Digestive acid protease from zebra blenny (Salaria basilisca): Characteristics and application in gelatin extraction

The present study reports on the characterization and evaluation of a crude acidic protease from the viscera of zebra blenny (Salaria basilisca) for use in gelatin extraction. Using hemoglobin, zymogram analysis revealed the presence of at least one clear band. The crude acid protease was noted to be optimally active at pH 3.0 and 50 °C and highly stable over a pH range of 2.0 to 7.0. The enzymatic extract lost about 87% of its activity after incubation with pepstatin A for 30 min at 4 °C. The acidic protease from the viscera of zebra blenny was noted to be effective in the extraction of gelatin from the skin of zebra blenny, with an extraction yield of 14.65% based on the wet weight of zebra blenny skin. The extracted zebra blenny skin gelatin (ZBSG) was characterized based on its chemical composition, polypeptide pattern, gel strength, textural parameters, and functional properties. ZBSG had high protein (90.6%) and low ash (3.1%) and fat (0.6%) contents. It contained α1 and α2-chains as the major constituents and determined as belonging to type I. The bloom strength of solidified gelatin was 151.3 g. The findings from Fourier Transformed Infrared (FT-IR) spectroscopy suggested the presence of helical arrangements of ZBSG. The latter showed excellent concentration-dependent functional properties. While emulsion activity index (EAI) and emulsion stability index (ESI) decreased, foam expansion (FE) and foam stability (FS) increased as the concentration of gelatin increased. Overall, zebra blenny endogenous acid protease could open new promising opportunities for the extraction of gelatin.