Marine Waste to Nano-Wealth: Synthesis and Characterization of Chitosan Nanoparticles from Mollusca Shells with Antimicrobial Insights

This study explores the transformation of molluscan shell waste from the Nellore coast of Andhra Pradesh into highvalue chitosan nanoparticles (CNPs) using a green, biologically inspired approach. Chitin was extracted by enzymatic activity of A.niger, A. terrus and A. flavus used for deprotienization, Demineralisation and Bascillus sp used to obtain chitosan. The resulting chitosan was subjected to ionic gelation with sodium tripolyphosphate (TPP) to yield stable nanoparticles. These CNPs were thoroughly characterized using techniques including UV-Vis spectroscopy, FTIR, XRD, SEM-EDX, DLS, and zeta potential analyses. The average particle size was 112.4 ± 9.1 nm and the zeta potential measured +28.7 mV, suggesting good colloidal stability. Antimicrobial activity of the CNPs was systematically evaluated against a panel of bacterial and fungal pathogens, including Staphylococcus aureus, Escherichia coli, Candida albicans, and Aspergillus flavus. The nanoparticles demonstrated broad-spectrum efficacy with distinct zones of inhibition and low minimum inhibitory concentrations (MICs). Particularly notable was their potent bactericidal effect against Gram-positive S. aureus and significant antifungal activity against C. albicans. The antimicrobial mechanism is likely driven by electrostatic interactions with microbial membranes, leading to disruption of cellular integrity and leakage of intracellular contents. These results underscore the dual benefit of valorizing marine waste into eco-friendly nanomaterials and deploying them as effective antimicrobial agents. The study highlights the promising role of mollusca-derived chitosan nanoparticles in sustainable aquaculture management, water purification, and potential biomedical applications.