Enzymatic extraction and characterisation of a thermostable collagen from swim bladder of rohu (Labeo rohita)

The fish swim bladder is considered as a potential source of realistic collagen. Currently, processing of the Indian major carp rohu (Labeo rohita) generates an enormous quantity of non-edible by-products, including swim bladders, which are discarded as waste with no commercial value. In the present study, collagen was prepared from rohu swim bladder and its physicochemical and fibril-forming capacities were assessed.The collagen isolated from rohu swim bladder was characterised as type I, containing α1 and α2 chains with triple helical structure by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, fourier transform infrared spectroscopy and amino acid analysis. The extracted collagen denaturation temperature was found to be 42.16 °C by differential scanning calorimetry analysis and also exhibited a high solubility in the presence of low NaCl concentrations (0-0.6 mol L-1 ). The extracted collagen exhibited a high fibril-formation capacity at a NaCl concentration of 1.5 mol L-1 . Examination of the microstructure of collagen by scanning electron microscopy (SEM) showed a porous, sheet-like film and a multilayered structure. The fibril formation capacity of collagen was also confirmed using SEM analysis.The rohu swim bladder type I collagen was successfully extracted using an enzymatic method with a yield of 465.2 g kg-1 (dry weight basis) and was characterised as a well maintained triple helical structure. The extracted collagen exhibited a high fibril-forming ability. The results of the present study confirm that utilisation of rohu swim bladder will open up a new avenue for the better disposal of by-products and also help to minimise environmental pollution issues. © 2016 Society of Chemical Industry.