Exopolysaccharides from Porphyridium cruentum as a reinforcing agent for chitosan biopolymer-based film

Microalgae exopolysaccharides (EPS), extracted from exhausted culture medium of Porphyridium cruentum, a rhodophyte able to grow in marine environments, may be useful as reinforcing agents in chitosan-based films produced by casting, using glycerol as a plasticizer. EPS were added at 1 and 2 % (w/v). The resulting hydrophilic films, EPS1 and EPS2, respectively, were opaquer than the control (CTR) chitosan-based films without EPS, resulting in increased thickness and solubility, and decreased moisture and water contact angle. EPS1 and EPS2 showed 1.5 and 2.0-fold higher tensile strength and a 2.9- and 16.3-fold higher Young's modulus, respectively, compared to CTR. Conversely, elongation decreased by 1.9- and 8.2-fold for EPS1 and EPS2 compared to CTR. EPS1 and EPS2 showed a homogeneous matrix surface upon SEM analysis, presenting some aggregated particles with increasing EPS concentration. FTIR histograms were not influenced by the EPS concentration used. Thermal analysis showed film degradation occurred in three phases, with no significant enhancement in thermal stability. Soil biodegradability confirmed all films degraded within 35 days. This study demonstrated the feasibility of using industrial microalgae byproducts, such as EPS, as film reinforcement agents, primarily enhancing mechanical strength, thus increasing the possibilities of using these raw materials to produce sustainable food films.