255 research outputs found
Fatty acid composition and technological quality of the lipids produced by the microalga Scenedesmus dimorphus 1237 as a function of culturing conditions
Scendesmus dimorphus is an oleaginous eukaryotic microalga, able to produce and accumulate lipids up to a
weight fraction of 49%. Aim of the present work is investigating the production of lipids by S. dimorphus 1237
and characterize them at a fatty-acid level. The variables accounted for were: the nutrient supply level and the
extraction system (Soxhlet and bead beating). Two lipid phases were extracted by sequential, twin-solvent
system (hexane and a chloroform:methanol mixture), the quantified gravimetrically and analyzed for their
individual fatty acid composition by gas chromatography. The maximal total lipid concentration was measured
by Soxhlet extraction in deficient nitrogen conditions (0.88 mg/L) and was found to be 49% (dw). In particular,
palmitic acid was increased from 15% to 58% under phosphorous starvation and oleic acid content was
increased from 8% to 40% under nitrogen starvation. Finally palmitic, palmitoleic and linolenic acid
represented together more than 70% of the extracted lipids
Production of the freshwater microalgae Scenedesmus dimorphus and Arthrospira platensis by using cattle digestate
Microalgae are considered one of the most promising feedstocks for biofuels; these microorganisms are also able to enhance the nutritional content of conventional food preparations, or can be converted into other fuel products, such as hydrogen, ethanol, long-chain hydrocarbons resembling crude oil, or biogas.
Scendesmus dimorphus 1237 is an oleaginous eukaryotic microalga, able to produce and accumulate lipids up to a fraction around 43%. In condition of nitrogen starvation this percent grow sup to 50% of dry weight. Therefore this microalga is considered a promising feedstocks for biofuels. Arthrospira platensis is a cyanobacterium with a considerable potential as a source of high biologic value proteins (“superfood”), pigments (phycocyanin and beta-carotene) and poly-unsaturated fatty acids (PUFA) which have been shown to have therapeutic effects on humans.
Anaerobic digestion liquid effluents feature the presence of nutrients, such as nitrogen and phosphorous, which makes them interesting for a potential application in microalgal biomass production.
Aim of this work is investigating the use of liquid anaerobic cattle manure digestate for the photosynthetic growth of these microalgae
Mass transfer, light pulsing and hydrodynamic stress effects in photobioreactor development
Photobioreactor scalability involves multiple different interacting aspects including mass transfer, light pulsing
and hydrodynamic stress. An efficient carbon dioxide supply and a frequent displacement of cells from poorly
to highly illuminated zones is desired to maximise the achieveable specific growth rate. However, a strong
mixing is energy consuming and may reduce the specific growth rate because of induced cell damage.
The current work examines mass transfer effects in photobioreactor development and estimates their
relationship to light pulsing and hydrodynamic stress effects with a special reference to the novel inclined, thinlayer,
wavy-bottomed cascading photobioreactor
Description of the biofouling phenomena affecting membranes by the boundary flux concept
Membrane fouling, showing up with a significant reduction of process productivity and membrane lifetime, is one of the main issues in membrane technologies and has been successfully described by the boundary flux concept. Although the concept was applied for both organic and inorganic fouling, biofouling enjoys partial treatises in literature. In this work, a model extending the boundary flux concept to biofouling issues was developed. A population dynamics-based model considering the development of a fouling layer originated by attached growing biomass on the surface of the membrane using nutrients and substrates available in the processed feed has been developed. The manuscript highlights the critical aspects of the developed model and the possible connection points between it and the boundary flux concept
A novel approach for the production of nitrogen doped TiO2 nanoparticles
In this study a visible light active nitrogen doped nanostructure titanium dioxide was synthesized by a simple mixing of Degussa P25 and Urea powder and further thermal treatment under the adequate conditions. Photocatalytic activity of produced nanoparticles was verified by providing of photocatalytic degradation of phenol aqueous solution. Mainly this work was focused on the investigation of the following effects: urea concentration, temperature treatment, catalyst loading and initial phenol concentration. Kinetics study was also carried out. The approach appears to be successful and may be applied for example during the photocatalytic treatment of wastewater streams without or with a limited aid of UV lamps. Copyright © 2015, AIDIC Servizi S.r.l
Extraction and purification of exopolysaccharides from exhausted Arthrospira platensis (Spirulina) culture systems
Microalgal endo and exopolysaccharides (EPS) are attracting increasing interest for their potential applications
in the food, cosmetic and pharmaceutical industries. The standard applications of microbial EPS are as food
coatings, emulsifying and gelling agents, flocculants, hydrating agents etc. They present unique biochemical
properties that make them interesting from the biotechnological point of view. Their physical-chemical
properties are interesting for biomedical applications, since polysaccharides have been demonstrated to
possess inhibitory properties against various types of viruses, bacteria and tumors. The purpose of this work is
to upgrade the exhausted culture media resulting from the cultivation of the cyanobacterium Arthrospira
platensis (Spirulina), in order to extract the exopolysaccharides excreted by the cyanobacterium and test their
exploitation potential in a cosmetic context (a body cream). The study results include: defining the
composition and the productivity of EPS by the Spirulina culture, developing a suitable application method for
the DPPH assay in lipophilic matrices, and evaluation of the antioxidant action of these polymers in the
cosmetic field
Potential of choline chloride - based natural deep eutectic solvents (NaDES) in the extraction of microalgal metabolites
In a typical chemical process, the solvents are widely used for the dissolution of the reagents, to favor the
kinetics and the thermodynamics of a chemical reaction, for the extraction of products, for the separation of
mixtures. However most of the currently used organic solvents are characterized by different properties
harmful to human health and the environment. Among the principles of Green Chemistry are that solvents
should be innocuous to Man and to the Environment (safer solvents) and that the substances used in a
chemical process should be chosen to minimize the potential for chemical accidents (intrinsically safe
processes).
Biorefining, the biomass Era counterpart of oil refining is most likely going to be extraction-based, and thus
heavily solvent-dependent, much as the Oil Era was based on distillation and hence heat-dependent. Ionic
Liquids (ILS) and eutectic mixtures exploited as solvents (DES) are two major classes of solvents that are
making their way in Green Chemistry and, in particular, in biomass processing research.
NaDES ('Natural Deep Eutectic Solvents'), i.e. mixtures formed by natural primary metabolites present in all
organisms, such as sugars, polyols, amino acids, organic acids, derivatives of choline, form intermolecular
hydrogen bonds and, when mixed in a certain ratio, change their state from solid to liquid forming a eutectic
system. The most interesting NaDESs are those in which water is one of a ternary system since the degree of
dilution with water modifies such physical properties of the NaDES as the density, the viscosity, and the
polarity. By modulating the water content the solvation power can be adjusted to specific needs.
In this work, the PCH (1,2-propanediol, choline chloride, water 1:1:1) NaDES was used to treat microalgal
biomass and carry out the extraction of cellular components, such as lipids, proteins, carbohydrates and
photosynthetic pigments (chlorophylls and carotenoids) from the biomass itself.
Three sets of experiments were carried out based on different contact time between biomass and PCH: 24
and 72 hours, with and without pre-treatment with ultrasound. Biomass was shaken together with the PCH
solvent in the presence of glass beads to promote the extraction efficiency. The analysis of the extract
composition was carried out spectrophotometrically for pigments (chlorophylls and carotenoids), with
biochemical assays for proteins and carbohydrates and gravimetrically for the determination of lipids. The
results showed the ability of PCH, coupled with the mechanical destruction of cell walls, to solubilize a wide
range of polar biomolecules at room temperature
Growth of microalgae in spectrum-neutral, volume-distributed light restriction as the baseline of wastewater exploitation
Producing culture media for microalgae from wastewaters may help reduce the culture management and wastewater treatment costs, but concomitant light limitation, nutrient restriction, toxic and growth-promoting effects complicate the preliminary data analysis and their subsequent exploitation. Post-treating the experimental data with a light-centred growth model would warrant the process developer with a powerful tool, but also a difficult one to validate in the absence of an accurate description of the microalgal growth behaviour in a purely radiative (i.e., non toxic) light restriction condition. Furthermore, purely radiative light restriction cannot be obtained by simply adjusting the external irradiance since in this latter case local irradiance and biomass growth cannot be decoupled. Aim of this work is, thus, carrying out an experimental investigation on the influence of purely radiative, chromatically neutral (grey), and volume-distributed light restriction on the observed growth rate of a microalgal culture. Semi-continuous cultures of the microalga Scenedesmus dimorphus (UTEX strain 1237) were realized in a synthetic culture media, with the addition of a non metabolised and non toxic black dye at different dilutions obtaining an array of equally spaced absorbances, ultimately yielding to a tailored light limitation. The cultures were grown in cylindrical and flat panel photobioreactors under artificial light. The experimental results were analysed with a simple (Lambert-Beer + Monod) growth model to investigate the exploitation criteria for wastewaters as culture media for microalgae
Production and characterization of silver nanoparticles in cultures of the cyanobacterium A. platensis (Spirulina)
The increasing application of Silver nanoparticles in biologically-relevant areas (including production of
textiles, cosmetics, and biomedical devices), where their presence provides a continuous release of silver ions
to provide protection against bacteria and other unwanted microbial contaminants urges adoption of
intrinsically biologically safe production processes. Various species of cyanobacteria and algae have been
known to absorb and take up heavy metal ions. This capability is shown also by Arthrospira platensis
(Spirulina), a cyanobacterium that enjoys the Generally Recognised as Safe (GRAS) status and has been
declared by WHO one among the greatest superfood. The present study aims at investigating the coupling
between the recognised beneficial effects of Spirulina biomass to the antimicrobial activity of Ag nanoparticles
(SNPs).
In this work, Spirulina was grown in sequential cultures targeting biomass production and nanoparticle
formation. The cultures were conditioned during their lifetime in order to assess the effect of pH and added
polysaccharides on the size and on the stability of the obtained SNPs. The synthesized SNPs were
characterized as to their size and stability (Nanosizer), composition (XRD) and structural aspect (Scanning
Electron Microscope)
Design and Bench-Scale Hydrodynamic Testing of Thin-Layer Wavy Photobioreactors
In a thin-volume photobioreactor where a concentrated suspension of microalgae is circulated throughout the established spatial irradiance gradient, microalgal cells experience a time-variable irradiance. Deploying this feature is the most convenient way of obtaining the so-called flashing light effect, improving biomass production in high irradiance. This work investigates the light flashing features of sloping wavy photobioreactors, a recently proposed type, by introducing and validating a computational fluid dynamics (CFD) model. Two characteristic flow zones (straight top-to-bottom stream and local recirculation stream), both effective toward light flashing, have been found and characterized: a recirculation-induced frequency of 3.7 Hz and straight flow-induced frequency of 5.6 Hz were estimated. If the channel slope is increased, the recirculation area becomes less stable while the recirculation frequency is nearly constant with flow rate. The validated CFD model is a mighty tool that could be reliably used to further increase the flashing frequency by optimizing the design, dimensions, installation, and operational parameters of the sloping wavy photobioreactor
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