Environmentally conscious extraction of chitin and calcium acetate from Portunus segnis shell waste via RSM-CCD optimized acetic acid demineralization

Abstract

This study presented an environmentally conscious approach for the simultaneous extraction of chitin and calcium acetate from shells of the invasive Atlantic blue crab (Portunus segnis), an abundant marine waste in the Mediterranean Sea. The demineralization process was optimized using Response Surface Methodology (Central Composite Design) to investigate the effects of acetic acid concentration, reaction time, and solid-to-liquid ratio on residual ash content, final pH, and dry matter yield. Under optimized conditions, the demineralized chitin exhibited very low ash content (∼0.10%), confirming efficient mineral removal. The extracted chitin was obtained with a degree of acetylation of 83% and was characterized as α-chitin by FTIR (characteristic amide bands at 1622 and 1554 cm⁻¹), XRD (prominent peak at 2θ ≈ 19.8°, CrI ≈ 34%), and SEM (porous fibrillar microstructure). It displayed high water holding capacity (785%) and oil holding capacity (542%), indicating strong potential for functional applications. Calcium acetate monohydrate recovered from the filtrate was confirmed by FTIR and XRD, with an experimental yield of 42.56%. This dual-valorization strategy not only minimizes environmental impact compared to traditional strong acid methods but also introduces a zero-waste circular bioeconomy model by converting invasive species waste into two valuable bioproducts, demineralized chitin and marketable calcium acetate, in a single integrated process.