In this work, brown alga (Sargassum plagiophyllum) was utilized as a reinforcement material to produce wheat gluten (WG) biocomposites. The effect of brown alga powder (BP) content and sonication treatments of BP on the properties of the obtained WG biocomposites were characterized. Adding 1 wt% BP to WG increased the tensile strength by 77% compared to neat WG and could delay the degradation process of the WG biocomposites due to the good interaction between BP and the WG matrix. When the time and amplitude of BP sonication was increased, the tensile strength of the obtained WG biocomposites slightly decreased, but still remained higher than the tensile strength of the neat WG. Therefore, this work presents an efficient reinforcement material and a potential treatment process to produce promising alternative biocomposites for the production of environment friendly materials.biopolymers and renewable polymers, molding, proteins | INTRODUCTIONWheat gluten (WG) is a by-product of wheat starch production and other food processes. 1,2 The structure of WG comprises two major proteins, gliadin, and glutenin. WG is prominent among plant proteins (WG, soya, and zein), due to its wide availability, renewability and biodegradability and is used commercially in various applications for its unique viscoelastic properties. It is used as a binder for paper coatings, in adhesive tapes, cosmetics, textiles, and medical and bioplastic packaging. 3,4 For the last of those applications, WG can be processed into bioplastic by the addition of plasticizers before treatment either by solvent casting or common thermoplastic processes such as extrusion or thermomolding. 2,4,5 However, the performance of WG-based bioplastics is severely limited when compared with materials based on synthetic polymers. The strength and thermal stability of WG-based bioplastics are low and WG-based bioplastics have a strong tendency to absorb moisture. 3,5 One way to improve the performance of bioplastics is to include reinforcing filler materials and recently, the reinforcement of WG-based bioplastics with bio-based materials has gained increasing attention. The filler materials used have included rubber wood sawdust, fish scale, shrimp shell, palm empty fruit bunch fiber, banana fiber and pine char. The method is simple and highly effective and these bio-based materials are sustainable