 3.5 dS m−1 EC (electrical conductivity), with and without the application of microalgae and silicon. At the end of the trial, the biometric parameters and the plant analysis were determined. The microalgae hydrolysate concentration was 5 g L−1 and the silicon concentration was 150 mg L−1. Foliar spraying was applied weekly. Pelargonium can be grown in moderately saline irrigation water (3.0 dS m−1). This bedding plant mitigates salt stress by avoiding the uptake of Cl− ions and by tolerating a high Na+ concentration in the tissue. The joint foliar application of Arthrospira microalgae and silicon stimulates root, shoot, leaf, and flower formation in the Pelargonium hortorum L.H. Bailey crop under salinity conditions (3.5 dS m−1)

Optimisation of Protein Recovery from Arthrospira platensis by Ultrasound-Assisted Isoelectric Solubilisation/Precipitation

A response surface methodology was used to optimise the solubilisation and precipitation of proteins from the cyanobacterium Arthrospira platensis. Two separate experiments were designed and conducted in a sequential manner. Protein solubilisation was affected by pH, extraction time, and biomass to solvent ratio (p < 0.001). Although spray-drying and the osmotic shock suffered when resuspending the dried biomass into distilled water led to a certain degree of cell wall disruption, the amount of protein that could be solubilised without an additional disruption step was in the range 30–60%. Sequential extractions improved protein solubilisation by less than 5%. For this reason, a pre-treatment based on sonication (400 W, 24 kHz, 2 min) had to be used, allowing the solubilisation of 96.2% of total proteins. Protein precipitation was affected by both pH and extraction time (p < 0.001). The optimised precipitation conditions, which were pH 3.89 over 45 min, led to a protein recovery of 75.2%. The protein content of the extract was close to 80%, which could be further increased by using different purification steps. The proteins extracted could be used in the food industry as technofunctional ingredients or as a source of bioactive hydrolysates and peptides for functional foods and nutraceuticals

Annual production of microalgae in wastewater using pilot-scale thin-layer cascade photobioreactors

Microalgae based wastewater treatment has been suggested as an alternative to polluting and energy-consuming conventional processes. The main advantage of this strategy is the dual role of microalgae: they recover nutrients from waste and simultaneously produce biomass with varied industrial applications. In the current study, biomass of Scenedesmus sp. was produced using primary wastewater in two pilot-scale thin-layer cascade photobioreactors (63 and 126 m2). The wastewater used for microalgal growth was not subjected to any conventional treatment process, besides removal of solids, and contained a variable N-NH4+ content of 83.0-210.6 mg·L-1. Biomass productivity values were comparable to those obtained when operating using freshwater and commercial chemicals as nutrient sources. When operating at a dilution rate of 0.3 day-1, the average annual productivity was 24.8 g·m-2·day-1 (82.0 t·ha-2·year1) with a maximum of 32.8 g·m-2·day-1 in summer. Inorganic nitrogen and phosphorus removal rates varied between 695.4-2383.4 and 70.4-111.8 mg·m-2·day-1 respectively. Production of Scenedesmus sp. using wastewater would allow not only to process large volumes of water that could be reused for agricultural irrigation or safely disposed into water streams, but also reduce production costs by 0.44 €·kg-1, based on a preliminary economic analysis. Overall, results demonstrate that thin-layer cascade reactors can be used to effectively remove nutrients from wastewater while simultaneously produce valuable biomass with potential applications in agriculture or animal feed production

Year-long production of Scenedesmus almeriensis in pilot-scale raceway and thin-layer cascade photobioreactors

Biomass of Scenedesmus almeriensis was produced outdoors for 12 months using three different photobioreactor designs. Optimum dilution rates to achieve the highest biomass productivities were 0.2 day-1 for raceways and 0.3 day-1 for thin-layer reactors. Biomass productivities achieved using thin-layer cascade photobioreactors during the months of higher photosynthetic activity reached 30-35 g/m2·day, higher than those obtained using raceways during the same period: 20-25 g/m2·day. Photosynthetic efficiency was lower in spring/summer when compared to autumn/winter, suggesting that a larger share of the solar energy that reaches the culture in spring/summer is not used for microalgal growth. During summer, culture temperature reached 40 °C in thin-layer photobioreactors, which demonstrates the importance of selecting microalgal strains able to resist these conditions. Photoinhibition was not observed at incident irradiances up to 1600 μE/m2·s. However, dissolved oxygen values were especially high in thin-layer photobioreactors during this time of the year. They reached maximum values of 400% and showed an inhibitory effect on microalgal growth

Polvo insoluble de pulpa de coco (Acrocomia aculeata) como biocatalizador

El fruto de Acrocomia aculeata (coco) se usa para obtener aceites que puedan extraerse de la pulpa y almendra. La extracción del aceite de pulpa es un proceso que se realiza por prensado quedando restos que finalmente se desechan. El objetivo de este trabajo fue evaluar las propiedades biocatalíticas y fisicoquímicas del desecho de la pulpa de coco para aplicarlo bajo condiciones solida e insoluble como biocatalizador heterogéneo. Para ello se obtuvo un polvo insoluble de pulpa de coco siguiendo un proceso de obtención no convencional. Se determinó las propiedades fisicoquímicas mediante métodos estandarizados de análisis y se evaluó la actividad lipasa “per se” de este polvo insoluble comparándolo con la actividad de lipasas inmovilizadas comerciales en la reacción de hidrolisis de una emulsión (O/W) 0,5% de Tween 80 (polioxietileno sorbitan monooleato). Paralelamente se evaluó la actividad lipasa de la pulpa de coco en forma de extracto soluble. Como resultado se observó que el polvo de pulpa de coco obtenido por el método no convencional presento menor contenido de humedad y de acidez que el obtenido por el método tradicional. El polvo de pulpa de coco obtenido y tratado con alcoholes con grado decreciente de polaridad resulto ser biocatalítico “per se” obteniéndose actividad comparable con las lipasas comerciales evaluadas. La actividad en los extractos crudos solubles fue menor a la del polvo insoluble de pulpa. La actividad biocatalítica “per se” del polvo de pulpa de coco podría aplicarse a procesos biocatalíticos para reducir costos y en sistemas no convencionales.CONACYT - Consejo Nacional de Ciencia y TecnologíaPROCIENCI

Processing Nannochloropsis gaditana biomass for the extraction of high value biocompounds

Extraction of carotenoids and fatty acids from microalgae is a technological bottleneck in processing. An improved extraction process was developed to scale the production of these bioproducts from Nannochloropsis gaditana. Different cell disruption methods were evaluated in terms of carotenoid release. Ethanol was substituted with isopropyl alcohol in a three-component solution of water:isopropyl alcohol:hexane (WIH), in which the extracts were separated by solution partitioning. This resulted in higher carotenoid and fatty acid recovery yields if compared with the standard method. The extraction method was replicated on a pilot scale, obtaining similar carotenoid recovery yields, higher than those of the standard method. Although fatty acid recovery was lower than that of the small-scale tests, yields above 85% were obtained. This demonstrated that the method was scalable for the extraction of high-value products from microalgae up to 10-L reactor volume. The use of isopropyl alcohol, which is cheaper than ethanol, and the separation of the solution phases by partitioning (avoiding drying) could contribute to reduce operation costs of downstream processing

Year-long evaluation of microalgae production in wastewater using pilot-scale raceway photobioreactors: Assessment of biomass productivity and nutrient recovery capacity

The production of Scenedesmus sp. using wastewater was validated with pilot-scale raceway photobioreactors during a complete annual cycle in Almería (Spain). Three different dilution rates (0.1, 0.2, or 0.3 day-1) were evaluated. Biomass productivity was significantly affected by season (temperature and solar radiation) achieving a maximum value of 25.1 g·m-2·day-1 when operating at a dilution rate of 0.2 day-1 in summer. Up to 96% of the N-NH4+ present in the media was either assimilated by microalgae to produce biomass, converted to N-NO3+ by the action of nitrifying bacteria, or desorbed (stripping). Maximum nitrogen removal rates reached 4286.6 mg·m-2·day-1 in summer. In terms of P-PO43+, up to 75% was removed, with removal rates ranging from 147.5 mg·m-2·day-1 in winter to 227.2 mg·m-2·day-1 in summer. Data reported herein was used to validate the ABACO model, which demonstrated to be robust enough to accurately predict biomass productivity in pilot-scale outdoor open raceways throughout the year (R2=0.929; 0.05). The current study demonstrates the potential of raceway reactors and Scenedesmus sp. to recover nutrients from unprocessed wastewater with an exceptionally high content of N-NH4+ at pre-industrial scale. Keywords: Bioremediation, microalgae, biomass, photobioreacto

Improvement of wastewater treatment capacity using the microalga Scenedesmus sp. and membrane bioreactors

Primary urban wastewater was processed using the microalga Scenedesmus sp. in an outdoor pilot-scale raceway reactor connected to an ultrafiltration membrane. The goal was to separate cellular retention time from hydraulic retention time. This strategy led to a 129.3% increase in the daily volume of wastewater treated per square meter, and to a 48.7% increase in biomass productivity to a final value of 22.2 ± 1.9 g·m-2·day-1. Nutrient removal was highly influenced by permeate rate, allowing to remove up to 0.65 mg·m-2·day-1 of phosphates. Over 99% of ammonia was removed when the ultrafiltration membrane was used, although this was partially due to nitrate production by nitrifying bacteria: higher permeate rates led to higher relative abundance of the nitrifying bacterial. The amplification and sequencing of the microalgae-bacteria samples led to the detection of ammonia-oxidizing bacteria and nitrite-oxidizing bacteria, such as Bradyrhizobiaceae, Nitrospiraceae, Nitrosomonadaceae, and Chromatiaceae. The most abundant families detected in the microalgae-bacteria biomass were Rhodobacteraceae and Comamonadaceae

Consumer knowledge and attitudes towards microalgae as food: The case of Spain

Spanish consumers’ knowledge and attitudes towards microalgae as food were assessed using a specific questionnaire - a total of 3,084 Spanish consumers over 18 years old were considered in the current study. Overall, the questionnaire revealed that there is a huge lack of knowledge on basic aspects of microalgae, especially within the youngest respondents (18-24 years old) and for those aged over 65 years old. Approximately 85% of all respondents scored the statement “There is a big lack of information about microalgae” with either 4 or 5 (using a 5-point hedonic scale), demonstrating that microalgae and their potential applications are unknown to the majority of the Spanish population. Spanish consumers consider microalgae as: (i) sustainable and environmentally friendly, (ii) nutritious and healthy, and (iii) safe, which is of key importance for food products. The main reasons that were given for not consuming microalgae were lack of information available on the product and lack of consuming habit. The current study also demonstrated that increasing consumer’s knowledge on microalgae has the potential to increase consumer choice and market shares of microalgae-enriched products. Results reported herein could be extrapolated to other European countries, although perception and attitudes towards food can vary depending on cultural considerations