Utilizing mussel and shrimp shell waste for chitin and chitosan extraction: a pathway to eco-friendly bioplastics

In this study, chitin and chitosan were obtained from freshwater mussel Unio mancus shells for the first time. In addition, chitin and chitosan were also produced from the shells of deep-water rose shrimp Parapenaeus longirostris. In another stage of the study, biodegradable bioplastics were synthesized using starch isolated from red macroalgae and chitosan extracted from shell waste. The extracted chitin and chitosan were characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction (XRD). The degree of deacetylation (DD), ash content, fat binding capacity (FBC) and water binding capacity (WBC) were also analyzed. Based on dry weight, 42.28% chitin and 74.81% chitosan were obtained from mussel shells and 39.57% chitin and 65.73% chitosan were obtained from shrimp shells. The ash content of chitin and chitosan ranged between 1.74–2.01%, while the degree of deacetylation of chitosan was 80.51% and 80.28%, for mussel and shrimp shells, respectively. FTIR and XRD analyses identified functional groups specific to chitin and chitosan and confirmed the presence of α-chitin structure. SEM analysis showed that chitin has a smooth and regular plate-like structure, while chitosan has an irregular, rough and nanoporous fibrous structure. The bioplastics tested in moist soil exhibited 28.2–88.1% biodegradation within 20 days. These results demonstrate the potential of chitin and chitosan produced from freshwater mussel shell waste to be effectively utilized for bioplastic production. Furthermore, these biopolymers have the potential to replace commercial sources.