The rising demand for sustainable alternatives to petroleum-based plastics is driving the development of biodegradable packaging materials made from innovative protein sources. Post-maltodextrin-extracted broken rice (PMEBR), an abundant agro-industrial by-product, is a promising alternative protein substrate but remains underutilized. This study investigated the extraction, structural modification, and valorization of PMEBR protein to create biodegradable films, supported initially by advanced analytical characterization and machine-learning-based formulation optimization. Rice protein concentrates were produced using alkali solubilization-acid precipitation (control protein concentrate, CPC) and enzyme-assisted extraction with phytase and xylanase (enzymatic protein concentrate, EPC). EPC showed higher protein purity (87%) than CPC (58%) and the raw material (54%). Structural and thermal analyses, including FTIR, XRD, DSC, TGA, LC-MS intact mass, FESEM, and CLSM, revealed that enzymatic treatment increased crystallinity, decreased random-coil structures, and improved thermal stability of protein concentrates. EPC had the highest glass transition temperature (73.62 °C) and residual mass at 600 °C, indicating better resistance to thermal degradation. Biodegradable protein films were prepared using EPC as the protein source and varying protein levels (4-12%) with dual plasticizers (glycerol and sorbitol). Film properties, such as tensile strength, elongation, moisture content, thickness, solubility, and swelling index, were assessed. A comprehensive machine-learning pipeline that included outlier removal (IQR), RobustScaler normalization, and training nine regression models identified the Decision Tree as the most accurate predictor of film properties (R ² = 0.98). Multi-objective desirability optimization predicted an optimal composition of 12% protein, 5% glycerol, and 50% sorbitol, which exhibited high tensile strength, low solubility, and excellent dimensional stability among 655 samples (133 x 5). Further, crosslinking with 5% formaldehyde, protein aggregation at 90 °C for 4 hours at pH 10, and microwave treatment at 300 W for 180 seconds have produced films with superior mechanical and barrier properties. The biodegradable tests and other migration and enzymatic tests were also conducted, further confirming their biodegradability. This method provides a scalable and sustainable way to convert agricultural waste streams into value-added packaging materials, supporting circular bioeconomy principles and increasing the role of alternative proteins in food-related applications.