Influencia del hidrolizado de proteínas en el comportamiento bioproductivo en gallinas de la línea L1 White Leghorn / Influence of protein hydrolysates on bioproduction performance in L1 line White Leghorn hens

RESUMEN El objetivo de la presente investigación fue evaluar la influencia del hidrolizado de proteínas (HP) como suplemento nutricional en el comportamiento bioproductivo en gallinas White Leghorn. Se utilizaron gallinas de reproductores ligeros con 39 semanas de edad, durante seis semanas. Se realizó un diseño completamente aleatorizado con dos tratamientos de 320 gallinas cada uno (tres réplicas de 40 gallinas). El T1, recibió diariamente 2 mL de HP por ave y al T2, no se le ofertó el producto. Se controlaron las variables bioproductivas (producción total de huevos, porcentaje de postura, consumo total de pienso, conversión, viabilidad y la mortalidad por causas), los indicadores de la incubación (huevos a planta, los porcentajes de incubación, incubabilidad y pollitos de primera) y los de calidad (consumo de pienso por pollito de primera y pollitos de primera por gallina). Se observaron diferencias significativas en el porcentaje de postura y significativa para la conversión masal y en los huevos a planta, porcentaje de incubación y porcentaje de incubabilidad y con mejor comportamiento en los indicadores de calidad en las gallinas que recibieron HP. Se concluye que el empleo de HP mejora el porcentaje de postura y la conversión masal y los indicadores relativos a la incubación, porcentaje de huevos aptos a planta, porcentaje de incubación y de incubabilidad de gallinas de la línea ligera, adicionalmente, su uso reduce aproximadamente en 100 gramos el consumo de pienso necesario para obtener un pollito de primera.

ABSTRACT The objective of this study was to evaluate the influence of protein hydrolysates (PH), as a nutritional supplement, in the bioproduction performance of White Leghorn hens. Thirty-nine-week old light line hens were assessed during six weeks. Two treatments (T) were designed involving 320 hens each (three replications of 40 hens each). In T1, each bird received 2 ml of PH daily; the birds in T2 were not offered the product. The following variables were controlled: bioproduction (total egg production, egg-laying percentage, total feed intake, mass conversion, viability, and caused mortality); incubation indicators (eggs to plant, incubation percentage, hatchability, and top quality chicks) and; quality (feed intake by top quality chicks, and top quality chicks per hen). The hens that received the PH showed significant differences in the laying, incubation, and hatchability percentage, as well as mass conversion, and the egg to plant ratio. They showed better performance in quality indicators. It is concluded that the use of PH in light line hens improves their bioproduction performance, as well as the indicators of to incubation, egg to plant ratio, and hatchability; its use also reduces by approximately 100 grams the necessary food intake to obtain top quality chicks.

Fructo-oligosaccharides production by the Gluconacetobacter diazotrophicus levansucrase expressed in the methylotrophic yeast Pichia pastoris.

Levansucrase (LsdA) (EC 2.4.1.10) from Gluconacetobacter diazotrophicus (formerly Acetobacter diazotrophicus) yields high levels of fructo-oligosaccharides (FOS) from sucrose. A DNA fragment encoding the precursor LsdA lacking the first 57 amino acids was fused to the pho1 signal sequence under the control of the Pichia pastoris-alcohol oxidase 1 (AOX1) promoter. Methanol induction of a P. pastoris strain harboring a single copy of the lsdA expression cassette integrated in the genome resulted in the production of active levansucrase. After fermentation of the recombinant yeast, LsdA activity was detected in the periplasmic fraction (81%) and in the culture supernatant (18%) with an overall yield of 1% of total protein. The recombinant LsdA was glycosylated and displayed optimal pH and temperature for enzyme activity similar to those of the native enzyme, but thermal stability was increased. Neither fructosylpolymerase activity nor FOS production was affected. Incubation of recombinant LsdA in sucrose (500 g l(-1)) yielded 43% (w/w) of total sugar as 1-kestose, with a conversion efficiency about 70%. Intact recombinant yeast cells also converted sucrose to FOS although for a 30% efficiency.

Substitution of Asp-309 by Asn in the Arg-Asp-Pro (RDP) motif of Acetobacter diazotrophicus levansucrase affects sucrose hydrolysis, but not enzyme specificity.

beta-Fructofuranosidases share a conserved aspartic acid-containing motif (Arg-Asp-Pro; RDP) which is absent from alpha-glucopyranosidases. The role of Asp-309 located in the RDP motif of levansucrase (EC 2.4.1.10) from Acetobacter diazotrophicus SRT4 was studied by site-directed mutagenesis. Substitution of Asp-309 by Asn did not affect enzyme secretion. The kcat of the mutant levansucrase was reduced 75-fold, but its Km was similar to that of the wild-type enzyme, indicating that Asp-309 plays a major role in catalysis. The two levansucrases showed optimal activity at pH 5.0 and yielded similar product profiles. Thus the mutation D309N affected the efficiency of sucrose hydrolysis, but not the enzyme specificity. Since the RDP motif is present in a conserved position in fructosyltransferases, invertases, levanases, inulinases and sucrose-6-phosphate hydrolases, it is likely to have a common functional role in beta-fructofuranosidases.

Expression in Escherichia coli of the lpdA gene, protein sequence analysis and immunological characterization of the P64k protein from Neisseria meningitidis.

By making use of recombinant DNA technology it is possible to characterize meningococcal outer membrane proteins (OMPs) capable of stimulating a host immune response. The lpdA gene, which codes for an OMP (P64k) from Neisseria meningitidis, was cloned in Escherichia coli. The recombinant protein was recognized by sera from patients convalescing from meningococcal disease. The monoclonal antibodies obtained against the recombinant protein recognized the natural protein on a Western blot, and monoclonal antibody 114 was assayed in ELISA with a panel of 85 N. meningitidis strains. The protein was recognized in 81 strains (95.3%); the strains that were not recognized were neither epidemic nor isolated from systemic disease. The complete amino acid sequence of P64k was obtained by automatic sequencing and MS.

Effect of the position of a basic amino acid on C-terminal rearrangement of protonated peptides upon collision-induced dissociation.

Internal rearrangement involving the loss of the C-terminal amino acid residue upon collision-induced dissociation (CID) or metastable decomposition was studied for protonated peptides. To investigate the structural characteristics of peptides responsible for this rearrangement, a series of synthetic peptides were prepared and subjected to B/E-linked scan or tandem mass spectrometric analyses using a four-sector instrument. The results showed that the position of a basic amino acid in the peptide sequence and its basicity have a significant influence on the rearrangement. Arginine (Arg) located at the n-1 position facilitates the rearrangement with about twice as many rearrangement ions as is observed for the other Arg-containing peptides. This can be attributed to the interaction of a positively charged guanidino group of Arg with its own carbonyl group via a salt bridge which is tightly formed in vacuo between a guanidino and carboxylate groups, the mechanism of which is analogous to that previously proposed for the formation of similar rearrangement ions observed in the spectra of metal-cationized peptides. This association would result in the facile attack of the C-terminal hydroxyl group on the penultimate carbonyl group, leading to the rearrangement. In addition, the rearrangement ion was observed both in metastable decomposition and high-energy CID spectra obtained by B/E-linked scan analyses without or with gas, respectively, but in a sequence dependent manner.