γ-Irradiation on shrimp waste: Effects on fermentation using L. plantarum for obtaining high purity α-chitin, and efficiency on biominerals recovery

The effects of γ-irradiation on fermentation efficiency using Lactobacillus plantarum were assessed as part of bioprocess to produce high-purity chitin. Valuable biominerals such as calcite and hydroxyapatite were recovered. Two approaches were compared: (i) γ-irradiated and (ii) non-irradiated shrimp waste samples. In both methods, 500 g of shrimp waste, 7% (w/v) inoculum, and 10 % (w/w) sucrose were used, incubating at 30 °C. The purification procedure involved treatment with 0.4 M NaOH and 0.6 M HCl. Biominerals in the liquid phase were analyzed by thermogravimetry, and soluble protein was quantified using the bicinchoninic acid assay. SEM-EDS analysis was conducted to examine morphology, elemental composition, and mineral distribution. Crystalline phases were quantified by X-ray diffraction, including amorphous content, crystallinity index, and α-chitin crystal domain size. The crystalline phases detected included α-chitin, hydroxyapatite [Ca₅(PO₄)₃OH], calcite [CaCO₃], and portlandite [Ca(OH)₂]. FT-IR spectroscopy confirmed the presence of α-chitin, phosphate, and carbonate groups. TG-DSC analysis revealed that irradiated samples exhibited slightly lower thermal stability than non-irradiated ones. Regarding chitin purity, both treatments yielded 0 % residual mass, while commercial chitin presented 1.47 %, indicating higher purity in the treated samples. Significant differences in pH, fermentation time, and soluble protein content were observed between irradiated and non-irradiated samples.