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

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

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

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

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

Analysis of microalgae growth in residual light: A diagnostics tool for low-cost alternative cultural media

Most microalgae grow in photoautotrophy and some benefit from mixotrophy and their growth essentially depends on the effective available light intensity. Non transparent media are frequently obtained as the byproduct of bioprocessing but laboratory testing on the suitability of such media may provide misleading results even in laboratory scale photobioreactors. Chapter 2 Cicci et al. (2013) introduced the procedure for calculating a semi-empirical normalised growth rate accounting for a time-varying light limitation inside symmetric photobioreactors and permitting to cancel out the effects of unknown quantities in the photosynthetic response of the microalgal biomass and help diagnose the nutritional suitability of the composite medium. This paper presents the results of applying the semi-empirical normalised growth rate to microalgal growth experiments carried out on media obtained from an anaerobic cattle digestate and from an olive oil mill wastewater (OOMW) and discusses use, inherent opportunities of the proposed diagnostic tool

Adsorption of phenol/tyrosol from aqueous solutions on macro-reticular aromatic and macro-porous polystyrene cross-linked with divinylbenzene polymeric resins

The current work aims at separating by adsorption of low-molecular-weight organic compounds in a nanofiltration concentrate of the olive mill wastewaters. The experimental investigations on adsorption of phenol/tyrosol in single and binary systems were conducted in batch mode by using the commercially available macroporous resins FPX66 and MN202. The structures of such resins were examined by FTIR before and after adsorption. The operating parameters affecting the adsorption process such as resin dosage, contact time, pH, and initial concentration of phenol/tyrosol were investigated. Fast phenol and tyrosol uptakes were observed for both resins. It can be attributed to their physical properties, for instance high specific area and microporous area. The adsorption selectivity of phenol is larger than tyrosol when using FPX66 resin, but smaller if MN202 resin is used. Acidic pH appeared to be always favourable for the adsorption. A synergetic effect between solutes was observed since adsorption of phenol and tyrosol in the binary systems was faster than the individual sorption of each solute. Five isotherms namely Langmuir, Freundlich, DubininRadushkevich, Temkin and Redlich-Peterson were selected to fit the obtained equilibrium experimental data. Finally, desorption of the examined compounds with ethanol (EtOH) allowed a maximum around 85 % of phenol, and equal to 94 % of tyrosol on FPX66 and MN202 resins