Catalytic and Operational Stability of Acidic Proteases from Monterey Sardine (Sardinops sagax caerulea) Immobilized on a Partially Deacetylated Chitin Support

Protease immobilization on a novel activated carrier alginate/dextrose beads: Improved stability and catalytic activity via covalent binding

Protease from Bacillus thuringiensis strain-MA8 was successfully immobilized onto activated Alginate/dextrose (Alg/dex) beads as a new carrier with immobilization yield 77.6 %. The carrier was characterized using Scanning electron microscopy and Fourier transforms infrared spectrophotometer at every step of the immobilization process. Immobilized protease showed an increase of 10 °C in the optimum temperature compared to the free enzyme. However, the optimum pH for both the free and the Alg/dex/protease was found to be 8. The lower activation energy and deactivation rate constant and the higher half-life time and D-value confirm that the new Alg/dex carrier is suitable for promoting enzyme stability. The raise in thermal stability is also shown by the increased deactivation energy of the Alg/dex/protease compared to its free form by 1.47-fold. Likewise, the enzyme immobilization enhancement of Alg/dex/protease was accompanied by a marked increase in enthalpy and Gibbs free energy. The negative entropy for both free and Alg/dex/protease indicates that the enzyme is more stable in thermal deactivation. The Km and Vmax for the Alg/dex/protease were 2.05 and 1.22-times greater than the free form. Furthermore, Alg/dex/protease displayed good reusability as it retained 92.7 and 52.4 % of its activity after 8 and 12 hydrolysis cycles.

Sc-CO2 extraction of fish and fish by-products in the production of fish oil and enzyme

Supercritical carbon dioxide (Sc-CO2) is an alternative tool to extract lipid for the production of fish oil and enzyme from fish by-products (FBPs). In the application of Sc-CO2, this review covers sample preparation, lipid extraction operation, and characterization of fish oil and enzyme as final products. Generally, the fish samples with moisture content less than 20% and particle size less than 5 mm are considered before lipid extraction with Sc-CO2. Sc-CO2 parameters, such as pressure (P), temperature (T), extraction time (text), and flow rate (F), for simultaneous recovery of fish oil, protein, and enzyme were found to be less severe (P: 10.3-25 MPa; T: 25-45 °C, text: 20-150 min; F: 3-50 g/min) than the extraction of fish oil alone (P: 10-40 Mpa; T: 35-80 °C; text: 30-360 min; F: 1-3000 g/min). The enzyme from the Sc-CO2 defatted sample showed higher activity up to 45 U/mg due to lower denaturation of protein as compared to the organic solvent treated sample albeit both samples having similar pH (6-10) and temperature stability (20-60 °C). Overall, mild extraction of lipid from FBPs using Sc-CO2 is effective for the production of enzymes suitable in various industrial applications. Also, fish oil as a result of extraction can be produced as a health product with high polyunsaturated fatty acids (PUFAs) and low contamination of heavy metals.

Characterization of the trypsin-III from Monterey sardine (Sardinops caeruleus): Insights on the cold-adaptation from the A236N mutant

Trypsins (E.C. 3.4.21.4) are digestive enzymes that catalyze the hydrolysis of peptide bonds containing arginine and lysine residues. Some trypsins from fish species are active at temperatures just above freezing, and for that are called cold-adapted enzymes, having many biotechnological applications. In this work, we characterized a recombinant trypsin-III from Monterey sardine (Sardinops caeruleus) and studied the role of a single residue on its cold-adapted features. The A236N mutant from sardine trypsin-III showed higher activation energy for the enzyme-catalyzed reaction, it was more active at higher temperatures, and exhibited a higher thermal stability than the wild-type enzyme, suggesting a key role of this residue. The thermodynamic activation parameters revealed an increase in the activation enthalpy for the A236N mutant, suggesting the existence of more intramolecular contacts during the activation step. Molecular models for both enzymes suggest that a hydrogen-bond involving N236 may contact the C-terminal α-helix to the vicinity of the active site, thus affecting the biochemical and thermodynamic properties of the enzyme.