Valorization of shrimp waste: Chitosan extraction, formulation, and antimicrobial assessment of a novel antiseptic mouth spray

• Chitosan from shrimp waste shows activity against oral bacteria. • Excel model revealed antagonism among mouth spray ingredients. • CI analysis showed antagonism with chitosan and peppermint oil or ethanol. • Combined Effect Score estimates antimicrobial activity of formulas. • Shrimp waste chitosan offers a sustainable option to combat halitosis. This study explored the use of chitosan, extracted from shrimp waste, as a sustainable antimicrobial agent in antiseptic mouth spray formulations for combating halitosis. A modified chemical method yielded chitosan with specific compositional characteristics (16.43% yield). FTIR confirmed successful chitosan conversion from shrimp shell biowaste, with mineral and protein removal, chitin deacetylation, and polysaccharide preservation. The extracted chitosan demonstrated antimicrobial activity against oral bacteria, showing inhibitory zones ranging from 8.5 mm to 10.1 mm at chitosan concentrations of 10 to 30 mg/mL. An Excel-based formulation model using Combination Index (CI) analysis identified potential antagonistic interactions between chitosan and common mouth spray ingredients, such as peppermint oil and ethanol. The model calculated a Combined Effect Score (CES) to estimate overall antimicrobial activity. These findings suggest that shrimp waste-derived chitosan is a promising sustainable alternative for addressing halitosis. However, careful formulation optimization is crucial to minimize potential antagonistic interactions. This study contributes to waste valorization, promotes sustainable practices, and advances oral health. It supports healthier communities, reduces marine pollution, fosters local economic growth, drives bio-based innovation, enables sustainable production, and advances climate action.