Collagen is widely used in drugs, biomaterials, foods, and cosmetics. By-products of the fishing industry are rich sources of collagen, which can be used as an alternative to collagen traditionally harvested from land mammals. 

However, commercial applications of fish-based collagen are limited by the low efficiency, low productivity, and low sustainability of the extraction process. This study applied a new technique (electrodialysis) for the extraction of Takifugu flavidus skin collagen.

We found electrodialysis to have better economic and environmental outcomes than traditional dialysis as it significantly reduced the purification time and wastewater (~95%) while maintaining high extraction yield (67.3 ± 1.3 g/100 g dry weight, p < 0.05).

SDS-PAGE, amino acid composition analysis, and spectrophotometric characterization indicated that electrodialysis treatment retained the physicochemical properties of T. flavidus collagen.

Heavy metals and tetrodotoxin analyses indicated the safety of T. flavidus collagen. Notably, the collagen had similar thermal stability to calf skin collagen, with the maximum transition temperature and a denaturation temperature of 41.8 ± 0.35 and 28.4 ± 2.5 °C, respectively.

All evidence suggests that electrodialysis is a promising technique for extracting collagen in the fishing industry and that T. flavidus skin collagen could serve as an alternative source of collagen to meet the increasing demand from consumers.

Fish skin collagen

The study, for the first time, introduced electrodialysis for the extraction of fish skin collagen (T. flavidus). This cost-effective technique was found to be superior to traditional dialysis with its advanced efficiency (2 h/trial), large capacity (100 L/trial), high extraction yield (67.3 ± 1.3 g/100 g DW), and better environmental sustainability (6 L wastewater/L sample).

SDS-PAGE, amino acid composition analysis, and spectrophotometric characterization demonstrated that T. flavidus collagen extracted by electrodialysis primarily consisted of type I collagen with a purity of 96.1 ± 1.3%.

ICP-MS analysis demonstrated that the heavy metals of T. flavidus collagen were less than the Chinese national standards. ELISA analysis indicated the safety of T. flavidus collagen.

Notably, the collagen appeared to have better thermal stability than other fish species, with Tmax and Td of 41.8 ± 0.35 and 28.4 ± 2.5 °C, respectively. This observation can be attributed to its relative higher imino acid content (246 ± 0.04 residues/1000 amino acid residues).

Cell proliferation experiment demonstrated that the cell proliferation rates of the experimental groups were slightly higher than those of the negative control group, but there was no significant difference. In addition, both NaCl level and pH condition were found to affect the relative solubility of T. flavidus collagen.

All evidence suggests that electrodialysis is a promising technique for fish collagen and that T. flavidus skin collagen could serve as an alternative source of collagen to meet the increasing demand from academia and industry.