Off-line and on-line optical monitoring of microalgal growth.

The growth of Chlamydomonas reinhardtii microalgae cultures was successfully monitored, using classic off-line optical techniques (optical density and fluorescence) and on-line analysis of digital images. In this study, we found that the chlorophyll fluorescence ratio F 685/F 740 has a linear correlation with the logarithmic concentration of microalgae. By using digital images, the biomass concentration correlated with the luminosity of the images through an exponential equation and the length of penetration of a super luminescent blue beam (λ = 440 nm) through an inversely proportional function. The outcomes of this study are useful to monitor both research and industrial microalgae cultures.

Partial characterization of a biosurfactant extracted from Pseudomonas sp. B0406 that enhances the solubility of pesticides.

Biodegradation of some organochlorine and organophosphate pesticides is difficult because of their low solubility in water and, therefore, their low bioavailability. To overcome the hydrophobicity problem and the limited pesticide availability, biosurfactants play a major role. In this study, we evaluated the effect of an extract from Pseudomonas sp. B0406 strain with surfactant properties, on the solubility of two pesticides: endosulfan (ED) and methyl parathion (MP). Such a process was performed in order to increase the aqueous solubility of both pesticides, to increase its availability to microorganisms and to promote their biodegradation. The extract from Pseudomonas sp. B0406 showed a critical micellar concentration of 1.4 g/L and the surface tension at that point was 40.4 mN/m. The preliminary chemical and physical partial characterization of the extract with surfactant properties indicated that it is an anionic glycolipid, which increases the solubility of both pesticides of 0.41 at 0.92 mg/L for ED and of 34.58 at 48.10 mg/L for MP. The results of this study suggest the effectiveness of this extract in improving the solubility of both pesticides ED and MP in water and, therefore, of its potential use to enhance the degradation of these pesticides.

Harvesting microalgae cultures with superabsorbent polymers: desulfurization of Chlamydomonas reinhardtii for hydrogen production.

It is presented in this work a new methodology to harvest fresh water microalgae cultures by extracting the culture medium with superabsorbent polymers (SAPs). The microalgae Chlamydomonas reinhardtii were grown in the Sueoka culture medium, harvested with polyacrylic SAPs and re-suspended in the culture medium tris-acetate-potassium without sulfur (TAP-S) to generate hydrogen (H2 ) under anoxic conditions. The H2 production as an alternative fuel is relevant since this gas has high-energy recovery without involving carbon. Before microalgae harvesting, a number of range diameters (1-7 mm) for SAPs spherical particles were tested, and the initial rate (V0 ) and the maximal capacity (Qmax ) were determined for the Sueoka medium absorption. The SAP particles with the diameter range 2.0-2.5 mm performed the best and these were employed for the rest of the experiments. The Sueoka medium has a high salt content and the effect of the ionic strength was also studied for different medium concentrations (0-400%). The SAPs were reused in consecutive absorption/desorption cycles, maintaining their absorption capacity. Although the Sueoka medium reduces the SAPs absorption capacity to 40% compared with deionized water, the use of SAPs was very significant for the desulfurization process of C. reihardtii. The presence of C. reinhardtii at different concentrations does not affect the absorption capacity of the Sueoka culture medium by the SAPs. In order to reduce the time of the process, an increase of the SAPs concentration was tested, being 20 g of SAP per liter of medium, a condition to harvest the microalgae culture in 4 h. There were no evident cell ruptures during the harvesting process and the cells remained alive. Finally, the harvested biomass was re-suspended in TAP-S medium and kept under anaerobic conditions and illumination to produce H2 that was monitored by a PEM fuel cell. The use of SAPs for microalgae harvesting is a feasible non-invasive procedure to obtain high concentrations of functional biomass at low cost; it offers an attractive alternative due to its versatility and simplicity.

Discovery and characterization of a novel ATP/polyphosphate xylulokinase from a hyperthermophilic bacterium Thermotoga maritima.

Xylulokinase (XK, E.C. 2.7.1.17) is one of the key enzymes in xylose metabolism and it is essential for the activation of pentoses for the sustainable production of biocommodities from biomass sugars. The open reading frame (TM0116) from the hyperthermophilic bacterium Thermotoga maritima MSB8 encoding a putative xylulokinase were cloned and expressed in Escherichia coli BL21 Star (DE3) in the Luria-Bertani and auto-inducing high-cell-density media. The basic biochemical properties of this thermophilic XK were characterized. This XK has the optimal temperature of 85 °C. Under a suboptimal condition of 60 °C, the k cat was 83 s⁻¹, and the K(m) values for xylulose and ATP were 1.24 and 0.71 mM, respectively. We hypothesized that this XK could work on polyphosphate possibly because this ancestral thermophilic microorganism utilizes polyphosphate to regulate the Embden-Meyerhof pathway and its substrate-binding residues are somewhat similar to those of other ATP/polyphosphate-dependent kinases. This XK was found to work on low-cost polyphosphate, exhibiting 41 % of its specific activity on ATP. This first ATP/polyphosphate XK could have a great potential for xylose utilization in thermophilic ethanol-producing microorganisms and cell-free biosystems for low-cost biomanufacturing without the use of ATP.

High-yield production of dihydrogen from xylose by using a synthetic enzyme cascade in a cell-free system.

Let enzymes work: H2 was produced from xylose and water in one reactor containing 13 enzymes (red). By using a novel polyphosphate xylulokinase (XK), xylose was converted into H2 and CO2 with approaching 100 % of the theoretical yield. The findings suggest that cell-free biosystems could produce H2 from biomass xylose at low cost. Xu5P = xylulose 5-phosphate, G6P = glucose 6-phosphate.

Conocimientos, creencias y actitudes en padres mexicanos acerca del trastorno por déficit de atención con hiperactividad (TDAH) / Knowledge and beliefs in Mexican parents about attention deficit hyperactivity disorder (ADHD)

Attention deficit hyperactivity disorder (ADHD) generates controversy among the general population on its diagnosis and treatment. This could be explained by the sparse level of education about mental health, which affects the parent's knowledge and beliefs about this disorder. ADHD is highly prevalent and 3-5% of school-age children can be diagnosed. In Mexico it represents 1.5 million cases. It represents more than 30% of all cases in clinical pediatric settings. The reports in health services have shown that the time gap between symptoms identification and treatment is around 8 to 15 years. Moreover, only 25% of the affected children's parents recognize conduct or emotional problems on them and 13% receive mental health care. Attention seeking has been associated with higher severity of the disorder and parent's superior educational level. Despite the advances in the research on neurobiology and psychopharmacology, understanding of the social context that surrounds the disorder is incomplete. Comparatively little is known regarding how parents conceive the symptoms and causes of ADHD and how these parental views may relate to children's treatment. Understanding these factors is important due to the central role of parents in selecting and accessing treatments and service providers for children with ADHD. For parents and children, getting information about ADHD is a lottery that depends on which professional they see and what they read or gather from television and the Internet. Mental health professionals most give complete information to parents and children, so risks and benefits of the different treatments may be considered along with the family's needs, values and cultural background. A better understanding about the parent's knowledge, beliefs and attitudes regarding ADHD would help to improve the communication mechanisms between mental health professionals and parents during the treatment. Objective To describe the knowledge, beliefs and attitudes regarding ADHD in Mexican parents. Methods The study was approved by the local investigation review board. Informed consent was obtained and parents of children and adolescents diagnosed with ADHD were recruited at four mental health facilities (three public and one private) in two cities. Each parent completed the questionnaire of knowledge and beliefs about ADHD (CASE ADHD, parent's version). The questionnaire was created for this study as an instrument with three versions: a) Parents, b) Teachers, c) Health professionals. Results of parent's version were included in this report. This questionnaire incorporates information of other instruments such as Barkley's Evaluation Questionnaire and the one used in the National Colombian Survey for the Consensus of treatment of ADHD 2008. CASE ADHD includes three parts: 1. An identification record with the mother's or father's general data, 2. The ADHD Rating Scale-IV, and 3. A 36 multiple choice questionnaire related to six main areas: a) The caretaker report of symptoms and clinical characteristics related with ADHD, b) The knowledge about ADHD, c) The pathways to care report, d) The Beliefs about ADHD treatment, e) The professional mental health's performance, and f) The parent's perceptions about ADHD. The questionnaire must be completed with the assistance of a mental health professional. The average application time is 30 minutes. For statistical analysis central tendency measures were used; as means, standard deviations and percentages. Results The total sample was integrated by 288 parents of children or adolescents. The 80.1% of the questionnaires were fulfilled by the mother. The mean age of those who answered was 40.06 years, 25.4% reported to complete professional studies. The mean age of patients was 11.15 years (SD = 3.54), 58% were children and 74% were male, their ADHDRS-IV average score was 27.5 (SD = 14.03). Knowledge about ADHD. The 85.4% (N = 246) of the surveyed sample considered ADHD as a disease and 8.3% as a rearing difficulty. The 69.2% (N = 198) of parents said they knew what is ADHD, but only 62.1% reported to receive information by the physician or psychologist about this condition. Attitudes about ADHD. When questioned about what would they do if they suspected that their child had ADHD, 35.1 % (N = 101) would consult a psychiatrist, 21.2% a psychologist, and 12.2% a neurologist or pediatric neurologist. The 28% of parents were deemed unable to manage their child's behavior problem. When we asked about who is able to diagnose ADHD, 49.5% answered that the psychologist, 48.5% the psychiatrist and 19.8% that the pediatrician. The psychiatrist was considered able to treat this condition by 45.8% of the sample followed by psychologist (19.8%), and neurologist (10.4%). Beliefs about diagnosis and treatment. Nearly 63% of the sample (N = 183) considered that the best treatment for ADHD was the combined treatment; 16.3% preferred the psychological approach and psychopharmacology was chosen by only 6.6%. Almost half (48.5%, N= 129) of the sample considered that drug treatment only supports the psychosocial treatment and does not have a therapeutic effect by itself, 46.2% (N = 133) of the sample believed that <

Introducción A pesar de la evidencia científica acerca de las características neurobiológicas del Trastorno por Déficit de Atención e Hiperactividad (TDAH) que apoya el uso de medicamentos para su tratamiento, este padecimiento sigue generando controversia con respecto a su existencia, su persistencia a lo largo de la vida y su tratamiento óptimo. La prevalencia del TDAH a nivel mundial es alta. Los estudios epidemiológicos muestran que 3 a 5% de los niños en edad escolar pueden recibir este diagnóstico. En México se estima que hay aproximadamente 33 millones de niños y adolescentes, de los cuales 1.5 millones podrían ser diagnosticados con TDAH. En el contexto clínico, al menos 30% de los pacientes que acuden a valoración de primera vez en los servicios de psiquiatría infantil presentan problemas de inatención, hiperactividad o impulsividad. Algunos estudios epidemiológicos han mostrado que sólo el 25% de los padres de sujetos con síntomas de trastornos de conducta o del afecto consideraban que sus hijos necesitaban atención médica, y de ellos, el 13% acudió a los servicios de salud mental. La búsqueda de atención especializada se ha asociado con una mayor intensidad del trastorno y un mayor nivel educativo de los padres. Diversas publicaciones relacionadas con el tratamiento del TDAH a lo largo de la vida resaltan la importancia de la intervención multimodal, es decir, un tratamiento multidisciplinario que va más acorde al modelo biopsicosocial el cual, a su vez, se encuentra relacionado con los factores etiológicos y de pronóstico a mediano y largo plazo en el TDAH. En diversos estudios se ha subrayado la importancia de brindar educación adecuada sobre el trastorno y su tratamiento. También sugieren que un mejor entendimiento acerca de las creencias y conocimientos de los padres de niños y adolescentes con TDAH ayudará a mejorar los mecanismos de comunicación, atención y colaboración entre los distintos elementos participantes en el tratamiento del TDAH y reducirá el tiempo entre la identificación del problema y el inicio del tratamiento. Objetivo Describir los conocimientos, las creencias y actitudes de los padres de niños y adolescentes con TDAH acerca de la naturaleza de la enfermedad, la conducta en la búsqueda de atención médica y su tratamiento. Material y métodos La muestra fue conformada por padres de niños y adolescentes que habían recibido el diagnóstico de TDAH por un clínico calificado. Participaron cuatro centros de atención psiquiátrica, tres en la Ciudad de México y otro en la ciudad de San Luis Potosí. El instrumento principal (CASO ADH padres) es un cuestionario autoaplicable y fue escrito específicamente para este estudio. CASO ADHD es un instrumento con tres versiones: a) Padres, b) Maestros y c) Profesionales de la salud. En este estudio se exponen los resultados de la primera versión. Resultados La muestra total se conformó de 288 padres. El 69.2% dijo saber qué es el TDAH, 85.4% consideró al TDAH como una enfermedad y el 8.3% como una dificultad de la crianza; el resto lo consideró un mito, una moda, un invento de la industria farmacéutica o no existente. Alrededor del 63% de la muestra consideró que el mejor tratamiento para el TDAH sería el tratamiento combinado, el 16.3% prefirió el enfoque psicológico y sólo 6.6% eligió la psicofarmacología. Casi la mitad de la muestra, 48.5%, consideró que el tratamiento farmacológico solamente apoya al tratamiento psicosocial. La mayoría de los padres (60%) identificaron los síntomas de sus hijos en su propia conducta durante los años escolares. Conclusiones Es importante mejorar la cantidad y la calidad de educación acerca del TDAH y su tratamiento entre los padres de los pacientes, para que sus decisiones terapéuticas sean más informadas y tengan mejor efecto sobre el pronóstico del paciente.

Strength of the Zn-N coordination bond in zinc porphyrins on the basis of experimental thermochemistry.

The compound, 5,10,15,20-tetrakis(4-methoxyphenyl)porphine zinc(II) (ZnTMPP), was prepared, and its thermochemical properties were experimentally established. The standard molar energy of combustion (Delta(c)U degrees m) was determined from oxygen rotating-bomb combustion calorimetry experiments. The standard molar enthalpies of combustion (Delta(c)H degrees m) and formation (Delta(f)H degrees m) were derived. The enthalpy of sublimation (Delta(cr)(g)H degrees m) was determined by Knudsen effusion at high temperatures. With these results, the standard molar enthalpies of formation and atomization (Delta(at)H degrees m) in the gas state were calculated. A summary of the results at T = 298.15 K (p degrees = 0.1 MPa) is shown in Table 1. Using these results and those previously obtained for the free ligand, 5,10,15,20-tetrakis(4-methoxyphenyl)porphine, the mean dissociation enthalpy for the Zn-N coordination bond is obtained as D(Zn-N) = (160 +/- 9) kJ.mol-1. This value is consistent with the results obtained using the same experimental approach in a similar system (5,10,15,20-tetraphenylporphine, TPP/ZnTPP) reported elsewhere. A discussion of the strength for the Zn-N coordination bond is made in terms of the structural and electronic features of the molecules involved.

A study of the growth for the microalga Chlorella vulgaris by photo-bio-calorimetry and other on-line and off-line techniques.

Calorimetry and other on-line techniques are used for the first time as complement to the traditional off-line methods in order to follow the growth of the green Chlorella vulgaris microalgae. A 2-L photo-bio-reactor was adapted from a commercial calorimeter used previously to study heterotrophic microbial growth. An external source of light was added to favor the photosynthesis of the autotrophic cells. Heterotrophic growth was also tested with external glucose in the broth. A third mode, mixotrophic, allowed faster autotrophic plus heterotrophic growth. Calorimetric measurements were performed considering the corresponding calibrations in order to consider only the energy involved during the microalgal growth. The three different modes of Chlorella cultures were energetically characterized. Besides calorimetry, the weight of diluted nitric acid added to maintain the pH of the culture was correlated with the cellular growth and the nitrogen composition of the algae. Additionally, the on-line infrared spectroscopy proved to be an efficient technique to follow the composition of the broth in glucose, nitrates, and phosphates. These results were compared and complemented with some classic off-line techniques used to track this kind of cultures.

Thermodynamics of microbial growth and metabolism: an analysis of the current situation.

This paper attempts to review in how far thermodynamic analysis can be used to understand and predict the performance of microorganisms with respect to growth and bio-product synthesis. In the first part, a simple thermodynamic model of microbial growth is developed which explains the relationship between the driving force for growth in terms of Gibbs energy dissipation and biomass yield. From the currently available literature, it appears that the Gibbs energy dissipation per C-mol of biomass grown, which represents the driving force for chemotrophic growth, may have been adapted by evolutionary processes to strike a reasonable compromise between metabolic rate and growth efficiency. Based on empirical correlations of the C-molar Gibbs energy dissipation, the wide variety of biomass yields observed in nature can be explained and roughly predicted. This type of analysis may be highly useful in environmental applications, where such wide variations occur. It is however not able to predict biomass yields in very complex systems such as mammalian cells nor is it able to predict or to assess bio-product or recombinant protein yields. For this purpose, a much more sophisticated treatment that accounts for individual metabolic pathways separately is required. Based on glycolysis as a test example, it is shown in the last part that simple thermodynamic analysis leads to erroneous conclusions even in well-known, simple cases. Potential sources for errors have been analyzed and can be used to identify the most important needs for future research.