The present investigation was aimed to develop an easy, low-cost and eco-friendly method for the synthesis of Chitosan based iron oxide Nanoparticles (Cs-FeNPs) using shells of Penaeus monodon. The synthesized Cs-FeNPs were characterized by using Ultraviolet-Visible spectroscopy (UV), Fourier-Transform Infrared spectroscopy (FT-IR), X-ray Diffraction (XRD), Transmission Electron Microscope (HR-TEM) and Scanning Electron Microscope (SEM with EDAX). The visible dark black color formation and surface plasmon resonance at 233 nm indicates the biosynthesis of Cs-FeNPs. The TEM images showed polydispersal, and spherical Cs-FeNPs particle size of 3 to 5 nm. Antibacterial activity of chitosan aqueous extract and Cs-FeNPs showed an excellent activity against Gram-positive bacteria (Staphylococcus aureus and Enterococcus faecalis) and Gram-negative bacteria (Escherichia coli, Enterobacter, Klebsiella pneumoniae and Pseudomonas aeruginosa).

Chitosan, a polysaccharide derivative of chitin forms the structural components in the exoskeletons of crustacean animals and is also found in the cell walls of fungi. Chitosan is produced primarily from the crab shell waste through chemical means. The chemical structure of chitosan has been identified and characterized by FT-IR and XRD. In the current study, the antimicrobial activity of chemically deacetylated chitosan extracts of mud crabs (Scylla serrata) was evaluated against five human pathogenic isolates viz. Staphylococcus aureus, Salmonella typhi, Klebsiella pneumonia, Bacillus cereus and Pseudomonas aeruginosa using agar disc diffusion method. These were performed to determine the crystallinity and functional properties of chitosan. The results showed that the antibacterial effect increased with increasing chitosan concentration. This study showed that chitosan isolated from crab shell has potential antibacterial activity therefore it can be utilized in the food and pharmaceutical industries, and that antibacterial activity may be due to functional groups present in the crab shell.