Application of bacterial collagenolytic proteases for the extraction of type I collagen from the skin of bigeye tuna (Thunnus obesus)

Collagen extracted from fish skin by using porcine-derived pepsin is not accepted by a large number of people due to religious constrains. The aim of the study was to explore bacterial collagenolytic proteases (CP) to extract fish skin collagen and characterize the extracted collagen. Two bacteria, Bacillus cereus FORC005 and Bacillus cereus FRCY9-2 were isolated. Glycerol and sucrose were suitable carbon sources for FORC005 and FRCY9-2, respectively. Response surface methodology (RSM) was employed to optimize pH, temperature (T) and concentration of carbon source (CC) for producing maximum CP. The temperature and pH were the most influencing factors for producing CP by FORC005 and FRCY9-2, respectively. The total yield of collagen by FORC005 and FRCY9-2 CP treatments combined with acid soluble collagen were 188 g/kg and 177 g/kg, respectively of skin (dry matter basis). The SDS-PAGE band patterns, FT-IR spectra and amino acid compositions indicated that all extracted collagens were type I collagen. The CPs produced from the bacteria were able to extract collagen from fish skin. This study provides an alternative approach for producing collagen from fish skin using CP.