Biotechnological Aspects and Mathematical Modeling of the Biodegradation of Plastics under Controlled Conditions.

The strong environmental impact caused by plastic pollution has led research to address studies from different perspectives. The mathematical modeling of the biodegradation kinetics of solid materials is a major challenge since there are many influential variables in the process and there is interdependence of microorganisms with internal and external factors. In addition, as solid substrates that are highly hydrophobic, mass transfer limitations condition degradation rates. Some mathematical models have been postulated in order to understand the biodegradation of plastics in natural environments such as oceans. However, if tangible and optimizable solutions are to be found, it is necessary to study the biodegradation process under controlled conditions, such as using bioreactors and composting systems. This review summarizes the biochemical fundamentals of the main plastics (both petrochemical and biological origins) involved in biodegradation processes and combines them with the main mathematical equations and models proposed to date. The different biodegradation studies of plastics under controlled conditions are addressed, analyzing the influencing factors, assumptions, model developments, and correlations with laboratory-scale results. It is hoped that this review will provide a comprehensive overview of the process and will serve as a reference for future studies, combining practical experimental work and bioprocess modeling systems.

eNOS-dependent S-nitrosylation of the NF-κB subunit p65 has neuroprotective effects.

Cell death by glutamate excitotoxicity, mediated by N-methyl-D-aspartate (NMDA) receptors, negatively impacts brain function, including but not limited to hippocampal neurons. The NF-κB transcription factor (composed mainly of p65/p50 subunits) contributes to neuronal death in excitotoxicity, while its inhibition should improve cell survival. Using the biotin switch method, subcellular fractionation, immunofluorescence, and luciferase reporter assays, we found that NMDA-stimulated NF-κB activity selectively in hippocampal neurons, while endothelial nitric oxide synthase (eNOS), an enzyme expressed in neurons, is involved in the S-nitrosylation of p65 and consequent NF-κB inhibition in cerebrocortical, i.e., resistant neurons. The S-nitro proteomes of cortical and hippocampal neurons revealed that different biological processes are regulated by S-nitrosylation in susceptible and resistant neurons, bringing to light that protein S-nitrosylation is a ubiquitous post-translational modification, able to influence a variety of biological processes including the homeostatic inhibition of the NF-κB transcriptional activity in cortical neurons exposed to NMDA receptor overstimulation.

Characterization of the Bacteriophage vB_VorS-PVo5 Infection on Vibrio ordalii: A Model for Phage-Bacteria Adsorption in Aquatic Environments.

A mathematical first-order difference equation was designed to predict the dynamics of the phage-bacterium adsorption process in aquatic environments, under laboratory conditions. Our model requires knowledge of bacteria and bacteriophage concentrations and the measurements of bacterial size and velocity to predict both the number of bacteriophages adsorbed onto their bacterial host and the number of infected bacteria in a given specific time. It does not require data from previously performed adhesion experiments. The predictions generated by our model were validated in laboratory. Our model was initially conceived as an estimator for the effectiveness of the inoculation of phages as antibacterial therapy for aquaculture, is also suitable for a wide range of potential applications.

Isolation and molecular characterization of Thraustochytrium strain isolated from Antarctic Peninsula and its biotechnological potential in the production of fatty acids

ABSTRACT Thraustochytrids are unicellular protists belonging to the Labyrinthulomycetes class, which are characterized by the presence of a high lipid content that could replace conventional fatty acids. They show a wide geographic distribution, however their diversity in the Antarctic Region is rather scarce. The analysis based on the complete sequence of 18S rRNA gene showed that strain 34-2 belongs to the species Thraustochytrium kinnei, with 99% identity. The total lipid profile shows a wide range of saturated fatty acids with abundance of palmitic acid (16:0), showing a range of 16.1-19.7%. On the other hand, long-chain polyunsaturated fatty acids, mainly docosahexaenoic acid and eicosapentaenoic acid are present in a range of 24-48% and 6.1-9.3%, respectively. All factors analyzed in cells (biomass, carbon consumption and lipid content) changed with variations of culture temperature (10 °C and 25 °C). The growth in glucose at a temperature of 10 °C presented the most favorable conditions to produce omega-3fatty acid. This research provides the identification and characterization of a Thraustochytrids strain, with a total lipid content that presents potential applications in the production of nutritional supplements and as well biofuels.

Isolation and molecular characterization of Thraustochytrium strain isolated from Antarctic Peninsula and its biotechnological potential in the production of fatty acids

ABSTRACT Thraustochytrids are unicellular protists belonging to the Labyrinthulomycetes class, which are characterized by the presence of a high lipid content that could replace conventional fatty acids. They show a wide geographic distribution, however their diversity in the Antarctic Region is rather scarce. The analysis based on the complete sequence of 18S rRNA gene showed that strain 34-2 belongs to the species Thraustochytrium kinnei, with 99% identity. The total lipid profile shows a wide range of saturated fatty acids with abundance of palmitic acid (16:0), showing a range of 16.1-19.7%. On the other hand, long-chain polyunsaturated fatty acids, mainly docosahexaenoic acid and eicosapentaenoic acid are present in a range of 24-48% and 6.1-9.3%, respectively. All factors analyzed in cells (biomass, carbon consumption and lipid content) changed with variations of culture temperature (10 °C and 25 °C). The growth in glucose at a temperature of 10 °C presented the most favorable conditions to produce omega-3fatty acid. This research provides the identification and characterization of a Thraustochytrids strain, with a total lipid content that presents potential applications in the production of nutritional supplements and as well biofuels.(AU)

Isolation and molecular characterization of Thraustochytrium strain isolated from Antarctic Peninsula and its biotechnological potential in the production of fatty acids.

Thraustochytrids are unicellular protists belonging to the Labyrinthulomycetes class, which are characterized by the presence of a high lipid content that could replace conventional fatty acids. They show a wide geographic distribution, however their diversity in the Antarctic Region is rather scarce. The analysis based on the complete sequence of 18S rRNA gene showed that strain 34-2 belongs to the species Thraustochytrium kinnei, with 99% identity. The total lipid profile shows a wide range of saturated fatty acids with abundance of palmitic acid (16:0), showing a range of 16.1-19.7%. On the other hand, long-chain polyunsaturated fatty acids, mainly docosahexaenoic acid and eicosapentaenoic acid are present in a range of 24-48% and 6.1-9.3%, respectively. All factors analyzed in cells (biomass, carbon consumption and lipid content) changed with variations of culture temperature (10°C and 25°C). The growth in glucose at a temperature of 10°C presented the most favorable conditions to produce omega-3fatty acid. This research provides the identification and characterization of a Thraustochytrids strain, with a total lipid content that presents potential applications in the production of nutritional supplements and as well biofuels.

Motility and chemotaxis of Pseudomonas sp. B4 towards polychlorobiphenyls and chlorobenzoates.

The polychlorinated biphenyl (PCB)-degrading Pseudomonas sp. B4 was tested for its motility and ability to sense and respond to biphenyl, its chloroderivatives and chlorobenzoates in chemotaxis assays. Pseudomonas sp. B4 was attracted to biphenyl, PCBs and benzoate in swarm plate and capillary assays. Chemotaxis towards these compounds correlated with their use as carbon and energy sources. No chemotactic effect was observed in the presence of 2- and 3-chlorobenzoates. Furthermore, a toxic effect was observed when the microorganism was exposed to 3-chlorobenzoate. A nonmotile Pseudomonas sp. B4 transformant and Burkholderia xenovorans LB400, the laboratory model strain for PCB degradation, were both capable of growing in biphenyl as the sole carbon source, but showed a clear disadvantage to access the pollutants to be degraded, compared with the highly motile Pseudomonas sp. B4, stressing the importance of motility and chemotaxis in this environmental biodegradation.

Penicillium purpurogenum produces a family 1 acetyl xylan esterase containing a carbohydrate-binding module: characterization of the protein and its gene.

At least three acetyl xylan esterases (AXE I, II and III) are secreted by Penicillium purpurogenum. This publication describes more detailed work on AXE I and its gene. AXE I binds cellulose but not xylan; it is glycosylated and inactivated by phenylmethylsulphonyl fluoride, showing that it is a serine esterase. The axe1 gene presents an open reading frame of 1278 bp, including two introns of 68 and 61 bp; it codes for a signal peptide of 31 residues and a mature protein of 351 amino acids (molecular weight 36,693). AXE I has a modular structure: a catalytic module at the amino terminus belonging to family 1 of the carbohydrate esterases, a linker rich in serines and threonines, and a family 1 carboxy terminal carbohydrate binding module (CBM). The CBM is similar to that of AXE from Trichoderma reesei, (with a family 5 catalytic module) indicating that the genes for catalytic modules and CBMs have evolved separately, and that they have been linked by gene fusion. The promoter sequence of axe1 contains several putative sequences for binding of gene expression regulators also found in other family 1 esterase gene promoters. It is proposed that AXE I and II act in succession in xylan degradation; first, xylan is attacked by AXE I and other xylanases possessing CBMs (which facilitate binding to lignocellulose), followed by other enzymes acting mainly on soluble substrates.

Adaptive responses and cellular behaviour of biphenyl-degrading bacteria toward polychlorinated biphenyls.

Polychlorinated biphenyls (PCBs) are one of the most widely distributed classes of chlorinated chemicals in the environment. For cleanup of large areas of PCB-contaminated environments, bioremediation seems to be a promising approach. However, the multitude of PCB congeners, their low bioavailability and high toxicity are important factors that affect the cleanup progression. Elucidating how the PCB-degrading microorganisms involved in the process adapt to and deal with the stressing conditions caused by this class of compounds may help to improve the bioremediation process. Also specific physiological characteristics of biphenyl-utilizing bacteria involved in the degradation of PCBs may enhance their availability to these compounds and therefore contribute to a better microbial mineralization. This review will focus in the stress responses caused in aerobic biphenyl-utilizing bacteria by PCBs and its metabolic intermediates and will also analyze bacterial properties such as motility and chemotaxis, adherence to solid surfaces, biosurfactant production and biofilm development, all properties found to enhance bacteria-pollutant interaction.

Histidine 140 plays a key role in the inhibitory modulation of the P2X4 nucleotide receptor by copper but not zinc.

To elucidate the role of extracellular histidines in the modulation of the rat P2X4 receptor by trace metals, we generated single, double, and triple histidine mutants for residues 140, 241, and 286, replacing them with alanines. cDNAs for the wild-type and receptor mutants were expressed in Xenopus laevis oocytes and in human embryonic kidney 293 cells and examined by the two electrode and patch clamp techniques, respectively. Whereas copper inhibited concentration-dependently the ATP-gated currents in the wild-type and in the single or double H241A and H286A receptor mutants, all receptors containing H140A were insensitive to copper in both cell systems. The characteristic bell-shaped concentration-response curve of zinc observed in the wild-type receptor became sigmoid in both oocytes and human embryonic kidney cells expressing the H140A mutant; in these mutants, the zinc potentiation was 2.5-4-fold larger than in the wild-type. Results with the H140T and H140R mutants further support the importance of a histidine residue at this position. We conclude that His-140 is critical for the action of copper, indicating that this histidine residue, but not His-241 or His-286, forms part of the inhibitory allosteric metal-binding site of the P2X4 receptor, which is distinct from the putative zinc facilitator binding site.

Polygraphic characterization of the sleep-epilepsy patterns in a hydranencephalic child with severe generalized seizures of the lennox-gastaut syndrome

This is the report of a hydranenecephalic child with severe generalized seizures of the Lennox-Gastaut Syndrome (LGS) who lacked the development of the entire cerebral hemispheres and had preserved the brain stem, cerebellum, hypothalamus and a portion of the thalamus as evidenced by radiological and/or physiological studies. Conventional polygraphic sleep studies in these patients showed presence of scalp EEG and other peripheral, somatic and vegetative signs characterizing the wakefulness, quiet sleep and active sleep stages. Absence of the vertex waves and disrupted sleep spindles were the major qualitative EEG abnormalities. In contrast, quantitative abnormalities in duration, latency and number of sleep cycles found in this patient were similar to those found in other children with Idiopathic Lennox-Gastaut Syndrome (ILGS). A substantial reduction in the number of interictal EEG spikes and a shortening of the ictal clonic EEG activities without concomitant EMG jerks were the most distinct epileptiform abnormalities in this child. In contrast, his basic polygraphic patterns of the tonic and apneic seizures were similar to those found in other children with ILGS. Data obtained from this child suggest that both the sleep stages and the generalized seizures of the ILGS basically depend more on the integrity of the brain stem than on the telecephalic structures

Resultados obtenidos de 105 pacientes sucesivos que ingresaron con isquemia grave que amenazaba con la pérdida de la extremidad / Results from 105 patients admitted successively with severe ischemia threatening with foot loosing

Se trata de un trabajo prospectivo, que analiza los resultados obtenidos en 105 pacientes sucesivos sin selección previa, ingresados con isquemia crónica crítica, con alto riesgo inmediato de pérdida del apoyo del pie. La edad promedio era de 68 años y 86 por ciento era de sexo masculino, las enfermedades asociadas predominantes eran las cardiorespiratorias, diabetes, vasculares encefálicas e insuficiencias renales. Los motivos de consulta fueron: dolor de reposo, necrosis o lesión ulcerada o ambos que no cicatrizaban. Todos los pacientes fueron valorados clínicamente y mediante técnicas no invasivas Doppler, eco-Doppler y fotopletismografía en el preoperatorio, complementándose con arteriografías y/o preprocedimiento. Se realizaron 10 amputaciones primarias (9,5 por ciento), 6 por imposibilidad de conservar el pie (60 por ciento), 2 por alto riesgo anestésico quirúrgico (20 por ciento) y 2 por inutilidad del miembro comprometido (20 por ciento). Se amputaron 6 pacientes a nivel de pierna, 2 con previa revascularización y 4 pacientes en muslo, no hubo complicaciones mayores, ni mortalidad. A 95 pacientes se los intentó revascularizar, en 5 (5 por ciento) no fue posible por irreconstructibilidad vascular, habiéndose explorado incluso directamente las arterias del pie. De los 90 pacientes restantes a 29 se les realizó revascularización suprainguinal (32 por ciento) y a 9 de éstos se les practicó revascularización a doble nivel supra e infrainguinal (31 por ciento). Tomaron origen en la aorta 8 puentes, en la arteria axilar 9 y 12 en la femoral común contralateral. A 61 pacientes se los revascularizó en el sector infrainguinal, el vaso receptor del puenteo más frecuentemente utilizado fue poplítea y en 20 casos (30 por ciento) fue necesario recurrir a una arteria del pie. En la cirugía suprainguinal la permeabilidad primaria fue de 96,5 por ciento secundaria de 100 por ciento, hubo 6,8 por ciento de complicaciones mayores y 3,4 por ciento de mortalidad. En este grupo se preservaron todas las extremidades. En la cirugía infrainguinal la permeabilidad primaria fue de 95 por ciento, las complicaciones mayores se presentaron en 8,1 por ciento, siendo la mortalidad de 1,6 por ciento. En este grupo se preservaron 88,5 por ciento de los pies útiles para la deambulación...

Valor de la arteriografía preoperatoria en la definición de los ejes arteriales permeables en la pierna y el pie / Value of preoperative arteriography in the definition of permeable arterial axis of leg and foot

Se tiene en cuenta que en la cirugía de salvataje de las extremidades la utilización de ejes de pierna o pie como receptores de puentes, no es infrecuente. Se analizaron los resultados de 59 aortografías por punción translumbar y 38 arteriografías por punción femoral, para definir los ejes arteriales permeables en la pierna y el pie. Esto permitió el estudio de 156 extremidades de pacientes con arteriopatía obstructiva crónica de los MMII. La aortografía muestra una PG de 28 por ciento, que no varió significativamente con o sin la existencia de lesiones ilíacas PG 36 y 24 por ciento respectivamente. La arteriografía por punción femoral tuvo una PG de 74 por ciento para definir los ejes de pierna y de 42 por ciento para los ejes del pie, lo cual lo muestra como estudio más confiable con este fin que la aortografía que tiene una PG de 28 por ciento y 8 por ciento respectivamente. Cuando el contraste de una arteriografía llega hasta el cuello del pie, la precisión de la misma para definir ejes permeables en la pierna fue de 90 por ciento para la arteria peronea, 70 por ciento para la tibial anterior y 53 por ciento para la tibial posterior. Las arterias tibiales mostraron oclusión proximal con permeabilidad distal en 50 a 54 por ciento de los casos, siendo la peronea la arteria que más frecuentemente estuvo permeable, en 90 por ciento de las veces, observándose continuidad con el eje poplíteo-tronco tibio peroneo en 74 por ciento. Teniendo en cuenta estos resultados parece aventurado decidir la indicación de irrevascularización de una extremidad, contando sólo con datos aportados por alguno de estos estudios, indefectiblemente se realizarían amputaciones mayores innecesarias, asimismo aun realizando un puente distal con dichos datos podríamos no elegir el mejor de los ejes como receptor