RESUMEN

Sargassum spp. is a biomass that can potentially use as an alternative for bioethanol production. Hydrothermal processes (liquid hot water and steam explosion pretreatment) were carried out at different operational conditions. Enzymatic hydrolysis performed a preliminary test with different ratios 1:1 and 1:2 (cellulases and hemicellulases) of enzyme loading, once selected 1:2 ratio was obtained conversion yield of 99.91% and therefore carried a scale-up in stirred bioreactor getting 95.92% saccharification yield. Pre-simultaneous saccharification and fermentation strategy was performed in a continuous stirred tank bioreactor (CSTBR), producing ethanol yield of 57.69%, and for simultaneous saccharification and fermentation strategy was performed in a bubble column reactor was 71.37% ethanol yield. The energy efficiency was analyzed in different scenarios; the best data was 30.19 (gsugar/MJ) in the bioreactor enzymatic hydrolysis process. This development allows for establishing the conditions for a third-generation biorefinery on a circular bioeconomy using Sargassum biomass.

Asunto(s)

Sargassum , Algas Marinas , Vapor , Biomasa , Agua , Hidrólisis , Fermentación , Etanol , Biocombustibles

RESUMEN

Armchair graphene nanoribbons, when forming a superlattice, can be classified into different topological phases, with or without edge states. By means of tight-binding and classical molecular dynamics (MD) simulations, we studied the electronic and mechanical properties of some of these superlattices. MD shows that fracture in modulated superlattices is brittle, as for unmodulated ribbons, and occurs at the thinner regions, with staggered superlattices achieving a larger fracture strain than inline superlattices. We found a general mechanism to induce a topological transition with strain, related to the electronic properties of each segment of the superlattice, and by studying the sublattice polarization we were able to characterize the transition and the response of these states to the strain. For the cases studied in detail here, the topological transition occurred at ∼3-5% strain, well below the fracture strain. The topological states of the superlattice - if present - are robust to strain even close to fracture. The topological transition was characterized by means of the sublattice polarization of the states.

RESUMEN

Chlamydia pecorum, an obligate intracellular bacterium, is associated with reproductive and systemic diseases in sheep, goats, pigs, cattle, and koalas. The main conditions include polyarthritis, conjunctivitis, enteritis, pneumonia, encephalomyelitis, orchitis, placentitis, and abortion. Even though there are several studies showing that C. pecorum infections are widely spread in the world, in Mexico there are no reports. During 2016, as part of a sheep restocking program in Mexico, sheep were imported from New Zealand. Briefly after their arrival in the herds in the State of Mexico, these sheep presented abortions during the last third of gestation. A total of 62 sheep vaginal swabs that had presented abortion from different municipalities of the State of Mexico were collected. Bacterial isolation was performed using L929 mouse fibroblasts, and molecular identification was achieved by 23S rRNA (Chlamydiaceae family) and ompA gene (species-specific) real-time polymerase chain reaction (PCR). In addition, the 16S rRNA subunit and ompA gene were amplified and sequenced. Seven of 62 samples were positive for C. pecorum by bacterial isolation, 23S rRNA, and ompA gene real-time PCR. The 16S rRNA subunit and ompA gene amplicons were purified and the nucleotide sequence was determined in both directions. The consensus sequences homology search was performed using BLASTn analysis and showed a 100% of homology with the C. pecorum 16S rRNA subunit and 99% with the C. pecorum ompA gene. The population structure analyses using ompA gene demonstrated 15 genetic populations or clusters of 198 sequences from GenBank and our sequences were in a particular genetic structure corresponding to genotype "O." Herein, we describe the presence of C. pecorum in sheep imported from New Zealand into Mexico. Genetic analysis of the ompA gene showed that the isolates belong to genotype O and are related to strains isolated from sheep, cattle, and koalas.

Asunto(s)

Infecciones por Chlamydia , Phascolarctidae , Enfermedades de las Ovejas , Animales , Bovinos , Chlamydia , Infecciones por Chlamydia/epidemiología , Infecciones por Chlamydia/microbiología , Infecciones por Chlamydia/veterinaria , Femenino , Variación Genética , Masculino , México/epidemiología , Ratones , Phascolarctidae/microbiología , Embarazo , ARN Ribosómico 16S/genética , ARN Ribosómico 23S , Ovinos , Enfermedades de las Ovejas/microbiología , Porcinos

RESUMEN

Sargassum spp is an invasive macroalgae and an alternative feedstock for bioethanol production. Sargassum spp biomass was subjected to high-pressure technology for biomass fractionation under different operating conditions of temperature and residence time to obtain glucan enriched pretreated solids (32.22 g/100 g of raw material). Enzyme hydrolysis process at high pretreated solid loading (13%, w/v) and enzyme loading of 10 FPU/g of glucan was performed, obtaining 43.01 g/L of glucose corresponding to a conversion yield of 92.12%. Finally, a pre-simultaneous saccharification and fermentation strategy (PSSF) was performed to produce bioethanol. This operational strategy produced 45.66 g/L of glucose in the pre-saccharification stage, and 18.14 g/L of bioethanol was produced with a glucose to bioethanol conversion yield of 76.23%. The development of this process highlights the feasibility of bioethanol production from macroalgal biomass in the biorefinery concept.

Asunto(s)

Sargassum , Biocombustibles , Biomasa , Etanol , Fermentación , Hidrólisis , Tecnología

RESUMEN

There are many simulation studies of mechanical properties of graphene nanoribbons (GNR), but there is a lack of agreement regarding elastic and plastic behavior. In this paper we aim to analyze mechanical properties of finite-size GNR, including elastic modulus and fracture, as a function of ribbon size. We present classical molecular dynamics simulations for three different empirical potentials which are often used for graphene simulations: AIREBO, REBO-scr and REAXFF. Ribbons with and without H-passivation at the borders are considered, and the effects of strain rate and different boundaries are also explored. We focus on zig-zag GNR, but also include some armchair GNR examples. Results are strongly dependent on the empirical potential employed. Elastic modulus under uniaxial tension can depend on ribbon size, unlike predictions from continuum-scale models and from some atomistic simulations, and fracture strain and progress vary significantly amongst the simulated potentials. Because of that, we have also carried out quasi-static ab-initio simulations for a selected size, and find that the fracture process is not sudden, instead the wave function changes from Blöch states to a strong interaction between localized waves, which decreases continuously with distance. All potentials show good agreement with DFT in the linear elastic regime, but only the REBO-scr potential shows reasonable agreement with DFT both in the nonlinear elastic and fracture regimes. This would allow more reliable simulations of GNRs and GNR-based nanostructures, to help interpreting experimental results and for future technological applications.

RESUMEN

Forty-two enrofloxacin-resistant Escherichia coli strains isolated from eggs and first-week mortality associated with yolk sac infection of two vertically integrated poultry companies of Central Mexico in 1997 and 2005 were characterised. E. coli resistance to 19 antibiotics was determined, as well as the minimum inhibitory concentrations (broth dilution) for ciprofloxacin. The presence of gyrA,B, parC,E chromosomal point mutations, qnrA,B,S plasmid genes and the aminoglycoside acetyltransferase aac(6')-Ib-cr were determined by PCR and sequencing. Resistance to ampicillin (95%), piperacillin (95%), gatifloxacin (95%), levofloxacin (95%), ampicillin/sulbactam (90%), cefazolin (85%), trimethoprim/sulfamethoxazole (80%), amoxicillin/clavulanic acid (80%), aztreonam (80%), cefepime (80%), cefotaxime (80%), ceftazidime (80%), ceftriaxone (80%) and cefoxitin (75%) was high in the 2005 strains and 19 (95%) strains were resistant to 7 or more antimicrobials. The strains from 1997 expressed high rates of resistance only to the fluoroquinolones and 4 strains (18%) expressed resistance to 7 or more antimicrobials. All strains had a gyrA mutation (Ser83Leu) and a parC mutation (Ser80Ile or Ser80Arg) and 41 (97.6%) strains had a second gyrA mutation (Asp87Asn, Asp87Tyr or Asp87Gly). Only two (4.7%) strains had a parE mutation (Ser458Ala). A total of 10 strains were positive for the aac(6')-Ib wild-type gene, 6 strains for the aac(6')-Ib-cr variant and 6 strains possessed both the wild type and the variant. No gyrB mutations or qnrA,B,S genes were detected. This is the first report in Latin America of chromosomal and plasmid quinolone resistance genes in E. coli strains recovered from poultry.

Asunto(s)

Antibacterianos/farmacología , Farmacorresistencia Bacteriana , Infecciones por Escherichia coli/veterinaria , Fluoroquinolonas/farmacología , Enfermedades de las Aves de Corral/microbiología , Animales , Escherichia coli/efectos de los fármacos , Infecciones por Escherichia coli/microbiología , México , Pruebas de Sensibilidad Microbiana/veterinaria , Óvulo/microbiología , Aves de Corral

RESUMEN

The current method for goat brucellosis diagnosis is based on the World Organization for Animal Health (OIE) using the screening card test (CT), with antigen at 8% (CT8) or 3% (CT3) of cell concentrations, and the confirmatory complement fixation test (CFT). However, these tests do not differentiate antibodies induced by vaccination from those derived from field infections by Brucella species or other bacterial agents; in places like Mexico, where the prevalence of brucellosis and the vaccination rates are high, there is a considerable percentage of false positive reactions that causes significant unnecessary slaughter of animals. Furthermore, results of the fluorescence polarization assay (FPA) using the Brucella abortus O-polysaccharide (OPS) tracer in goats are poorer than those with cattle. The present study was undertaken to investigate a tracer prepared from the native hapten (NH) of the Rev. 1 strain of Brucella melitensis to improve FPA performance on goat brucellosis diagnosis. Evaluation of 48 positive samples and 96 negative samples showed that the NH tracer was more accurate (p<0.01) than the OPS tracer (97.2% vs. 93.8% accuracy, respectively). On the diagnostic performance evaluation, the NH tracer performed better (87.5% accuracy, 79.5% sensitivity, 84.3% specificity, and 163.8 performance index) than the OPS tracer (83.5%, 75.9%, 81.0%, and 156.9, respectively) using 1009 positive and 2039 negative Mexican field goat sera samples selected by test series approved by the OIE (card test 3% and CFT). We demonstrated a new application for the NH lipopolysaccharide on detecting antibodies against Brucella using the FPA, which may yield faster results (minutes vs. 24-72h) than the immunodiagnosis assays frequently used in bovine brucellosis. In addition, NH tracer produces similar or better performance results than the conventional OPS tracer, using the FPA in goat sera samples.

Asunto(s)

Anticuerpos Antibacterianos/sangre , Brucella melitensis/inmunología , Brucelosis/veterinaria , Inmunoensayo de Polarización Fluorescente/veterinaria , Enfermedades de las Cabras/microbiología , Haptenos/química , Animales , Anticuerpos Antibacterianos/inmunología , Brucella abortus/inmunología , Brucella melitensis/química , Brucelosis/diagnóstico , Brucelosis/inmunología , Brucelosis/microbiología , Bovinos , Fluoresceína-5-Isotiocianato/química , Inmunoensayo de Polarización Fluorescente/métodos , Colorantes Fluorescentes/química , Enfermedades de las Cabras/sangre , Enfermedades de las Cabras/diagnóstico , Enfermedades de las Cabras/inmunología , Cabras , Haptenos/inmunología , Curva ROC , Reproducibilidad de los Resultados , Sensibilidad y Especificidad

RESUMEN

The aim of this study was to evaluate the effect of 3 Brucella ovis subcellular protein fractions: Outer membrane (OMP), inner membrane (IMP), and cytoplasm (CP), on cellular immune response by in vitro production of interleukin (IL)-2, IL-4, and interferon (IFN)-gamma. Each fraction was inoculated 3 times into Balb/c mice, primary cultures of mice spleen cells were done, and these were then stimulated with the fractions. Culture supernatants were collected at 24, 48, 72, 96, and 120 h postinoculation. Cytokine concentration was measured by Duoset-enzyme-linked immunosorbent assay (ELISA). The OMP fraction induced highest cellular immune response of 1000 pg/mL of IL-2 at 24 h, which decreased to < 100 pg/mL by 96 h. The IL-2 response for the IMP fraction was low at 24 h, but exceeded that of the OMP fraction at 72, 96, and 120 h. The CP showed a poor IL response. Regarding the IFN-gamma production, OMP and IMP induced a high response at 120 h. These results open the possibility for the use of B. ovis outer and inner membrane proteins as a subcellular vaccine.

Asunto(s)

Proteínas Bacterianas/inmunología , Brucella ovis/inmunología , Interferón gamma/biosíntesis , Interleucina-2/biosíntesis , Interleucina-4/biosíntesis , Animales , Antígenos Bacterianos/inmunología , Proteínas de la Membrana Bacteriana Externa/inmunología , Citoplasma/inmunología , Electroforesis en Gel de Poliacrilamida/veterinaria , Ensayo de Inmunoadsorción Enzimática/veterinaria , Hipersensibilidad Tardía/veterinaria , Masculino , Ratones , Ratones Endogámicos BALB C , Factores de Tiempo

RESUMEN

The protection conferred by the reduced-dose Rev 1 Brucella melitensis vaccine in goats that had been immunized 5 years previously was evaluated. Sixteen goats vaccinated 5 years before with Rev 1 (1 x 10(5) cfu) and 5 non-vaccinated goats were challenged with B. melitensis 16M (4 x 10(5) cfu) using the conjunctival route. After giving birth or aborting, the goats were sacrificed and tissue samples were taken for bacteriological study. The challenge strain was recovered in 12%, of the animals from the vaccinated group, and in (80% of the control group. It is concluded, therefore that the use of reduced-dose Rev 1 protects goats vaccinated in endemic areas for at least 5 years after immunization.

Asunto(s)

Vacuna contra la Brucelosis/administración & dosificación , Brucella melitensis/inmunología , Brucelosis/veterinaria , Enfermedades de las Cabras/prevención & control , Animales , Vacuna contra la Brucelosis/inmunología , Brucelosis/prevención & control , Recuento de Colonia Microbiana/veterinaria , Conjuntiva , Relación Dosis-Respuesta Inmunológica , Femenino , Cabras , Factores de Tiempo

RESUMEN

OBJECTIVE: To assess the presence of Yersinia enterocolitica in otherwise healthy pigs slaughtered for human consumption. METHODS: One hundred pharyngeal tonsils were sampled in a slaughterhouse in the state of Mexico. The minimum sample size (n=100) was calculated based on a preliminary sample of 20 cases, which had 20% positive cases. The collected tonsil samples were inoculated in Rappaport broth, and Salmonella-Shigella and McConkey media. The biotyping identification process was based on biochemical and serological tests using O:3, O:8 and O:9 antisera. RESULTS: Twenty-two isolates were obtained. Most were biotype 1 (8 cases of O:3 and 8 cases of O:9), but 6 cases could not be serotyped. None of the isolates were of O:8 group. CONCLUSIONS: This was the first time that Y. enterocolitica serotypes were isolated from pig tonsils in Mexico. Its importance rely on the fact that the isolated serotypes are the most commonly found in public health problems.

Asunto(s)

Técnicas de Tipificación Bacteriana , Microbiología de Alimentos , Carne/microbiología , Yersinia enterocolitica/clasificación , Animales , Estudios Transversales , Serotipificación , Porcinos/microbiología , Yersinia enterocolitica/aislamiento & purificación

RESUMEN

The objective of this study was to determine if B. abortus rough mutant strains RB51 and rfbK are eliminated in goat milk. Thirty milk goats were divided into two groups. Group I was inoculated with 4x10(10) cfu/ml of B.abortus RB51 strain and Group II with 1x10(9) cfu/ml of B. abortus rfbK strain by subcutaneous route in the right axilary region. Milk samples were taken aseptically on a daily basis for the first 30 days and weekly for the second and third months. The samples were inoculated on Farrell's media and incubated under 5-10% CO(2) at 37 degrees C for 10 days. The suspicious colonies were recultured in Farrell's media. There were no isolations of bacteria with characteristics of Brucella from any of the milk samples collected during 90 days of the study. It was concluded that neither of the strains used at these doses were eliminated by milk in goats inoculated during lactation.

Asunto(s)

Vacunas Bacterianas/inmunología , Brucella abortus/inmunología , Animales , Brucella abortus/aislamiento & purificación , Cabras , Leche/microbiología , Mutación , Vacunación

RESUMEN

A group of 35 healthy adult goats ranging from two to six years old were bought from a chlamydiosis and brucellosis-free flock; they were vaccinated against Brucella melitensis with Rev1 vaccine at reduced doses, and one month later placed in isolation units. The animals were one month pregnant at the moment of purchase, and during the third month of pregnancy 10 out of the 35 dams aborted. Necropsy of the aborted fetus and examination of the foetal membranes was performed where no macroscopic lesions were observed. Abomasal liquid, foetal lung and liver, and placenta samples were taken for bacteriological analysis while sera from the goats that aborted was collected for serological investigation. Chlamydia psittaci was isolated in all cases, while no Brucella was detected. All sera reacted positive to anti-Chlamydia antibodies by the indirect immunofluorescence test. This represents the first report of Chlamydia psittaci isolation from cases of goat abortion in Mexico.

Asunto(s)

Aborto Veterinario/microbiología , Infecciones por Chlamydia/veterinaria , Chlamydophila psittaci/aislamiento & purificación , Enfermedades de las Cabras/microbiología , Aborto Veterinario/epidemiología , Animales , Anticuerpos Antibacterianos/sangre , Infecciones por Chlamydia/epidemiología , Infecciones por Chlamydia/microbiología , Chlamydophila psittaci/inmunología , Brotes de Enfermedades , Femenino , Feto/microbiología , Técnica del Anticuerpo Fluorescente Indirecta , Cabras , México/epidemiología , Embarazo

RESUMEN

A hot saline extract of Brucella ovis strain REO 198 at a concentration of 5 micrograms/ml in phosphate buffer pH 7.2 was used to adsorb onto Maxisorb plates and incubated at 37 degrees C during 12 h; unadsorbed excess antigen was washed off thrice with phosphate buffer containing 0.5% Tween 20. As blocking agent 1% skim milk was used. The conjugate used was protein G bound to peroxidase diluted 1:100. Thirty three sheep sera from bacteriologically confirmed infected animals and 39 sheep sera from healthy animals from disease-free zones were used. Sera were diluted 1:200. ELISA's sensitivity was 97% and specificity 84%. The cut-off value was chosen for a high sensitivity (100%) despite some loss of specificity in order to diminish false negative results rendering thus a suitable screening test for sheep epididimitis caused by Brucella ovis.

Asunto(s)

Anticuerpos Antibacterianos/sangre , Brucella/inmunología , Brucelosis/veterinaria , Ensayo de Inmunoadsorción Enzimática , Epididimitis/veterinaria , Tamizaje Masivo/veterinaria , Enfermedades de las Ovejas/diagnóstico , Animales , Brucelosis/diagnóstico , Brucelosis/inmunología , Epididimitis/diagnóstico , Epididimitis/inmunología , Epididimitis/microbiología , Masculino , Sensibilidad y Especificidad , Ovinos , Enfermedades de las Ovejas/inmunología

RESUMEN

The separation and the simultaneous determination of beta-carotene, cantaxanthin, lutein, violaxanthin and neoxanthin was accomplished using thin-layer chromatography on Chromarods, flame ionization detection and a two-stage development technique. Data were transformed through an unweighted straight-line regression of the logarithm of peak area ratios on the logarithm of the mass ratios. The determinations are highly reproducible and all statistical estimates are highly significant. The linear concentration range for each compounds is reported. No evidence of degradation of the carotenoids during the analyses was found. Up to ten samples can be analysed simultaneously in less than 2 h.

Asunto(s)

Carotenoides/análisis , Cromatografía en Capa Delgada , Ionización de Llama , Análisis de Regresión , Solventes