Algal Research 61 (2022) 102565 Available online 19 November 2021 2211-9264/© 2021 Published by Elsevier B.V. Characterization of biodegradable films based on extracellular polymeric substances extracted from the thermophilic microalga Graesiella sp. Wejdene Gongi a, b, * , Juan Luis G´ omez Pinchetti c , Nereida Cordeiro d , Saloua Sadok a , Hatem Ben Ouada a a Laboratory of Blue Biotechnology & Aquatic Bioproducts, National Institute of Marine Sciences and Technologies, 5000 Monastir, Tunisia b National Institute of Agronomy, University of Carthage, Tunis 1082, Tunisia c BEA - Spanish Bank of Algae, Institute of Oceanography and Global Change (IOCAG), University of Las Palmas de Gran Canaria, Muelle de Taliarte s/n, 35214 Telde, Canary Islands, Spain d LB3-Faculty of Science and Engineering, University of Madeira, 9000-390 Funchal, Portugal A R T I C L E INFO Keywords: Graesiella sp. EPS film Physicochemical properties Antioxidant Meat shelf life ABSTRACT In this research, a new type of biodegradable film based on the extracellular polymeric substances (EPS) and isolated from the thermophilic microalga Graesiella sp., was formulated and characterized. The EPS film was 0.221 mm thick. Atomic force microscopy and scanning electron microscopy images revealed a homogeneous character with a lamellar microstructure. The EPS film displayed yellowish color, high transparency, high ul- traviolet barrier properties, and low oxygen (0.008 SI), and water-vapor permeability (0.037 SI). Film tensile strength (16.24 MPa) and elongation at break (4.76%) were in the range of common biofilms and the thermal analyses showed high transition temperature (126 ◦ C) and high thermal stability (up to 800 ◦ C). Compared to ascorbic acid, results indicated that the EPS film shows a higher antioxidant activity, mainly as β-carotene anti- bleaching (84%), DPPH- free radical scavenging ability (80%), and ferrous iron-chelating (55%). Graesiella sp., EPS film effects on beef meat packaging were studied during nine days of cold storage. Compared to polyvinylchloride-packed meat, EPS-packed meat samples showed higher stability of color (redness = 13.6) and pH (5.85) during storage and low proliferation of total viable counts (4.04 CFU⋅g  1 ) and Pseudomonas bacteria (4.09 CFU⋅g  1 ). They also exhibit lower drip loss (9%) and less metmyoglobin (32%), heme iron (4.87 μg⋅g  1 ) total volatile basic nitrogen (TVB-N = 22.96 mg⋅kg  1 ), and lipid oxidation (MDA = 0.025 mg⋅kg  1 ). The obtained results highlight the potential for use of microalgae EPS as a new film- forming material that could be applied in beef meat preservation. 1. Introduction Recently, plastics have become a source of worrying contamination due to their abundance, their persistence in nature, as well as their harmful effects on biodiversity and the environment [1]. Plastics are mainly used as packaging materials, up to 38%, and most are released into the environment after a single-use. Plastic waste, more than 170 million tons in 2017 [2,3], and their additives, including butylated hydroxytoluene (BHT) or butylated hydroxyanisole (BHA), cause serious pollution problems, particularly in soil and water [4,5]. Therefore, extensive research has been conducted to replace common synthetic materials with natural ones [6]. The exploitation of natural materials in the preparation of eco-friendly packaging films has been a new promising issue for meat products safety [7]. Biodegradable films are being successfully used as active packaging in several processed foods, including seafood/meat products and fruits, as oxygen scavengers, barriers to water and light, antibacterial, and anti- browning agents [9]. The bio-based films made from natural polymers have recently attracted considerable interest because of their ecological properties, their safety, and their biodegradability in nature [10]. Natural polysaccharides, proteins, and lipids biopolymers are used for bio-based film preparation. Besides their role as a barrier against the external environment, they provide active functions by prolonging the shelf life and improving the safety and the sensory properties of different products [8]. In recent years, the exploitation of extracellular polymeric substances (EPS) has been of particular interest. However, EPS have not * Corresponding author. E-mail address: gongi.wejden@gmail.com (W. Gongi). Contents lists available at ScienceDirect Algal Research journal homepage: www.elsevier.com/locate/algal https://doi.org/10.1016/j.algal.2021.102565 Received 24 June 2021; Received in revised form 1 November 2021; Accepted 10 November 2021