Collagen Extraction from Mytilus edulis Byssus By-Product: Comparison of Enzymatic and Ultrasound-Assisted Methods

The growing demand for sustainable protein sources is driving the development of marine by-product utilization. Mussel byssus, which is currently discarded during mussel processing, could be used to produce collagen-derived biomaterials. This study tested the hypothesis that ultrasound-assisted extraction could improve collagen recovery by comparing its efficiency with that of conventional pepsin-assisted extraction. The latter is time-consuming and inefficient. While conventional pepsin-assisted extraction achieved a higher collagen-derived material recovery yield (10.7%) than ultrasound-assisted extraction (5.1%), ultrasound reduced the extraction time from 72 h to just two hours. Fourier transform infrared spectroscopy (FTIR) confirmed that the characteristic amide bands were preserved in the collagen-derived material extracted using both methods. Differential scanning calorimetry (DSC) revealed thermal transitions at 59 °C for pepsin-assisted extracts and 57 °C for ultrasound-assisted extracts, indicating comparable thermal stability. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed predominantly low-molecular-weight protein fragments (<20 kDa), suggesting the presence of collagen-derived peptides rather than intact native collagen. Overall, ultrasound-assisted extraction preserved the structural and thermal characteristics of the extracted material while drastically reducing processing time. This highlights its potential as a rapid, environmentally friendly and sustainable technology for the valorization of mussel byssus within a circular bioeconomy.