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Optimal usage of urea-based fertilizers can increase their use efficiency and reduce pollution. A new alternative for prolonged-release (PR) urea based on wheat-gluten (WG) membranes obtained by electrospinning was studied. The effect of pH and temperature on the release rate of urea and its transport mechanisms were evaluated. At pH 4, 7, and 10, the equilibration times obtained were 1, 3, and 5 h, respectively. Additionally, at a higher temperature, a larger amount of urea was released into the medium. The Ritger–Peppas model suggests that with pH 4 and pH 10, at 25 °C, there is an anomalous diffusion mechanism. On the other hand, the remainder of the release conditions tested showed a release mechanism of urea by simple diffusion. According to the results, a potential application of these wheat-gluten membranes on the release system of urea for soils with pH 7 and soil temperatures between 25 and 40 °C is proposed.

The chemical structure, thermal denaturation and nanostructure of collagen, obtained from a cation-exchange separation of the mantle, fins and tentacles of jumbo squid (Dosidicus gigas), were comparatively studied. The main idea of this work, was to provide an in-depth understanding of the interdependence between pyridinoline (Pyr) content, helix chemical structure and nanostructure of squid collagen with squid tissue firmness. The tentacles required more shear force and its collagen presented the higher temperature and enthalpy of transition, than the mantle and fins. The tentacle firmness may be explained by the relatively higher imino amino acid content, proline and lysine hydroxylation degrees and Pyr content of its collagen. Moreover, among the regions studied, the collagen from the tentacles had a more intense β band chain. Also, the Fourier transform infrared analysis and Raman spectra, implied that the collagen in the tentacles, was more intermolecularly ordered than the mantle and fins. Consistent with these results, a comparative evaluation of the surface morphology of the three regions, with atomic force microscopy, suggested a more ordered collagen structure in the tentacles (lower roughness values). Based on the above, collagen from tentacles has a higher degree of molecular order that sustains a higher muscle firmness compared to that of other anatomical regions.

Chitosan films (CF) [1 and 2% w/v] alone and with cinnamaldehyde (CNE) [0.25, 0.5 and 1% v/v] were prepared using an emulsion method, and the obtained films were characterized in terms of water vapor permeability (WVP), water solubility and optical, mechanical and antioxidant properties. The incorporation of CNE at 1% (v/v) significantly decreased the water solubility of the film by approximately 4% for the 1 and 2% CF films, whereas the WVP increased (2.5–3.5 times). The incorporation of CNE (0.25 and 0.5%) into 2% CF significantly increased the tensile strength (TS) (62 and 34%, respectively) and the percent elongation (%E) values, 26, 30 and 52% for CF that contained 0.25, 0.5 and 1% CNE, respectively. The largest value of the elasticity modulus (EM) was observed for 2% CF with 0.25% CNE. All films exhibited a yellow appearance (b*), but the CNE content had a marked impact on the coloration of the films. The CNE recoveries of the CF films (1 and 2%) with 1% of CNE were high (43 and 67%). The antioxidant activities indicated that the incorporation of 1% CNE into CF films (1 and 2%) increased the antioxidant activity. The protective effects of the films with and without CNE on erythrocytes were very strong (36–72% hemolysis inhibition). These results suggest there are potential applications for CF-CNE films as active packaging for the preservation of food products.

Chymotrypsin was purified from jumbo squid hepatopancreas (HP) with 2.4-fold and yield 1.9%, and characterized with a molecular weight of 31 kDa, as estimated by sodium dodecyl sulfatepolyacrylamide gel electrophoresis (SDS-PAGE). Chymotrypsin effect over collagen extracted from the mantle, fins and arms of the jumbo squid was evaluated. The enzyme exhibited the maximum activity at pH 7 and 65°C using Suc-Ala-Ala-Pro-Phe-p-nitroanilide (SAAPNA) as a substrate and it was identified using the specific inhibitors N-tosyl-L-phenylalaninechloromethyl ketone (TPCK) and phenyl methyl sulfonyl fluoride (PMSF), showing residual activities of 6% and 0%, respectively. Furthermore, high activity was observed in the pH range of 4.0 to 8.0. Purified enzyme showed a moderate in vitro activity using muscle collagen as a substrate. Although further research is needed, the results suggest that the enzyme has a potential application where acidic or slightly alkaline conditions are needed.

The physicochemical characteristics of protein hydrolysates of jumbo squid (Dosidicus gigas) byproducts (JSBP) produced by endogenous proteases at two different pH values (5.0 and 7.0) were studied using destructive and nondestructive methods. Reaction mixture samples were collected at different interval times during hydrolysis to monitor changes in the level of hydrolysis (DH) using the OPA method, the protein peptide molecular masses (MM), and SDS-PAGE. The DH increased from 3.5 to 11.2 % at pH 5.0 and from 4.8 to 17.5 % at pH 7.0. Both pH treatments exhibited similar degradation patterns with progressive proteolysis and, after 120 min of hydrolysis, yielded hydrolysates that contained MM

Myofibrillar protein are the principally responsible of gelling properties in fishery resource, hence, during protein concentrate or isolated proteins preparation, sarcoplasmic protein are discarded; however, myofibrillar protein can support low levels of sarcoplasmic proteins without affecting the gelling property. Therefore, the aim of this study was to gradually remove sarcoplasmic proteins from giant squid mantle by means of different ionic strengths (I). Solutions of NaCl with different ionic strengths (I=0.0, 0.1, and 0.3) were used to obtain 3 protein concentrates. The electrophoretic profile in SDS-PAGE showed differences in protein removal with a high solubility of mantle proteins. The texture profile analysis showed that hardness increased in mantle protein washed with higher I. The total reactive sulfhydryls showed significant changes (p

Vermiculated sailfin catfish (Pterygoplichthys disjunctivus, Weber, 1991), a member of the Loricariidae family and an invasive species of several inland waters around the world, possess an enormous digestive tract representing about 10% of fish weight. Thus, the aim of this study was to partially characterize proteases from their digestive tracts. Azocasein digestion of the crude extract of intestine at different pH values and temperatures revealed the presence of alkaline proteases with optimum activities at pH 9.0 and 50°C. Incubation assays of the crude extract with inhibitors such as phenyl methyl sulfonyl fluoride, N-α-p-tosyl-l-lysine chloromethyl ketone, N-tosyl-phenyalanine chloromethyl ketone, benzamidine, pepstatin A and ethylenediamine tetra-acetic acid showed that trypsin and chymotrypsin are the main alkaline proteinases present. Zymography showed that the crude extract of Pterygoplichthysdisjunctivus viscera contained proteases with molecular masses ranging from 21.5 to 116 kDa. Trypsin and chymotrypsin were inhibited by the following ions in decreasing order: Hg2+, Fe2+, Cu2+, Li+, Mg2+, K+, while Mn2+, and Ca2+ had no effect. Activities decreased continuously as the NaCl concentration increased from 0 to 30%. These results constitute important background information for future studies and for the potential biotechnological use of the crude digestive extract from this invasive species.