The aim of this study was to increase the antibacterial spectrum of modified hen egg white lysozyme (HEWL) with thermal and chemical treatments against Gram-negative bacteria. The antibacterial activity of heat-denatured HEWL and chemical denatured HEWL against Gram-negative and Gram-positive bacteria was evaluated in 15 h of incubation tests. HEWL was denatured by heating at pH 6.0 and pH 7.0 and chemical denaturing was carried out for 1.0, 1.5, 2.0, and 4.0 h with DL-Dithiothreitol (DTT). HEWL modified by thermal and chemical treatments was characterized using the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) electrophoresis method. Heat-denatured HEWL lytic activity against Micrococcus lysodeikticus lessened with increasing temperature and time of incubation with the chemical agent (DTT). The loss of lytic activity in modified HEWL suggests that the mechanism of action of the antibacterial activity is not dependent on the lytic activity. Thermal and chemical treatments of HEWL enabled the production of oligoforms and increased antibacterial activity over a wider spectrum. Heat-denatured HEWL at pH 6.0 and chemically-denatured HEWL increased the HEWL antibacterial spectrum against Gram-negative bacteria (Escherichia coli ATCC 25922). HEWL at 120 °C and pH 6.0 (1.0 mg/mL) inhibited 78.20% of the growth of E. coli. HEWL/DTT treatment for 4.0 h (1.0 mg/mL) inhibited 68.75% of the growth E. coli. Heat-denatured HEWL at pH 6.0 and pH 7.0 and chemically-denatured HEWL (1.0, 1.5, 2.0, and 4.0 h with DTT) were active against Gram-positive bacteria (Staphylococcus carnosus CECT 4491T). Heat-denatured and chemical-denatured HEWL caused the death of the bacteria with the destruction of the cell wall. LIVE/DEAD assays of fluorescent dye stain of the membrane cell showed membrane perturbation of bacteria after incubation with modified HEWL. The cell wall destruction was viewed using electron microscopy. The results obtained in this study suggest that heat-denatured HEWL at pH 6.0 and chemical-denatured HEWL treatments increase the HEWL antibacterial activity against Gram-negative bacteria.

ResumenEl objetivo del presente trabajo fue determinar el rendimiento reproductivo de hembras de C. caementarius mantenidas con alimento natural. Se empleó 24 hembras inmaduras (5,2 cm y 2,0 g), acondicionadas en ocho acuarios (45 L) y alimentadas durante dos meses de acuerdo a cada tratamiento, con pota (Dosidicus sp.), almeja (Semele solida), poliqueto (Pseudonereis sp.) y con alimento balanceado. El rendimiento reproductivo de las hembras fue mejorado cuando se alimentó con poliqueto y pota, lográndose la maduración entre 16 y 18 días con alta fecundidad (2627 y 1377 huevos g -1 ) y fertilidad (2566 y 1364 larvas g -1 , respectivamente).Palabras Claves: Camarón, Cryphiops caementarius, nutrición, reproducción. AbstractThe aim was to determine the reproductive performance of females of C. caementarius maintained with natural food. Twenty four females inmature were used (5,2 cm and 2,0 g), conditioned in eight aquarium (50 l) and fed during two months according to each treatment, with giant squid (Dosidicus sp), clam (Semele solid), polychaete (Pseudonereis sp.) and with balanced. The reproductive performance of females was improved when fed with polychaete and giant squid, achieving maturation between 16 to 18 days with higher fecundity (2627 and 1378 eggs g -1 ) and fertility (2566 and 1364 larvae g -1 , respectively).

Efecto de dietas con ensilado biológico de residuos de molusco en el crecimiento del camarón Cryphiops caementarius y tilapia Oreochromis niloticus en cocultivo intensivo Effect of diets with biological silage of mollusk residues on the growth of shrimp Cryphiops caementarius and tilapia Oreochromis niloticus in intensive co-culture

Efecto de dietas con lecitina de soya en el crecimiento, muda y supervivencia de machos del camarón de río Cryphiops caementarius (Crustacea: Palaemonidae) Effect of diets with soy lecithin on the growth, molting and survival of males of the river shrimp Cryphiops caementarius (Crustacea: Palaemonidae

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