Temperature effects on type I pepsin-solubilised collagen extraction from silver-line grunt skin and its in vitro fibril self-assembly

Abstract

Fish skin is a potential source of collagen. Increasing the extraction temperature increases the yield of collagen. However, it may also result in degradation of the peptide chains, thus damaging the 3D structure of collagen that is vital for its application as a biomaterial. This work investigated the effects of extraction temperature on the yield and characteristics, including fibril self-assembly, of type I pepsin-solubilised fish skin collagen. Pepsin-solubilised collagens were extracted from fresh skin of silver-line grunt at 4, 10, 20 and 28 °C for 6 h. Extraction at 10 °C gave the highest yield of collagens (439.32 ± 96.43 mg g(-1) fresh skin, dry basis), which were identified as type I and comprised β, α1 and α2 subunits. Extraction at higher temperatures (20 and 28 °C) resulted in the formation of low-molecular-weight peptide fragments, thus reducing the yield of the resultant type I collagen. The denaturation temperatures of collagens extracted at 4 and 10 °C, as determined by thermal analysis using differential scanning calorimetry, were 39.5 and 37.5 °C respectively. In vitro fibril self-assembly of 1 mg mL(-1) collagen solution (pH 6) incubated at 25 °C was only observed with collagens extracted at 4 and 10 °C. The 10 °C collagen not only showed a higher rate of self-assembly, but its matrix also had a larger fibril diameter of 0.50 ± 0.07 µm (compared with 0.41 ± 0.07 µm for the 4 °C collagen) after 4 h of incubation. The results indicated strong effects of extraction temperature on the yield and characteristics of the collagen obtained. Extraction of pepsin-solubilised collagen from silver-line grunt skin at 4-10 °C gave a high yield of type I collagen with molecular integrity suitable for tissue-engineering applications.