Citation: Concórdio-Reis, P.; Pereira, J.R.; Alves, V.D.; Nabais, A.R.; Neves, L.A.; Marques, A.C.; Fortunato, E.; Moppert, X.; Guézennec, J.; Reis, M.A.; et al. Characterisation of Films Based on Exopolysaccharides from Alteromonas Strains Isolated from French Polynesia Marine Environments. Polymers 2022, 14, 4442. https://doi.org/10.3390/ polym14204442 Academic Editors: Beom Soo Kim and Przemyslaw P ˛ aczkowski Received: 19 September 2022 Accepted: 18 October 2022 Published: 20 October 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). polymers Article Characterisation of Films Based on Exopolysaccharides from Alteromonas Strains Isolated from French Polynesia Marine Environments Patrícia Concórdio-Reis 1,2 , João R. Pereira 1,2 ,Vítor D. Alves 3 , Ana R. Nabais 4 , Luísa A. Neves 4 , Ana C. Marques 5 , Elvira Fortunato 5 , Xavier Moppert 6 , Jean Guézennec 7 , Maria A.M. Reis 1,2 and Filomena Freitas 1,2, * 1 Associate Laboratory i4HB—Institute for Health and Bioeconomy, NOVA School of Science and Technology, NOVA University of Lisbon, 2829-516 Caparica, Portugal 2 UCIBIO—Applied Molecular Biosciences Unit, Department of Chemistry, NOVA School of Science and Technology, NOVA University of Lisbon, 2829-516 Caparica, Portugal 3 LEAF—Linking Landscape, Environment, Agriculture and Food, Associated Laboratory TERRA, Instituto Superior de Agronomia, Universidade de Lisboa, 1349-017 Lisboa, Portugal 4 LAQV-REQUIMTE, Departmentof Chemistry, NOVA School of Science and Technology, FCT NOVA, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal 5 CENIMAT|i3N, Departmentof Materials Science, School of Science and Technology, NOVA University Lisbon and CEMOP/UNINOVA, 2829-516 Caparica, Portugal 6 Pacific Biotech BP 140 289, Arue Tahiti 98 701, French Polynesia 7 AiMB (Advices in Marine Biotechnology), 17 Rue d’Ouessant, 29280 Plouzané, France * Correspondence: a4406@fct.unl.pt; Tel.: +351-212948357 Abstract: This work assessed the film-forming capacity of exopolysaccharides (EPS) produced by six Alteromonas strains recently isolated from different marine environments in French Polynesia atolls. The films were transparent and resulted in small colour alterations when applied over a coloured surface (ΔE ab below 12.6 in the five different colours tested). Moreover, scanning electron microscopy showed that the EPS films were dense and compact, with a smooth surface. High water vapour permeabilities were observed (2.7–6.1 × 10 −11 mol m −1 s −1 Pa −1 ), which are characteristic of hydrophilic polysaccharide films. The films were also characterised in terms of barrier proper- ties to oxygen and carbon dioxide. Interestingly, different behaviours in terms of their mechanical properties under tensile tests were observed: three of the EPS films were ductile with high elonga- tion at break (ε) (35.6–47.0%), low tensile strength at break ( Ꞇ ) (4.55–11.7 MPa) and low Young’s modulus (εm) (10–93 MPa), whereas the other three were stiffer and more resistant with a higher Ꞇ (16.6–23.6 MPa), lower ε (2.80–5.58%), and higher εm (597–1100 MPa). These properties demon- strate the potential of Alteromonas sp. EPS films to be applied in different areas such as biomedicine, pharmaceuticals, or food packaging. Keywords: Alteromonas sp.; marine bacteria; exopolysaccharide (EPS); films 1. Introduction Petrochemical-based plastics have widespread use in nowadays society due to their low-cost and useful characteristics, that include good mechanical and thermal proper- ties, heat moulding capacity, suitable gas barrier properties, and high transparency [1,2]. However, due to their limited biodegradability which represents a serious environmental and human health threat, those synthetic plastics are expected to be replaced by novel biodegradable materials [3]. Biopolymers, such as polysaccharides, are a promising substi- tute since they are biodegradable, biocompatible, and non-toxic, since they are obtained from renewable resources [1,4–6]. Applications of polysaccharide-based films include food packaging [3], drug delivery systems [7,8], coatings for medical devices [9], and wound Polymers 2022, 14, 4442. https://doi.org/10.3390/polym14204442 https://www.mdpi.com/journal/polymers