Francisco Javier Castillo-Yáñez

Shrimp oncoprotein nm23 is a functional nucleoside diphosphate kinase

Biosynthesis of nucleoside triphosphates is critical for bioenergetics and nucleic acid replication, and this is achieved by nucleoside diphosphate kinase (NDK). As an emerging biological model and the global importance of shrimp culture, we have addressed the study of the Pacific whiteleg shrimp (Litopenaeus vannamei) NDK. We demonstrated its activity and affinity towards deoxynucleoside diphosphates. Also, the quaternary structure obtained by gel filtration chromatography showed that shrimp NDK is a trimer. Affinity was in the micro-molar range for dADP, dGDP, dTDP and except for dCDP, which presented no detectable interaction by isothermal titration calorimetry, as described previously for Plasmodium falciparum NDK. This information is particularly important, as this enzyme could be used to test nucleotide analogs that can block white spot syndrome virus (WSSV) viral replication and to study its bioenergetics role during hypoxia and fasting.

Identification of T‐cell stimulating antigens from Giardia lamblia by using Giardia‐specific T‐cell hybridomas

T‐cell immune response plays an important role in controlling Giardia lamblia infections. Little is known about the G. lamblia‐specific antigens that stimulate a cell‐mediated immune response. The aim of the present study was to identify T‐cell stimulating G. lamblia antigens. For this purpose, we generated a group of Giardia‐specific T‐cell hybridomas (2F9, 4D5, 6D10, 8B9, 9B10, 10F7 and 10G5). Hybridomas were screened for reactivity with G. lamblia protein extract by the CTLL bioassay. These T‐cell hybridomas did not exhibit any significant activation either in the absence of G. lamblia protein extract or in the presence of irrelevant antigen (hen white egg lysozyme). To further characterize the T‐cell hybridomas generated, we selected three hybridomas (10G5, 4D5 and 9B10). Giardia lamblia proteins of 90–110, 65–77 and 40–64 kDa showed T‐cell stimulating activity for the hybridomas 10G5, 4D5 and 9B10, respectively, in a concentration‐dependent manner. Protein extract obtained from different G. lamblia strains (GS/M‐83‐H7, WB C6 and a clinical isolate (YJJ)) stimulated all T‐cell hybridomas, indicating that T‐cell‐stimulating antigens are expressed among different G. lamblia strains. In conclusion, we identified T‐cell stimulating G. lamblia antigens by using Giardia‐specific T‐cell hybridomas. To our knowledge, these hybridomas are the first‐described T‐cell hybridomas specific for G. lamblia.

Biochemical, Physical, Chemical, and Microbiological Assessment of Blue Shrimp (Litopenaeus stylirostris) Stored in Ice

Postmortem changes in blue shrimp (Litopenaeus stylirostris) muscle were studied on the basis of biochemical, chemical, physical, and microbiological changes during an 18 day storage period at 0°C. Adenosine 5′-triphosphate (ATP) content, breakdown products, K-value, pH, trimethylamine nitrogen (TMA-N), total volatile basic nitrogen (TVB-N), water holding capacity (WHC), color, and texture (shear force) changes were examined. Also, total mesophilic and psychrophilic bacterial counts were measured. K-value increased linearly (r2 = 0.98) from an initial value of 1.37 ± 0.59 to 59.42 ± 6.05% at Day 18. Spoilage indicators TVB-N and TMA-N increased from 29.56 ± 1.33 and 0.69 ± 0.25 to 39.04 and 2.04 ± 0.59 mg of N/100 g at Day 18, respectively; meanwhile, the total viable counts of mesophilic and psychrophilic bacteria increased from 3.48 ± 0.44 and 2.61 ± 0.29 log CFU/g to 6.27 ± 0.21 and 7.14 ± 0.39 log CFU/g, respectively, which indicated spoilage at the end of the storage period. The pH, texture, WHC, and color were affected (p < 0.05) during the storage period. Overall, results indicate that blue shrimp muscle quality was maintained for 12 days of storage in ice.

Preparation and characterization of films made of poly(l-lactic acid)/poly(l-lactic acid) grafted maleic anhydride/epigallocatechin gallate blends for antibacterial food packaging

The antimicrobial activity of films made of poly(l-lactic acid)/poly(l-lactic acid) grafted maleic anhydride(copolymer)/epigallocatechin gallate(EGCG) blend was determined. The effect of epigallocatechin gallate incorporation (0.03, 0.5, 5, and 10 wt%) as a natural antibacterial was determined by direct contact, solid and liquid culture media. The film antimicrobial activity was evaluated against two bacteria (gram-negative: Pseudomonas spp.; gram-positive: Staphylococcus aureus). The copolymer was prepared and characterized by Fourier transform infrared analysis and Molau test. Furthermore, the degree of grafting was determined. The epigallocatechin gallate migration profile through the films were determined and the minimum epigallocatechin gallate concentration in films required to show antibacterial activity was evaluated. The results showed that only the films with 10 wt% epigallocatechin gallate significantly affected (p < 0.05) the cell morphology and inhibited the growth of S. aureus (56% with copolymer and 55% inhibition without copolymer) and Pseudomonas spp. (28% inhibition, with and without copolymer). Incorporating copolymer inhibited the growth of Pseudomonas spp. and induced morphological changes in S. aureus. The diffusion coefficient was dependent on the presence of copolymer, which increased the epigallocatechin gallate release rate. Incorporating epigallocatechin gallate and copolymer modified the film properties. Fourier transform infrared analysis indicated hydrogen bonds which were attributed to the interaction between copolymer and epigallocatechin gallate. The results demonstrate the potential application of poly(l-lactic acid) (biodegradable polymer) and copolymers in active packaging, as well as the importance of incorporating epigallocatechin gallate as a natural antibacterial agent.

Engineering and antibacterial properties of low-density polyethylene films with incorporated epigallocatechin gallate

The antibacterial activity of low-density polyethylene/adhesive resin (10%)/epigallocatechin gallate (0.03, 0.5, 5, and 10%) extrusion cast films were evaluated against Staphylococcus aureus (gram positive) and Pseudomonas sp. (gram negative) via direct contact and in solid and liquid culture media. The epigallocatechin gallate concentration in the active films was established per the in vitro antibacterial analysis of pure epigallocatechin gallate against S. aureus and Pseudomonas sp. The epigallocatechin gallate migration profile and concentration required to inhibit bacterial growth in broth were determined. In addition, the effects of epigallocatechin gallate and adhesive resin on the mechanical, color, and thermal film properties were investigated. The results indicate that pure epigallocatechin gallate inhibited the growth of both bacteria. However, only the films with 10 wt% epigallocatechin gallate (with and without adhesive resin) induced morphological changes and inhibited the growth of S. aureus (p < 0.05). In addition, the films with 10 wt% epigallocatechin gallate (with adhesive resin) induced morphological changes in Pseudomonas sp. (p < 0.05). The adhesive resin increased the epigallocatechin gallate release rate in the migration profile (p < 0.05). The epigallocatechin gallate and adhesive resin modified the film properties (p < 0.05). Fourier transform infrared analysis indicated hydrogen bonds between the adhesive resin and epigallocatechin gallate. This study demonstrated that epigallocatechin gallate is a potential antibacterial agent and that adhesive resin provides advantages to active films.

Optimal Immobilization of Acidic Proteases from Monterey Sardine (Sardinops sagax caeurelea) on Partially Deacetylated Chitin from Shrimp Head Waste

ABSTRACT Response surface methodology was employed to optimize the immobilization yield of acidic proteases from Monterey sardine (Sardinops sagax caeurelea) using partially deacetylated chitin as immobilization support. A rotatable central composite design was applied to evaluate the effects of immobilization conditions such as enzyme loading (X1), immobilization pH (X2), and tripolyphosphate concentration (X3) on the immobilization yield. The analysis of variance revealed that the established model was significant (p < 0.05), and the adjustment of the quadratic model with the experimental data was satisfactory. Under optimal conditions (X1 = 0.05 mg/mL, X2 = 3.16, and X3 = 0.75%), an immobilization yield of 79.1% was achieved; a value that was in accordance with the predicted one.

Impact of Two Commercial In Vivo Transport Methods on Physiological Condition of the Japanese Oyster (Crassostrea gigas)

The effect of two commercial in vivo transport methods (cardboard boxes and ixtle sacks) on the physiological condition of Japanese oyster (Crassostrea gigas) was evaluated. Total carbohydrates, glycogen, adenosine 5′-triphosphate (ATP) and related products, adenylate energy charge (AEC), and pH of transported oysters in simulated conditions were determined. The results showed that the ATP initial concentration was low from the beginning of the experiment, and AEC decreased in both transport methods. With respect to the total carbohydrates and glycogen, the samples maintained in cardboard box and ixtle sack decreased during transport, respectively. Similarly, significant changes in pH were observed for both methods. Our results showed that physiologically the best in vivo transporting method for Japanese oyster is in cardboard boxes.

Partial characterization of 5′-nucleotidase from giant squid (Dosidicus gigas) mantle Caracterización parcial de la enzima 5′-nucleotidasa del manto de calamar gigante (Dosidicus gigas)

The most important cephalopod resource in the northwestern area of Mexico is the jumbo squid whose postmortem biochemical behavior has been studied in detail. Adenosine triphosphate (ATP) degradation in this organism is different than the other species because of the fast degradation of adenosine monophosphate (AMP) metabolite in mantle. In this research, AMP deaminase from jumbo squid mantle was partially characterized. The enzyme showed an optimum behavior at 50 °C, the enzyme lost more than 90% of its activity within 15 min from 55 to 60 °C, and the enzyme remained stable for 30 min from 10 to 50 °C. It was also stable within the pH range of 3.0–5.0 and exhibited an optimum activity at pH 4.5. Enzyme was strongly activated by Mg+2 and weakly activated by Ca+2. ATP was an excellent activator even in a low concentration, while adenosine diphosphate (ADP) did it at higher concentrations. These results suggest that enzyme might be regulated by the adenylate energy charge.

Protective Effect of an Edible Tomato Plant Extract/Chitosan Coating on the Quality and Shelf Life of Sierra Fish Fillets

The products of fishing are highly perishable foods. Thus, it is necessary to seek viable alternatives that help to preserve product freshness and quality and to increase its shelf life. One of these alternatives is the use of extracts with antimicrobial activity obtained from plants, such as tomato, which has been observed to present compounds with antimicrobial activity. The objective of this work was to determine the effect of an extract obtained from the tomato plant and incorporated into an edible chitosan coating on the quality and shelf life of the sierra fish fillet stored on ice for 15 days. For the latter, an extract was prepared with dehydrated tomato plants, which was incorporated by immersion alone or in combination with an edible chitosan-based coating in sierra fish fillets. The following treatments were applied: C (Chitosan), TPE (Tomato Plant Extract), TPE-C (TPE-Chitosan), and control (without chitosan and extract). Color, pH, WHC, ATP-related compounds, and value were monitored during 15 days of storage on ice. Likewise, the total count of mesophiles was determined. The results indicated that treatments C, TPE, and TPE-C were significantly different ( ) from lot control in terms of the concentration of ATP-related compounds, value, pH, and total mesophilic count. We concluded that application of the extract alone or in combination with chitosan allows for the improvement of the quality and shelf life of the sierra fish fillet.