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

BACKGROUND: 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. RESULTS: Pepsin-solubilised collagens were extracted from fresh skin of silver-line grunt at 4, 10, 20 and 8 degrees C for 6 h. Extraction at 10 degrees 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 beta, alpha 1 and alpha 2 subunits. Extraction at higher temperatures (20 and 28 degrees 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 degrees C, as determined by thermal analysis using differential scanning calorimetry, were 39.5 and 37.5 degrees C respectively. In vitro fibril self-assembly of 1 mg mL(-1) collagen solution (pH 6) incubated at 25 degrees C was only observed with collagens extracted at 4 and 10 degrees C. The 10 degrees 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 mu m (compared with 0.41 +/- 0.07 mu m for the 4 degrees C collagen) after 4 h of incubation. CONCLUSION: 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 degrees C gave a high yield of type I collagen with molecular integrity suitable for tissue-engineering applications. (C) 2010 Society of Chemical Industry