Extraction optimization and characterization of collagen from the lung of soft-shelled turtle Pelodiscus sinensis

The soft-shelled turtle (Pelodiscus sinensis) is a commercially important aquatic species with abundant collagen content and precious nutritious high quality goods. The present study was to optimize the collagen extraction from lung of Pelodiscus sinensis. Single-factor test was employed to investigate the effects of different extraction methods and the major factors that influence the collagen production in enzymatic extraction method on the collagen yield of lung. Optimization of the papain enzymatic extraction parameters was then examined using an orthogonal test design L9 (3 4 ). The optimum extraction conditions were obtained when the extraction temperature, papain enzyme dose, the ratio of solid to solution, and extraction time were 32°C, 4.0mg/ml, 1:35, and 12h, respectively. Under the optimized conditions, the collagen yield was up to 79.29%. The properties of turtle lung collagen were characterized by SDS-PAGE, UV scanning, and amino acid analysis. The results showed that the extracted lung collagen had high imino acid content at 21.8% and contained two α chains, β, and γ-components, belonging to the typical type I collagen. The amphibious aquatic turtle collagen is thought to be a viable novel source for replacement of terrestrial mammals and could provide scientific reference for the development of collagen polypeptide for terrapin animals.