Isolation and characterization of acid-soluble collagen from the scales of marine fishes from Japan and Vietnam

Acid-soluble collagen (ASC) was successfully extracted from the scales of lizard fish (Saurida spp.) and horse mackerel (Trachurus japonicus) from Japan and Vietnam and grey mullet (Mugil cephalis), flying fish (Cypselurus melanurus) and yellowback seabream (Dentex tumifrons) from Japan. ASC yields were about 0.43–1.5% (on a dry weight basis), depending on the species. The SDS–PAGE profile showed that the ASCs were type I collagens, and consisted of two different α chains, α1 and α2, as well as a β component. ASC of horse mackerel from Vietnam contained a higher imino acid level than that from Japan. ASC denaturation temperature (Td) ranged from 26 to 29 °C, depending on fish species and imino acid content (p < 0.01). Maximal solubility of individual collagens was observed at pHs 1–3. Collagen solubility decreased sharply at NaCl concentrations >0.4 M, regardless of fish type.