Phycoerythrin (PE) present on the outer phycobilisome (PBS) rods in Fremyella diplosiphon contains covalently attached phycoerythrobilin (PEB) chromophores for efficient photosynthetic light capture. Chromophore ligation on phycobiliprotein subunits occurs through bilin lyase catalyzed reactions. The cpeY and cpeZ genes in F. diplosiphon were shown to attach PEB on alph-82 of PE. To better understand the individual functions of cpeY and cpeZ in native cyanobacteria, we characterized PBS and PE purified from cpeY and cpeZ deletion mutants and compared them with wild type (WT). Both cpeY and cpeZ mutants generated much less PE than WT as well as assembling much less PE into the PBS. PE purified from cpeY mutant had phycocyanobilin on alpha-PE in place of PEB. The mutation of cpeZ affected the biosynthesis and accumulation of beta-PE with a red-shifted absorbance compared to WT PE. CpeY was shown to function as a bilin lyase, and CpeZ possibly functions as a chaperone.

Synechococcus, a genus of photosynthetic cyanobacteria, is the second most abundant oxygenic microorganism in the marine environment that contributes significantly to the ocean’s primary productivity (Humily et al. 2013; Shukla et al. 2012). They are capable of utilizing available light of different wavelengths in the visible spectrum to perform photosynthesis and fix carbon dioxide and thus inhabit a wide range of light niches in the ocean along horizontal (coast vs offshore) and vertical gradients (depth) (Humily et al. 2013). A gene encoding a putative lyase isomerase, mpeQ, is present in phycoerythrin-II encoding operon that is expressed constitutively and a gene encoding putative lyase, mpeW, is present in CA-4 genomic island whose expression is regulated by ambient light color were identified and characterized in Synechococcus sp. A15- 62, a strain having a blue light specialist phenotype in its basal state. The amino acid sequence of the proteins encoded by mpeW and mpeQ are similar to other characterized lyases and these genes are conserved in cyanobacteria strains containing the CA4-B genomic island, which controls CA4 (Humily et al. 2013). The MpeW and MpeQ proteins were produced in E. coli and co-expressed with recombinant HT-MpeA and phycoerythrobilin (PEB) synthesis machinery. Site directed mutants of the HT-MpeA protein (Cys75Ala, Cys83Ala, Cys140Ala) were used to investigate the site for bilin attachment. The recombinant protein co-expression experiments of MpeQ and MpeW demonstrated that MpeQ attaches phycoerythrobilin (PEB) to cysteine-83 site on a-phycoerythrin II and isomerizes it to phycourobilin (PUB) and MpeW attaches phycoerythrobilin (PEB) to the same site.

A multi-plasmid, co-expression system was used to recreate the biosynthetic pathway for phycobiliproteins from the cyanobacterium Synechococcus sp. PCC 7002 in E. coli. This system efficiently produced chromophorylated allophycocyanin (ApcA/ApcB), -phycocyanin, and -phycocyanin. This system was used to demonstrate that CpcS-I and CpcU proteins are both required attaching PCB to allophycocyanin subunits ApcD (AP-B) and ApcF (18). The N-terminal, AP-like domain of ApcE (LCM99) was produced in soluble form and shown to have intrinsic bilin lyase activity. In addition, this system was used to chromophorylated CpcA from Synechococystis sp. PCC 6803 with a non-cognate bilin; PEB with the aid of CpcEF type bilin lyase. However, the CpcSU type lyase displays much higher specificity for PCB (the native bilin in these species) than PEB. Next, using a heterologous, co-expression system in E. coli, the PEB ligation activity of putative lyase subunits CpeY, CpeZ, and CpeS was tested on the CpeA and CpeB subunits from F. diplosiphon. CpeY/CpeZ was found to ligate PEB on CpeA, although CpeY alone had only 60% chromophorylation activity compared to CpeYZ together. Studies with site-directed variants of CpeA (C82S and C139S), revealed that CpeY/CpeZ attached PEB at Cys-82 on HT-CpeA. The CpeS bilin lyase ligated PEB at both Cys-82 and Cys-139 of CpeA, but the yield of attached PEB at Cys 82 was much lower than observed with CpeY or CpeY/CpeZ. However, CpeS efficiently attached PEB to Cys-82 of CpeB. Purified PE from cpeY deletion mutants in F. diplosiphon was found to have PCB added on α-PE instead of PEB, which was likely performed by CpcEF in vivo. However, a cpeZ knock-out mutant is affected in chromophorylation of both  and  subunits of PE with a red-shifted absorbance compared to wild type PE probably due to missing PEB on PE subunits. Next a new type of bilin lyase isomerase for PEII ( subunit) named MpeZ from Synechococcus sp. RS 9916, was analyzed using the E. coli heterologous coexpression system. MpeZ acted as bilin lyase/isomerase chromophorylating α-PEII (MpeA) with PUB on Cys 83.

Cyanobacteria are photosynthetic prokaryotes that able to produce oxygen. They have light harvesting complexes called phycobilisomes (PBS). PBS are generally composed of an allophycocyanin core with phycocyanin and phycoerythrin rods connected to the core. PBS are able to efficiently harvest light energy from different wavelengths of visible light due to the evolution of PBP. Phycoerythrin has five chromophores that are attached to six cysteine residues and is essential for efficient green light capture and transfer of energy for use in photosynthesis. The attachment of these chromophores to PBP is facilitated by enzymes known as bilin lyases. In this study, we characterize and explore the role of enzymes that are involved in the biosynthesis of phycoerythrin in cyanobacteria. Biochemical and molecular techniques were used in the characterization of these proteins to gain a better understanding of their roles in the post-translational modification of phycobiliprotein. In F. diplosipohon, the lyase activity of CpeT was characterized and studied using a heterologous, co-expression system in E. coli. It was determined that CpeT was able to ligate PEB to Cys-165 of CpeB in the presence of CpeZ, a chaperone-like protein. Next, the roles of three proteins, MpeY from RS9916 and MpeQ and MpeW from A15-62, were analyzed using a combination of gene-interruption mutants and recombinant protein expression techniques. The absence of mpeY resulted in the reduction of PEB chromophorylation of MpeA in green light conditions, and recombinant protein coexpression confirmed that MpeY was responsible for PEB attachment to Cys-83 of MpeA. The interruption of mpeQ in A15-62 resulted in a reduced PUB phenotype in MpeA in blue light. Recombinant protein expressions revealed that MpeQ was a lyase-isomerase responsible for the attachment of PUB to Cys-83 of MpeA. Two regulatory proteins located in two conserved configurations of a genomic island present in species that are able to change their phycobilin content in response to different light environments, known as Type-IV chromatic acclimation (CA4), were investigated. FciA and FciB from RS9916 were studied using gene interruption mutants from RS9916 and they were found to be responsible for the CA4 response in CA4-A containing species of Synechococcus.

abstract: Photosynthesis is the primary source of energy for most living organisms. Light harvesting complexes (LHC) play a vital role in harvesting sunlight and passing it on to the protein complexes of the electron transfer chain which create the electrochemical potential across the membrane which drives ATP synthesis. phycobilisomes (PBS) are the most important LHCs in cyanobacteria. PBS is a complex of three light harvesting proteins: phycoerythrin (PE), phycocyanin (PC) and allophycocyanin (APC). This work has been done on a newly discovered cyanobacterium called Leptolyngbya Heron Island (L.HI). This study has three important goals: 1) Sequencing, assembly and annotation of the L.HI genome - Since this is a newly discovered cyanobacterium, its genome was not previously elucidated. Illumina sequencing, a type of next generation sequencing (NGS) technology was employed to sequence the genome. Unfortunately, the natural isolate contained other contaminating and potentially symbiotic bacterial populations. A novel bioinformatics strategy for separating DNA from contaminating bacterial populations from that of L.HI was devised which involves a combination of tetranucleotide frequency, %(G+C), BLAST analysis and gene annotation. 2) Structural elucidation of phycoerythrin - Phycoerythrin is the most important protein in the PBS assembly because it is one of the few light harvesting proteins which absorbs green light. The protein was crystallized and its structure solved to a resolution of 2Å. This protein contains two chemically distinct types of chromophores: phycourobilin and phycoerythrobilin. Energy transfer calculations indicate that there is unidirectional flow of energy from phycourobilin to phycoerythrobilin. Energy transfer time constants using Forster energy transfer theory have been found to be consistent with experimental data available in literature. 3) Effect of chromatic acclimation on photosystems - Chromatic acclimation is a phenomenon in which an organism modulates the ratio of PE/PC with change in light conditions. Our investigation in case of L.HI has revealed that the PE is expressed more in green light than PC in red light. This leads to unequal harvesting of light in these two states. Therefore, photosystem II expression is increased in red-light acclimatized cells coupled with an increase in number of PBS. / Dissertation/Thesis / Ph.D. Chemistry 2014

Reported in this dissertation are the results of investigations performed at the New Orleans Center for Mass Spectrometry at the University of New Orleans. The projects that are detailed in the coming pages take on a variety of subjects, but a common thread is that each employs matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to solve a problem. Fundamental aspects of MALDI in-plume ionization are implicated in the introduction of a newly developed electron-transfer secondary ionization matrix. The remaining projects are related to the ever expanding field of proteomics. Mass spectrometry was used to investigate the site specificity of a newly developed bilin-lyase enzyme, a new approach was developed to distinguish between A-ring and D-ring attachment of bilins, and F. grandis protein expression pattern was investigated in several tissues. All obtained results were acquired using a MALDI TOF/TOF mass spectrometer. The sensitivity, mass accuracy, mass resolution and the ability to perform collision induced decomposition (CID) experiments were all valuable features that served to raise the quality of data, and thereby improved the detail of inferences to be drawn for the different projects.

Cyanobacteria are photosynthetic organisms that efficiently capture light by utilizing the light-harvesting complexes called phycobilisomes. In many cyanobacteria, phycobilisomes are composed of an allophycocyanin core with phycocyanin and phycoerythrin (PE) rods radiating from the core. These phycobiliproteins have multiple bilin chromophores, such as phycoerythrobilin (PEB), covalently attached to specific cysteine (Cys) residues for efficient photosynthetic light capture. Chromophore ligation on phycobiliprotein subunits occurs through bilin lyase catalyzed reactions. This study mainly focuses on characterizing the roles of enzymes that are involved in the biosynthetic pathway of the phycobiliproteins within two cyanobacteria Thermosynechococcus elongatus and Fremyella diplosiphon. A combination of molecular and biochemical techniques were used to better understand the roles of these proteins in the post-translational modification and/or stability of phycobiliproteins. Using a heterologous plasmid coexpression system in E. coli, recombinant CpcS-III from T. elongatus was shown to ligate three different bilins to both subunits of allophycocyanin and to the beta subunit of phycocyanin, thus, acting as a bilin lyase. The crystal structure of CpcS-III was also solved, the first bilin lyase structure. Next, the roles of three proteins from F. diplosiphon CpeY, CpeZ, and CpeF were analyzed using a combination of gene knock-out mutants and recombinant protein expression techniques. In the absence of cpeY, chromophorylation to the alpha subunit of PE at Cys-82 was reduced, coinciding with the recombinant data that CpeY is the lyase that attaches PEB to this site. Removing cpeZ from the genome resulted in the destabilization and reduced accumulation of PE, especially the beta subunit CpeB. Recombinant CpeZ was shown to act like a chaperone-like protein and increased the solubility and fluorescence of both recombinant and native CpeB by increasing the stability of the phycobiliprotein and/or by increasing the activities of other lyases. The deletion of cpeF resulted in a reduced-PE phenotype with the doubly attached PEB missing from CpeB at Cys-48/Cys-59. Recombinant CpeF was shown to ligate PEB to CpeB-Cys-48/Cys-59 in the presence of recombinant CpeS (lyase attaches PEB to CpeB-Cys-80) and CpeZ. CpeF also showed a chaperone-like function by stabilizing CpeB, but its main role appears to be as a bilin lyase.

[ES] La inminente necesidad de un desarrollo sostenible ha influido en el crecimiento de la industria, abriendo el camino para la transición progresiva hacia una bioeconomía sostenible. La evolución de la industria textil, caracterizada por altos niveles de contaminación, exige la continua exploración de alternativas a los recursos fósiles y procesos contaminantes. En este sentido, el presente estudio propone la exploración de una alternativa sostenible de colorantes naturales procedentes de biomasa de algas, para su aplicación en procesos de coloración, seleccionados por su reducido impacto ambiental, tanto en el cultivo de las algas, como en la extracción de colorantes, y su posible aplicación textil. Este estudio tiene como objetivo explorar la viabilidad del uso de colorantes procedentes de algas para su aplicación en procesos de coloración textil, como la tintura por agotamiento y estampación pigmentaria. La selección de micro y macroalgas ha sido realizada según criterios que facilitan un cultivo optimizado y simple, ofreciendo diferentes colores básicos para la industria textil, como son el azul (C-ficocianina), el rojo (R-ficoeritrina), el amarillo (ß-caroteno), y el verde (Clorofila a). Los extractos líquidos concentrados en colorantes se han empleado en los procesos seleccionados de acabado textil, para conferir color a fibras naturales, como el algodón y la lana. La viabilidad de las fuentes alternativas de colorantes sostenibles mencionadas anteriormente ha sido estudiada mediante el análisis de la influencia de ciertos auxiliares de coloración, como son los mordientes. Una serie de mordientes convencionales (metálicos, y recién descubiertos) y biomordientes han sido seleccionados para investigar su capacidad de mejora de las propiedades y eficacia de coloración de los colorantes sostenibles. Asimismo, se han estudiado aproximaciones teóricas relacionados con la posible unión fibras-mordientes-colorantes. La implicación del uso de mordientes en los procesos de tintura por agotamiento y estampación pigmentaria se ha caracterizado a través de la medición de las coordenadas cromáticas del espacio de color; el espectro de reflectancia junto con la fuerza del color. El análisis se ha completado con el cálculo del coeficiente de absorción, en base al colorante remanente en los efluentes del agua residual de tintura (para los procesos de tintura). No obstante, la influencia de los mordientes sobre la calidad de los procesos de coloración ha sido evaluada mediante ensayos de medición de solideces al lavado y a la luz realizados según normativas europeas en vigor. El proceso de tintura por agotamiento se ha optimizado para determinar los valores óptimos para la temperatura, relación de baño de tintura, pH, tiempo de proceso, teniendo en cuenta la sensibilidad de los colorantes frente a los factores degradantes y de proceso. Siguiendo el carácter sostenible del proceso, se ha realizado una evaluación preliminar de los efluentes de aguas residuales de tinturas, a través de mediciones de indicadores como DBO5, DQO, contenido en metales, y el comportamiento frente a un tratamiento biológico de aguas residuales. Igualmente, se investigó el posible valor añadido de los colorantes estudiados, midiendo la capacidad de protección solar y antimicrobiana. El proceso de estampación pigmentaria abordó la investigación de la viabilidad de los colorantes mediante el empleo de la pasta de estampación sintética convencional, completada con la evaluación de la alternativa representada por la pasta de estampación natural, considerando, al mismo tiempo, la disponibilidad comercial de los componentes. Los resultados obtenidos confieren una validación preliminar de la idoneidad de la aplicación de materia colorante procedente de algas en procesos de tintura por agotamiento y la estampación pigmentaria sobre sustratos textiles de algodón y lana, a escala de laboratorio, con elementos clave para las perspectivas de funcionalización textil, abriendo así el camino para futuras investigaciones que hará posible el escalado de los procesos y el uso industrial de materiales alternativos sostenibles en la industria textil. / [CA] La creixent necessitat per a un desenvolupament sostenible ha tingut un gran impacte en el creixement de la indústria, obrint el camí per a la transició progressiva cap a una bioeconomia sostenible. L'evolució de la indústria tèxtil, caracteritzada per els alts nivells de contaminació fomenta la contínua exploració d'alternatives als recursos fòssils i processos contaminants. En aquest sentit, el present estudi proposa l'exploració d'una alternativa sostenible de colorants naturals procedents de biomassa d'algues, per a la seua aplicació en processos de coloració, seleccionats a causa de l'impacte ambiental reduït, generat pel cultiu de les algues, l'extracció de colorants, i la seua possible aplicació tèxtil. Aquest estudi té com a objectiu explorar la viabilitat de l'ús de colorants procedents d'algues per a la seua aplicació en processos de coloració tèxtil, com la tintura per esgotament i estampació pigmentària. La selecció de micro i macroalgues ha sigut realitzada segons criteris que faciliten un cultiu optimitzat i senzill, que proveeix colors bàsics per a la indústria tèxtil, com són el blau (C- ficocianina), el roig (R-ficoeritrina), el groc (ß-caroteno, i el verd (Clorofil·la a) . Els extractes líquids concentrats en colorants s'han emprat en els processos seleccionats d'acabat tèxtil, per a conferir color a fibres naturals, com el cotó i la llana. La viabilitat de les fonts alternatives de colorants sostenibles mencionades anteriorment ha sigut abordada per mitjà de l'anàlisi de la influència de certs auxiliars de coloració, com són els mordents. Una sèrie de mordents convencionals, metàl·lics, acabats de descobrir i bio mordents ha sigut seleccionada per a investigar la seua capacitat de millora de les propietats i eficàcia de coloració dels colorants sostenibles. A més a més, es va estudiar aproximacions teòriques relacionades amb la unió plausible entre fibres-mordents-colorants. La implicació de l'ús de mordents en els processos de tintura per esgotament i estampació pigmentària s'ha analitzat mitjançantassajos de caracterització, contemplant la caracterització objectiva del color per mitjà del mesurament de les coordenades cromàtiques de l'espai de color; l'espectre de reflectància junt amb la força del color; anàlisi completada pel càlcul del coeficient d'absorció, a base del colorant romanent en els efluents de l'aigua residual de tintura (per als processos de tintura). No obstant això, la influència dels mordents sobre la qualitat dels processos de coloració ha sigut avaluada per mitjà d'assajos de mesurament de solideses al llavat i a la llum realitzats segons normatives europees en vigor. El procés de tintura per esgotament ha sigut optimitzat per a determinar els valors òptims per a la temperatura, relació de bany de tintura, pH, temps de procés, valorant el caràcter sensible dels colorants front als agents degradants i de procés. Recolzant el caràcter sostenible del procés, s'ha realitzat una evaluación preliminar dels afluents d'aigües residuals de tintures, mitjançant mesuraments d'indicadors, com DBO5, DQO, contingut en metalls, i el comportament enfront d'un tractament biològic d'aigües residuals. Igualment, es va investigar el possible valor afegit dels colorants procedents d'algues, mesurant la capacitat de protecció solar i antimicrobiana. El procés d'estampació pigmentària va abordar la investigació de la viabilitat dels colorants per mitjà de l'ocupació de la pasta d'estampació sintètica convencional, completada amb l'avaluació de l'alternativa representada per la pasta d'estampació natural, considerant, al mateix temps, la disponibilitat comercial dels ingredients. Els resultats obtinguts confereixen una validació preliminar de la idoneïtat de l'aplicació de matèria colorant procedent d'algues en processos de tintura per esgotament i l'estampació pigmentària sobre substrats tèxtils de cotó i llana, a escala de laboratori, amb elements clau per a les perspectives de funcionalització tèxtil, obrint així el camí per a futures investigacions que farà possible l'escalat dels processos i l'ús industrial de materials alternatius sostenibles a la indústria tèxtil. / [EN] The crucial need for sustainable development has an immense impact on industrial evolution paving the path for a progressive transition towards a sustainable bioeconomy. Considering the pollutant evolution of the textile industry, approaches to exploring environmentally friendly alternatives to fossil-based resources and polluting processes have become the most current practice nowadays. In this sense, this study proposes the exploration of a sustainable alternative colorant material for coloration applications, from algae-based feedstock, considering the reduced environmental pressure embroiled by algae cultivation, colorant extraction, and its possible further textile application. This study explores the viability of the use of algae-based colorants for their application in exhaustion dyeing and pigment printing coloration techniques for the textile industry. Micro and macroalgae strains selection was performed according to criteria ensuring facile and optimized cultivation and the provision of basic colors for the textile industry as blue (C-phycocyanin), red (R-phycoerythrin), yellow (ß-carotene), and green (Chlorophyll-a). Liquid colorant-rich extracts were employed in the selected textile finishing processes on natural fibers, like cotton and wool. To approach the viability of these alternative sustainable colorants and enhance coloration properties and efficiencies, a series of auxiliaries were assessed, as conventional metallic and newly discovered mordants, and biomordants. Theoretical assumptions related to the plausible bonding among fibers-mordants-colorants were approximated. The auxiliaries implication in exhaustion dyeing and pigment printing processes were analyzed through a series of characterization tests, envisaging objective color characterization determined by the measurement of CIELab color coordinates; reflectance spectrum, and color strength approaching the depth of the coloration; completed by the calculation of the absorption coefficient, based on the remaining colorant matter in the wastewater effluents (for the dyeing process). Nevertheless, the mordants' influence on the quality of the coloration process was assessed through laundering and lightfastness measured according to European standards for textiles characterization. The dyeing exhaustion process was also subjected to parameters optimization in terms of the definition of optimum temperature, dyeing liquor ratio, pH, and time, considering the colorants' sensibilities for degrading and processing agents. A preliminary nearing towards the dyeing wastewater effluent quality assessment supporting the sustainability character of the process was performed through the measurement of basic water characterization indicators as BOD5, COD, metal content, and behavior against biological wastewater treatment. Furthermore, the possible added value of the algae-based colorants was investigated by measuring the antimicrobial and solar protection capacity, enlarging the application prospects of these innovative raw materials for textile applications. The pigment printing process approached the research of the feasibility of the colorants by employing the conventional synthetic printing paste, completed with the assessment of alternative natural printing paste, considering, at the same time the commercial availability of ingredients. The obtained results confer a preliminary validation of the suitability of the application of algae-based colorant matter in exhaustion dyeing and pigment printing of cotton and wool, at laboratory scale, with key elements for textile functionalization perspectives, thus paving the path for further investigation which will make possible the upscaling of the processes and industrial use of alternative sustainable materials in the textile industry. / Moldovan, S. (2021). Dyeing and printing Natural Fibers with Algae-Based Colorants [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/180349 / TESIS

Though numerous valuable compounds from red algae already experience high demand in medicine, nutrition, and different branches of industry, these organisms are still recognized as an underexploited resource. This study provides a comprehensive characterization of the chemical composition of 15 Arctic red algal species from the perspective of their practical relevance in medicine and the food industry. We show that several virtually unstudied species may be regarded as promising sources of different valuable metabolites and minerals. Thus, several filamentous ceramialean algae (Ceramium virgatum, Polysiphonia stricta, Savoiea arctica) had total protein content of 20–32% of dry weight, which is comparable to or higher than that of already commercially exploited species (Palmaria palmata, Porphyra sp.). Moreover, ceramialean algae contained high amounts of pigments, macronutrients, and ascorbic acid. Euthora cristata (Gigartinales) accumulated free essential amino acids, taurine, pantothenic acid, and floridoside. Thalli of P. palmata and C. virgatum contained the highest amounts of the nonproteinogenic amino acid β-alanine (9.1 and 3.2 μM g−1 DW, respectively). Several red algae tend to accumulate heavy metals; although this may limit their application in the food industry, it makes them promising candidates for phytoremediation or the use as bioindicators.

La présente étude s’attache à étudier l’effet d’une source de carbone organique sélectionnée sur la croissance et la production de métabolites de la microalgue rouge Porphyridium marinum. Cette dernière s’est montrée incapable de se multiplier en hétérotrophie, en absence totale de lumière. Cependant, en condition mixotrophique la production de biomasse, lipides et de phycobiliprotéines par P. marinum a été améliorée en comparaison avec la condition autotrophique. Les teneurs en exopolysaccharides ont été presque similaires dans les deux conditions. Dans le but de valoriser ces métabolites, l’effet antioxydant, antibactérien, antibiofilm et anticancéreux ont été testés. L’exopolysaccharide de P. marinum ainsi que ses dérivés de faible poids moléculaire (EPS-2P et EPS-5P) ont tous présenté des activités antibactériennes et antibiofilm à différentes concentrations. Cependant l’EPS-2P et l’EPS-5P ont été jugés plus efficaces pour l’activité anticancéreuse contre les cellules de cancer de sein. D’autre part, la production du pigment majoritaire des microalgues rouges, la B-phycoerythrine (B-PE), a été optimisée moyennant des plans d’expériences adaptés. Une teneur de 40 mg/g MS a été obtenue en faisant varier la concentration en NaNO3, K2HPO4 et solution métallique ainsi que l’intensité lumineuse. Après purification, la molécule optimisée a montré une activité antioxydante en termes de piégeage des radicaux libres DPPH, chélation et réduction des ions de fer et inhibition de la décoloration du β-carotène. Nos données suggèrent alors que les métabolites produits par la microalgue rouge P. marinum peuvent être potentiellement utilisé dans plusieurs applications à savoir cosmétiques et pharmaceutiques. / The present study investigates the effect of a selected organic carbon source on the growth and production of metabolites of the red microalga Porphyridium marinum. The latter has been unable to multiply in heterotrophy, in total absence of light. However, in mixotrophic condition the productions of biomass, lipids and phycobiliproteins by P. marinum have been improved in comparison with the autotrophic condition. The contents of exopolysaccharide were almost similar under both conditions. In order to valorize these metabolites, the antioxidant, antibacterial, antibiofilm and anticancer effect were tested. The exopolysaccharide of P. marinum as well as its low molecular weight derivatives (EPS-2P and EPS-5P) have all exhibited antibacterial and antibiofilm activities at different concentrations. However, EPS-2P and EPS-5P were found to be more effective for anti-cancer activity against breast cancer cells. On the other hand, the production of the majority pigment of red microalgae, B-phycoerythrin (B-PE), has been optimized by means of adapted experimental plans. A content of 40 mg/g DW was obtained by varying the concentration of NaNO3, K2HPO4 and metal solution as well as the light intensity. After purification, the optimized molecule showed antioxidant activity in terms of free radical scavenging DPPH, chelation and reduction of iron ions and β-carotene bleachinginhibition. Our data suggest that the metabolites produced by the red microalga P. marinum may be potentially used in several applications namely cosmetic and pharmaceutical.