In this study, Lactiplantibacillus plantarum HAN99, isolated from sediment samples collected along the Alexandria Mediterranean Seacoast in Egypt, was evaluated for its ability to produce polysaccharides. To optimize polysaccharide production, statistical techniques were used, and the extracted polysaccharides were purified for further characterization. High-Performance Liquid Chromatography (HPLC) analysis identified glucose and galactose as the primary components of the polysaccharide. These polysaccharides were then loaded onto chitosan-based nanoparticles, which were characterized using Fourier Transform-Infrared Spectroscopy (FT-IR) and scanning electron microscopy (SEM). The study further investigated the potential agricultural applications of the polysaccharide-loaded nanoparticles by assessing their effects on plant growth. The results revealed that the nanoparticles enhanced the growth of Mentha (mint) leaves, reducing leaf loss compared to the control group. Additionally, the EPS chitosan-based nanoparticles exhibited strong antioxidant activity, as demonstrated by a DPPH assay (∼75.6-80.3%). These findings highlight the potential of microbial polysaccharides as sustainable, eco-friendly alternatives for agricultural enhancement and the development of green agricultural practices.