Cold plasma-assisted processing: A sustainable route to high-quality chitosan from crab shells

Traditional chitosan production, involving chitin extraction and deacetylation, relies on harsh high-alkali chemical processing, which raises safety and sustainability concerns. This study proposes an atmospheric-pressure plasma pretreatment strategy to enhance deacetylation efficiency and structural quality during the alkaline deacetylation of chitin extracted from crab shells to produce chitosan. Comprehensive characterisation using Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy and molecular weight analysis reveal that plasma selectively etches the amorphous domains and weakens glycosidic linkages, thereby improving mass-transfer efficiency during deacetylation. Under 40-50% NaOH, plasma-treated samples achieve markedly higher deacetylation degrees (PAW post-processing: 65-74%) than those of the conventional method (traditional chemical method: 58-67%), together with higher crystallinity (up to 31.18%) and enhanced thermal stability. These molecular and interfacial modifications collectively enhance antibacterial performance, enlarging inhibition zones against Staphylococcus aureus and Pseudomonas aeruginosa to 14.57 ± 0.45 mm and 14.16 ± 0.06 mm, respectively. Overall, plasma pretreatment is an environmentally benign and structurally beneficial approach for producing high-performance chitosan from crab shells.