- ArtículoAcceso AbiertoThree-Dimensional Reconstruction of Halamphora coffeaeformis Frustule from Scanning Electron Micrographs(2020)The diatom Halamphora coffeaeformis represents an alternative feedstock of oils for the biodiesel production. In addition, its siliceous cell wall (named frustule) presents possible industrial applications that have not been reported in the literature yet. Thus, the main objective of this study was to perform a three-dimensional reconstruction of H. coffeaeformis´ frustule from scanning electron micrographs, in order to have a study model. For this, the biomass of the species growing in a photobioreactor was harvested and treated as follows: a) some samples were dehydrated and subjected to a critical point; and b) other samples were treated with H2O2 in order to analyse the frustule´s ornamental pattern. All samples were metallized with gold, using an Argon plasma metal evaporator (Pelco model3) and they were observed with a LEO Scanning Electron Microscope, model EVO 40 XVP 2004. The frustules were elliptical to lanceolate with protracted ends. Valves presented convex dorsal margin and straight ventral margin. Dorsal striae were biseriate and radiate; ventral striae were short, uniseriate, radiate at the center and convergent at the ends of the valves. The raphe was straight and close to the ventral margin. The micrographs were analysed and separated into layers with the Adobe Photoshop CS6 software. The layers were vectorised with the Inkscape software and loaded and assembled in the Tinkercad software. The final aspects of the digital model were moulded on the page https://stephaneginier.com/sculptgl/. Finally, 3D printing was done with a CoLiDoTM 3.0 L printer, obtaining a three-dimensional replica representative of the H. coffeaeformis´ morphology . This replica will serve as a model for studies of its frustules related to nanotechnology and /or catalyst support applications.
- ArtículoAcceso AbiertoA practical tool for selecting microalgal species for biodiesel production(2020)In the search for energy sources to replace fossil fuels, microalgae have shown promising characteristics. Their cultures have several advantages over the conventional crops used for commercial biodiesel: they have fast growth rates and a high lipid content and can grow in environments unfit for agriculture. However, relatively few species have so far been studied as biodiesel feedstock. In order to facilitate the search for potentially useful species/strains, in this work, a bioprospecting tool based on biomass and oil production process requirements, triacylglyceride content, and biodiesel properties has been developed. For this purpose, an overall score (OS) was proposed as a tool based on biological, economic, and environmental factors. By applying the OS to nine species, we were able to narrow down the number of species within the diatom group, which are potentially suitable for large-scale biodiesel production. Halamphora coffeaeformis, Navicula cincta, and N. gregaria were the species with the highest OS (1.65-1.5). It is expected that this tool will provide a useful contribution to the criteria applied in the selection of microalgal species for large-scale biodiesel production.
- ArtículoAcceso AbiertoEnhancement of polyunsaturated fatty acid production under low-temperature stress in Cylindrotheca closterium(2020)Marine microalgae synthetize great amounts of essential metabolites such as fatty acids and amino acids. In addition, their exposure to stress factors can induce the overproduction of these desirable metabolites. Thus, in this work, we assessed the effect of low-temperature stress on lipid production and composition of the diatom Cylindrotheca closterium, in order to evaluate its potential as an alternative feedstock of essential polyunsaturated fatty acids (PUFAs). The alga was first cultured in a photobioreactor at 20 °C (control), and stressed by suddenly lowering the culture temperature, from 20 °C to 11 °C, at the exponential (LTEP) or stationary (LTSP) growth phases. Neutral lipids (NLs) were the main lipid fraction of all conditions assayed, and their production was maximal at LTSP. Fatty acid analysis also showed that the greatest production of PUFAs was observed in the NL fraction at LTSP condition. In terms of essential fatty acids, the production of the omega-3 fatty acids eicosapentaenoic acid and docosahexaenoic acid was similar in both treatments. The production of omega-6 fatty acids was significantly higher in the LTSP condition due to an increase in arachidonic acid content. Sterols increased under both stress conditions, with a predominance of cholesterol. Considering that the LTSP condition elicited the best PUFA production, the amino acid composition was determined. The 46.81% of total amino acids were essential components for aquatic animals. These findings provide evidence of the potential of C. closterium as an alternative, sustainable source of sterols, essential fatty acids, and amino acids.
- ArtículoAcceso AbiertoBiodiesel production from Halamphora coffeaeformis microalga oil by supercritical ethanol transesterificati(2019)The marine benthic diatom Halamphora coffeaeformis is a potential feedstock for biodiesel production. This species shows high growth rates, important triacylglycerol (TAG) contents and grows in seawater making largescale cultivation advantageous. Moreover, sustainable biofuel production in future biorefineries requires the implementation of technologies that employ renewable solvents. Thus, the goal of this work was to evaluate ethanol usage as extraction solvent and reaction medium for biodiesel production from H. coffeaeformis. In a first step a bio-oil extraction was carried out comparing ethanol and n-hexane to investigate the performance of ethanol with respect to a conventional solvent. Then, a free-catalyst supercritical ethanol transesterification of the bio-oils was carried out to obtain biodiesel. Higher lipid extraction yields were obtained using ethanol respect to n-hexane (26 wt.% vs 21.1 wt.%). The transesterification of crude lipids extracted with ethanol as solvent at 305 °C and 40 min. produced up to 15.9 wt.% of biodiesel respect to dried biomass processed. Comparable biodiesel yields were obtained using non-renewable organic solvents and a conventional catalytic technology. Thus, ethanol extraction and subsequent supercritical transesterification of H. coffeaeformis oil proved to be technically feasible and environmental friendly technology for the production of biodiesel.
- ArtículoAcceso AbiertoAssessment of Halamphora coffeaeformis Growth and Biochemical Composition for Aquaculture Purposes(2020)The vast majority of the world’s fishery by-products are utilized in the fish farming industry. However, due to the high cost and unsustainability of these by-products, alternative sources must be found. Marine diatoms produce important amounts of fatty acids, sterols, proteins and carbohydrates. In this work, we assessed the nutritional value of Halamphora coffeaeformis at the exponential growth phase, to determine its suitability for aquafeed. The strain was grown in a photobioreactor at 20 ◦C for 6 days. The production of proteins, lipids and carbohydrates was determined, and essential fatty acid, sterol and amino acid composition was assessed. The highest values of triacylglycerides (TAG), free and esterified sterols, proteins and carbohydrates were found after 6 days of growth in the photobioreactor. Fatty acid analysis by gas chromatography showed the presence of eicosapentaenoic (EPA) and arachidonic (ARA) in amounts similar to those for fish oils. In terms of sterols, a predominance of stigmasterol was observed, followed by cholesterol. The amino acid composition revealed 50% of them to be among those essential for fish and other aquatic animals. Finally, a suitable amount of carbohydrates was found in H. coffeaeformis cultures. Together, these findings support the use of H. coffeaeformis as an alternative and sustainable source for aquafeed to partially replace the use of fishery by-products.