Preparation and identification of chitosan and chitosan nanoparticles from crab byproducts

This study was designed to extract chitosan from blue crab shells and prepare chitosan nanoparicles via combination of chemical extraction process with mechanical ball-milling method. The size and surface charge of the NPs were evaluated in chitosan nanoparicles using dynamic light scattering (DLS). The prepared crab chitosan and chitosan nanoparicles were evaluated for their characteristics using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Scanning Electron Microscopy coupled with Energy Dispersive X-ray analysis (SEM-EDX), Transmission Electron Microscopy (TEM) and viscosity measurements compared with commercial chitosan products. The DLS results of crab chitosan nanoparicles appeared to be the optimal chitosan nanoparicles with minimum particle size (192.74 ± 3.25 nm), zeta potential (25.15 ± 1.19 mV) smallest PDI (0.228 ± 0.011) in comparison with commercial nanoparicles had a particle size (245.47 ± 3.21 nm), zeta potential (32.24 ± 0.72 mV) smallest PDI (0.191 ± 0.055), respectively. The FTIR and XRD analyses indicated that α-chitosan mainly formed an amorphous structure along with a higher deacetylation degree. There are no diffraction peaks at 2θ ≈ 10°, showing that chitin was effectively deacetylated with a negligible content of residual chitin. Chitosan nanoparicles from crab had a particle size of about 84 nm based on Debye-Scherrer equation that is comparable to commercial nanoparticles. Crab chitosan nanoparicles has been shown to possess distinctly rough flake-like surfaces, while CS NP is compact spheres to cubes with reduced pore dimensions, as confirmed by SEM and TEM analyses. EDX with low residual mineral contents confirmed good purities of prepared materials. Rheological analysis indicated that chitosan extracted from crabs exhibited greater viscosity (31.707 to 42.849 mPa·s) than commercial chitosan (17.818 to 24.024 mPa·s), indicating a higher molecular weight and more significant intermolecular interactions. The overall chitosan yield was 11.02% of the crab shell dry weight. The findings suggest that blue crab shell waste is a value-added product. .