Carboxymethyl Chitosan with High Degree of Substitution: Synthesis, Optimization, Characterization, and Antibacterial Activity

ABSTRACT: Products derived from shrimp constitute 7.2 lakh tonnes of frozen shrimp exported during 2022–2023, positioning them as the largest contributors to India's total seafood exports in both quantity and value. This volume accounts for nearly 45% of the total exports for the specified period (MPEDA, 2023). In India, the organized shrimp processing sector generates a significant amount of waste, potentially representing 40–60% of the total weight of the shrimp. This substantial waste output can be transformed into a valuable biopolymer, chitosan, sourced from marine crustaceans’ exoskeletons, particularly from shrimp, through demineralization, deproteination, and deacetylation processes. The shell of the shrimp Fenneropenaeus indicus was harvested and processed to yield chitosan with a Degree of Deacetylation (DD) of 79%. Chitosan was subsequently treated with sodium hydroxide (NaOH) and monochloroacetic acid in various concentrations at multiple temperature levels and time intervals to determine the optimal formulation for producing Carboxy Methyl Chitosan (CMCS). The ideal conditions for CMCS production were identified as a concentration of 60% sodium hydroxide (NaOH) and 40% concentration of monochloroacetic acid (MCA) at 60°C for 2 hrs. The Degree of Substitution (DS) for CMCS exceeded 50% across all samples and was characterized using FTIR spectroscopy and solubility tests. The antibacterial properties of CS and CMCS are evaluated against Staphylococcus aureus and Pseudomonas aeruginosa, demonstrating sensitivity.