Le milieu marin constitue la plus grande partie de la biosphère et contient les formes les plus anciennes et les plus variées de la vie. Les espèces microbiennes, relativement négligées jusqu’à présent, pourraient bien être le principal gisement de nouvelles molécules des prochaines décennies grâce à leurs adaptations à un environnement marin atypique et/ou à des conditions extrêmes (zones hydrothermales, sédiments des fonds sous-marins, lagunes hyper-salines, continent arctique et antarctique, tapis microbiens…). La Nouvelle-Calédonie est dotée de milieux naturels littoraux, côtiers et marins au sein desquels existent des gradients thermiques, d’hypersalure/dessalure, de chocs UV, de pH, d’évaporation, d’inondation/exondation… qui déterminent des habitats atypiques dans lesquels les micro-organismes doivent développer des stratégies adaptatives et de défense potentiellement uniques. Un travail de bioprospection de ces milieux atypiques a ainsi permis la création d’une souchothèque riche à ce jour de 771 isolats bactériens néo-calédoniens. Sur la base de cette collection, des études ont été engagées pour la recherche et la caractérisation de biopolymères de type exopolysaccharides (EPS) et polyhydroxyalcanoates (PHA). Les EPS sont des complexes osidiques de grande taille dont la composition est variable selon l’organisme producteur. Les PHAs sont des macromolécules formées de liaisons ester présentant de fortes similitudes avec les plastiques issues de la pétrochimie mais sont totalement biodégradables et biocompatibles. Les débouchés pour la valorisation des biopolymères marins sont très variés et touche plusieurs secteurs comme la cosmétique (gélifiant épaississant, antirides, etc.) la santé (immunostimulation, anticoagulant, cicatrisant), l’agroalimentaire, la bioremédiation les emballages, l’enrobage… Les criblages réalisés sur l’ensemble de la collection pour les deux types de polymères ont permis de mettre en évidence qu’une part importante des souches de la collection étaient potentiellement capables de sécréter ces polymères. À l’heure actuelle, 10 types d’EPS et 5 types de PHAs ont été produits et caractérisés afin de cibler des domaines d’applications. L’étude des bactéries marines pour leur faculté à produire des polymères est donc un secteur en pleine expansion et les premiers résultats montrent que ce type de biotechnologies pourrait constituer une perspective de développement intéressante pour la Nouvelle-Calédonie. / Previous works on marine bacteria led to the discovery of molecules of great biotechnological interest. Under unusual physical and chemical conditions some microorganisms have developed various survival strategies including exopolysaccharides (EPS) and Poly-3-hydroxyalkanoates (PHAs) production. Due to their many interesting biological, physical and chemical properties, those polymers have found applications in many industrial sectors. Due to interesting physical and chemical properties, EPS can find applications in many industrial sectors including the food industry, cosmetics, for oil and metal recovery from industrial waste and in the mining industry as well. During the last decades EPS have also been demonstrated as interesting bioactive molecules with many applications for human health. PHAs are biopolyesters accumulated as granules in bacteria in order to endure long starving periods. Those biodegradable biopolymers can be used as an alternative to petroleum derived polymers and can be produced from renewable carbon sources. PHAs exhibit a wide variety of properties and structures depending of the carbon source available and the microorganism used for the production. New Caledonia (NC) is frequently referred as a hotspot biodiversity. During a prospection campaign performed in different marine costal ecosystems of NC, a great number (770) of bacteria were isolated from different locations. Screening showed that 55% of the isolates were able to produce under lab conditions EPS and 53% to produce PHA. Partial chemical characterization was performed on purified samples using colorimetric methods, infrared spectrometry (FTIR), gas chromatography (GC) and nuclear magnetic resonance (NMR). Marine bacteria from New Caledonian ecosystems were shown to produce EPS with unusual chemical composition with potential applications in cosmetics. Preliminary experiments also showed high metal-binding capacity with applications in bioremediation. Different PHAs were also produced using different types of sugars and oil as renewable resources. Blue biotechnologies can have various applications in many industrial sectors (Health, food industry, environment, cosmetics etc…) and there is a great international demand for new molecules issue from marine areas. New Caledonian marine bacteria have proved their capacity for producing innovative biopolymers with a wide range of application that can be valuating in on short time period (environment, cosmetics) or at long time (pharmaceutics, surgeries). These applications are promising in order to develop

In the past decade, there has been significant progress in 3D printing research for tissue engineering (TE) using biomaterial inks made from natural and synthetic compounds. These constructs can aid in the regeneration process after tissue loss or injury, but achieving high shape fidelity is a challenge as it affects the construct's physical and biological performance with cells. In parallel with the growth of 3D bioprinting approaches, some marine-origin polymers have been studied due to their biocompatibility, biodegradability, low immunogenicity, and similarities to human extracellular matrix components, making them an excellent alternative to land mammal-origin polymers with reduced disease transmission risk and ethical concerns. In this research, collagen from shark skin, chitosan from squid pens, and fucoidan from brown algae were effectively blended for the manufacturing of an adequate biomaterial ink to achieve a printable, reproducible material with a high shape fidelity and reticulated using four different approaches (phosphate-buffered saline, cell culture medium, 6% CaCl2, and 5 mM Genipin). Materials characterization was composed by filament collapse, fusion behavior, swelling behavior, and rheological and compressive tests, which demonstrated favorable shape fidelity resulting in a stable structure without deformations, and interesting shear recovery properties around the 80% mark. Additionally, live/dead assays were conducted in order to assess the cell viability of an immortalized human mesenchymal stem cell line, seeded directly on the 3D printed constructs, which showed over 90% viable cells. Overall, the Roswell Park Memorial Institute cell culture medium promoted the adequate crosslinking of this biopolymer blend to serve the TE approach, taking advantage of its capacity to hamper pH decrease coming from the acidic biomaterial ink. While the crosslinking occurs, the pH can be easily monitored by the presence of the indicator phenol red in the cell culture medium, which reduces costs and time.