Antibacterial Property and Biodegradability of Bioplastic Products from Gracilaria salicornia And Halimeda opuntia with Zinc Oxide Nanoparticles

Marine algae have attracted a great deal of interest as an excellent source of bioplastic due to their hydrocolloid properties and rich polysaccharide. This research focuses on the development of bioplastic products from Gracilaria salicornia and Halimeda opuntia with Zinc Oxide nanoparticles (ZnONps) found in the coastal water of Alma Beach, Catarman, Northern Samar. The seaweed bioplastic products were subjected to physicochemical and antibacterial property, employing FTIR spectroscopy, UV-Vis spectrophotometer and Scanning Electron Microscopy for analytical analysis after incorporation of biosynthesized Zinc Oxide nanoparticles. The agar was extracted from Gracilaria salicornia through drying, alkaline solution treatment and boiling and freezing method. Meanwhile, the crude extraction method was used for Halimeda opuntia. The resulting films exhibited favorable mechanical property including enhanced tensile strength, elongation at break, UV resistance, and antibacterial activity against Staphylococcus aureus. A micrometre calliper was used to measure the film's thickness; tensile strength and elongation at break was determined using sliver weights; solubility test was done using water, hexane and ethanol as solvents; and soil degradation under controlled conditions. Bioplastic film thicknesses measured 0.41 mm and 0.43 mm for G. salicornia and H. opuntia, respectively. The solubility test shows that both samples are soluble in water but insoluble in ethanol and hexane. The bioplastics were slightly acidic at pH 6.89–6.9 and demonstrated complete biodegradation within three days in soil when exposed to water. UV-Vis, FTIR and SEM analyses confirmed successful incorporation of ZnONps. These properties underscore the potential of seaweed-based bioplastics with ZnONps for sustainable applications in packaging, agriculture, and biomedical fields.