Proteinases from the Liver of Albacore Tuna (T hunnus Alalunga ): Optimum Extractant and Biochemical Characteristics

Tuna sidestream valorization: a circular blue bioeconomy approach

Tuna is an economically significant seafood, harvested throughout the world, and is heavily traded due to its high nutritional quality and consumer acceptance. Tuna meat is rich in essential nutrients such as amino acids, polyunsaturated fatty acids (PUFA), and trace minerals. The huge volume of solid and liquid sidestreams generated during the processing stages of tuna is creating environmental and socioeconomic challenges in coastal areas. Different products such as fish meal, protein hydrolysates, collagen, enzymes, oil, and bone powder can be produced from tuna sidestreams. Using different nutrient recovery technologies like enzymatic hydrolysis, chemical processing, and green technologies, various categories of product value chains can be created in line with the conventional processing industry. This review attempts to provide a route map for the tuna industry for achieving the circular blue-bioeconomic objectives and reorient the irregular utilization pattern into a sustainable and inclusive path.

Two trypsin isoforms from albacore tuna (Thunnus alalunga) liver: Purification and physicochemical and biochemical characterization

Two trypsins (A and B) from the liver of albacore tuna (Thunnus alalunga) were purified to homogeneity using a series of column chromatographies including Sephacryl S-200, Sephadex G-50 and Diethylaminoethyl-cellulose. Purity was increased to 80.35- and 101.23-fold with approximately 3.1 and 19.2% yield for trypsins A and B, respectively. The molecular weights of trypsins A and B were estimated to be 21 and 24kDa, respectively, by SDS-PAGE and size exclusion chromatography. Both trypsins showed only one band on native-PAGE. Trypsins A and B exhibited the maximal activity at 60°C and 55°C, respectively, and had the same optimal pH at 8.5 using N^α-p-Tosyl-l-arginine methyl ester hydrochloride (TAME) as a substrate. Stabilities of both trypsins were well maintained at a temperature up to 50°C and in the pH range of 7.0-11.0 and were highly dependent on the presence of calcium ion. The inhibition test demonstrated strong inhibition by soybean trypsin inhibitor and TLCK. Activity of both trypsins continuously decreased with increasing NaCl concentration (0-30%). The N-terminal amino acid sequence of 20 residues of the two trypsin isoforms had homology when compared to those of other fish trypsins.

Enzymatic hydrolysis of starry triggerfish (Abalistes stellaris) muscle using liver proteinase from albacore tuna (Thunnus alalunga)

Proteinases from liver extract from albacore tuna (Thunnus alalunga) were used to produce protein hydrolysate from starry triggerfish (Abalistes stellaris) muscle. Hydrolysis conditions for preparing protein hydrolysate from starry triggerfish muscle were optimized. Enzyme level, reaction time and fish muscle/buffer ratio significantly affected the hydrolysis (p < 0.05). Optimum conditions for triggerfish muscle hydrolysis were 5.5 % liver extract, 40 min reaction time and fish muscle/buffer ratio of 1:3 (w/v). The freeze-dried protein hydrolysate was characterized with respect to chemical composition, amino acid composition and color. The product contained 91.73 % protein, 2.04 % lipid and 6.48 % ash. The protein hydrolysate exhibited high amount of essential amino acids (45.62 %). It was light yellow in color (L (*) = 82.94, a (*) = 0.84, b (*) = 22.83). The results indicate that the extract from liver of albacore tuna could be used to produce fish protein hydrolysate and protein hydrolysate from starry triggerfish muscle may potentially serve as a good source of desirable peptide and amino acids.