Physicochemical Characterization of <i>Bombyx mori</i> Cocoon Protein Grown in the Fergana Valley

Silk proteins of Bombyx mori are important biological polymers widely used in textiles, biomaterials, and nanotechnologies due to their unique mechanical properties, biocompatibility, biodegradability, and low toxicity. However, region‐specific variations in environmental and feeding conditions may significantly influence the biochemical composition and functional properties of cocoon proteins. Therefore, the present study is aimed at providing a comprehensive biochemical and physicochemical characterization of the protein and mineral composition of B. mori cocoons grown in the Fergana Valley, addressing the lack of detailed regional data in the literature. The amino acid profile revealed the presence of 17 amino acids with a total content of 633.065 mg/g: nonessential amino acids, 396.868 mg/g (62.7%); semiessential amino acids, 133.765 mg/g (21.1%); and essential amino acids, 102.432 mg/g (16.2%). The highest concentrations were observed for serine (187.988 mg/g), aspartic acid (100.034 mg/g), cysteine (86.525 mg/g), and glycine (49.377 mg/g). The repeated fibroin motif (Gly‐Ala‐Gly‐Ala‐Gly‐Ser)n correlates with the dominance of glycine and serine, explaining the dense packing and smooth morphology of silk fibers, while elevated cysteine content indicates the role of disulfide bonds in mechanical strength. Infrared (IR) spectroscopy confirmed the proteinaceous nature of the sample, with a broad Amide A band at 3261.49 cm −1 indicating an extensive hydrogen‐bonding network and characteristic amide bands at 1642.95, 1522.16, and 1240.34 cm −1 confirming the presence of β ‐sheet‐rich secondary structures. SDS‐PAGE analysis revealed multiple protein fractions (~40, 55, 85, and 200 kDa), demonstrating the complex and heterogeneous composition of the cocoon protein system, including fibroin, sericin, and possible proteolytic fragments. Mineral analysis showed an increasing trend in total elemental content in the following sequence: mulberry leaves &lt; silkworm &lt; cocoon, with the cocoon containing 4.7 times higher mineral content than leaves. The dominant macroelements were Ca, K, and Mg, while high levels of Ca and S were characteristic of the cocoon. Among trace elements, Fe and Zn were predominant in the silkworm body, whereas Al and Si were enriched in the cocoon. The obtained results provide a scientific basis for understanding the structure–composition–property relationships of silk proteins and demonstrate that regional environmental conditions significantly influence their biochemical characteristics. From a practical perspective, these findings justify the potential use of B. mori cocoon proteins as a promising raw material for advanced biomedical applications, environmentally friendly functional materials, and value‐added silk processing technologies.

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