Biorefining of microalgae: from harvesting to biofuel production

Aquesta tesi es centra en la modernització del procés de bio-refinat de microalgues mitjançant tecnologia de membrana. El projecte busca l'optimització de: recol·lecció, ruptura cel·lular, fraccionament de carbohidrats, proteïnes i lípids i desenvolupament d'un reactor de membrana catalítica per a la transesterificació per obtenir biodièsel. La reducció de costos es pot aconseguir trobant solucions més barates i millors per a cada pas. En la primera etapa, es va realitzar la filtració utilitzant membranes polimèriques d'ABS de fabricació pròpia, així com altres disponibles comercialment, per comprovar el seu rendiment en la deshidratació de microalgues. Aquest estudi inclou la preparació i caracterització de membranes d'ABS usant diferents tècniques. A més, es va realitzar la comparació de dos mètodes de filtració, flux creuat i dinàmic per comparar la viabilitat de les membranes afectades per embrutiment. En la segona etapa, es va realitzar la deshidratació a escala pilot de dues espècies de microalgues, Chlorella sorokiniana i Dunaliella tertiolecta per sedimentació i filtració dinàmica. L'objectiu va ser reduir els costos de deshidratació de microalgues amb un cost menor al de centrifugació. bio-refinat de microalgues aigües avall. En la quarta etapa, es va realitzar la comparació de nous reactors de membrana catalítica i inert per a la producció de biodièsel amb òxid d'estronci com a catalitzador heterogeni. Els principals objectius van ser identificar un catalitzador adequat, triar la tècnica d'immobilització adequada, establir la membrana amb la mida de porus adequat i controlar la reacció i el procés de separació.microalgues amb diferents característiques de paret cel·lular. L'objectiu d'aquest treball va ser millorar el procés de bio-refinat de microalgues aigües avall. En la quarta etapa, es va realitzar la comparació de nous reactors de membrana catalítica i inert per a la producció de biodièsel amb òxid d'estronci com a catalitzador heterogeni. Els principals objectius van ser identificar un catalitzador adequat, triar la tècnica d'immobilització adequada, establir la membrana amb la mida de porus adequat i controlar la reacció i el procés de separació.Esta tesis se centra en la modernización del proceso de biorefinado de microalgas mediante tecnología de membrana. El proyecto busca la optimización de: recolección, ruptura celular, fraccionamiento de carbohidratos, proteínas y lípidos y desarrollo de un reactor de membrana catalítica para la transesterificación para obtener biodiesel. La reducción de costos se puede lograr encontrando soluciones más baratas y mejores para cada paso. En la primera etapa, se realizó la filtración utilizando membranas poliméricas de ABS de fabricación propia, así como otras disponibles comercialmente, para comprobar su rendimiento en la deshidratación de microalgas. Este estudio incluye la preparación y caracterización de membranas de ABS usando diferentes técnicas. Además, se realizó la comparación de dos métodos de filtración, flujo cruzado y dinámico para comparar la viabilidad de las membranas afectadas por ensuciamiento. En la segunda etapa, se realizó la deshidratación a escala piloto de dos especies de microalgas, Chlorella sorokiniana y Dunaliella tertiolecta por sedimentación y filtración dinámica. El objetivo fue reducir los costos de deshidratación de microalgas con un costo menor al de centrifugación. En la tercera etapa, se estudió la disrupción celular y el fraccionamiento para la recuperación de lípidos, azúcares y proteínas usando explosión de vapor, flujo cruzado y filtración dinámica de membrana. Se probaron varias especies de microalgas con diferentes características de pared celular. El objetivo de este trabajo fue mejorar el proceso de biorrefinado de microalgas aguas abajo. En la cuarta etapa, se realizó la comparación de nuevos reactores de membrana catalítica e inerte para la producción de biodiesel con óxido de estroncio como catalizador heterogéneo. Los principales objetivos fueron identificar un catalizador adecuado, elegir la técnica de inmovilización adecuada, establecer la membrana con el tamaño de poro adecuado y controlar la reacción y el proceso de separación.his thesis focuses on the modernization of the downstream process of microalgae biorefining by membrane technology. The project concerns the optimization of: harvesting, cell disruption, carbohydrates, proteins and lipids fractionation and development of catalytic membrane reactor for transesterification to obtain biodiesel. Cost reduction of the overall process can be achieved by finding cheaper solutions for each step. In the first stage the filtration using own-made ABS polymeric membranes as well as the commercially available ones was run to check their performance for microalgae dewatering. This study included ABS membranes preparation and characterization using different techniques. Also, the comparison of two filtration methods, cross-flow and dynamic was performed to compare the viability of membranes affected by a fouling and a cake formation. In a second stage, the pilot scale dewatering of two microalgae specie, Chlorella sorokiniana and Dunaliella tertiolecta by sedimentation followed by dynamic filtration was performed. The objective of the combined process was to reduce microalgae dewatering costs since sedimentation offers a very cheap operation and membrane filtration offers total rejection with high final concentrations at a lower cost than centrifugation. In a third stage cell disruption and fractionation for lipids, sugars and proteins recovery was studied. Acid-catalysed

PVDF Membrane Morphology—Influence of Polymer Molecular Weight and Preparation Temperature

In this study, we successfully prepared nine non-woven, supported polyvinylidene fluoride (PVDF) membranes, using a phase inversion precipitation method, starting from a 15 wt % PVDF solution in N-methyl-2-pyrrolidone. Various membrane morphologies were obtained by using (1) PVDF polymers, with diverse molecular weights ranging from 300 to 700 kDa, and (2) different temperature coagulation baths (20, 40, and 60 ± 2 °C) used for the film precipitation. An environmental scanning electron microscope (ESEM) was used for surface and cross-section morphology characterization. An atomic force microscope (AFM) was employed to investigate surface roughness, while a contact angle (CA) instrument was used for membrane hydrophobicity studies. Fourier transform infrared spectroscopy (FTIR) results show that the fabricated membranes are formed by a mixture of TGTG’ chains, in α phase crystalline domains, and all-TTTT trans planar zigzag chains characteristic to β phase. Moreover, generated results indicate that the phases’ content and membrane morphologies depend on the polymer molecular weight and conditions used for the membranes’ preparation. The diversity of fabricated membranes could be applied by the End User Industries for different applications

Medical Plaster Enhancement by Coating with <i>Cistus</i> L. Extracts within a Chitosan Matrix: From Natural Complexity to Health Care Simplicity

Our investigation was focused on the preparation and characterization of novel plasters based on Carboxymethyl Chitosan derivative (CMC), to be used for the treatment of radiation dermatitis with Biologic Active Compounds (BACs) in a moist wound-healing environment. After performing the extraction and characterization of BACs from Cistus L., we optimized the BACs/CMC solution for subsequent plaster preparation. Then, plasters were prepared by dip-coating with a different number of layers, and we characterized them by Environmental Scanning Electron Microscopy (ESEM), Contact Angle (CA) and release tests in water for 24 h. Taking into account the flexibility of the plasters and the amount of released BACs after 24 h, the sample obtained after two dip-coating steps (2La) appeared promising in regard to comfortable mechanical properties and active principles administration. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test performed on keratinocytes cultured in standard medium shows that cells treated with released extract from 2La start to proliferate, extend cellular viability and form colonies typical for epidermal cells

Preparation and characterization of UV‐curable acrylic membranes embedding natural antioxidants

We examine the behaviour of acrylic resin‐based membranes containing natural antioxidants, such as Galla Chinensis tea powder extract (TP) and Taiwanese green propolis (TGP), in different concentrations ranging between 5 and 20 wt %. Membrane morphology was investigated by means of Environmental Scanning Electron Microscopy (ESEM), while the UV‐curing reaction was monitored by Fourier‐Transform Infra‐red (FTIR) spectroscopy. In most cases Thermogravimetric (TG), Differential Scanning Calorimetric (DSC) and Dynamo‐mechanical Thermal (DMT) analyses showed that the desirable characteristics of the UV‐cured acrylic resin are not substantially altered by the presence of the organic fillers. The release kinetics of polyphenols and flavonoids, determined in water for TP‐containing membranes (ETx) and in ethanol/water mixture (7:3 v/v) for TGP‐containing ones (EPx), was satisfactory, reaching a plateau after 24 h. Finally, preliminary antibacterial tests against S. Epidermidis were performed on the membranes with higher additive amount and gave positive results for ET‐type; on the contrary, no inhibitory effect was observed for the tested EP‐type membranes

Ultrasound-assisted extraction of biologically active compounds and their successive concentration by using membrane processes

Sideritis scardica and Sideritis syriaca are considered highly valuable plant materials and their total polyphenols (TP) and total flavonoids (TF) extracts can be employed in nutraceutics and cosmetics. A two-step process was proposed consisting in the ultrasound-assisted extraction (UAE) and concentration of the biologically active compounds via nanofiltration (NF). An extensive comparison between UAE and conventional high-temperature stirring was performed, taking into account the effect of process parameters such as solvent, temperature and ultrasonication. In terms of radical scavenging activity and time optimization, UAE was found more effective, providing – after only 1 h – extraction yields comparable to 20 h of the conventional thermo-mechanical method. The extract was then concentrated by nanofiltration in tangential mode at 20 bar using 300 and 500 Da cut-off Duramem membranes. Permeate and rejection flux was monitored during the filtration process. The lower molecular weight membrane showed higher permeability towards TP and TF and contributed to a more stable flux and lower fouling processes. To predict operational drawbacks, computational fluid dynamic simulations were performed to model the complex rotational flow occurring during membrane filtration