Aislamiento de cepas de traustoquitridios en la zona costera de Puerto Montt, Chile y evaluación de la producción de ácido docosahexaenoico (C22:6n-3, DHA)

Cuarenta y seis cepas que presentaron las característicasmorfológicas descritas para traustoquitridios fueron aisladasdesde muestras colectadas en cinco localidades de la zona costera de Puerto Montt, Chile, utilizando la técnica de polen de pino. Las 16 cepas que mostraron el perfil característico de tres bandas cuando el ADN fue amplificado con un conjunto de tres cebadores (FA1RA1, FA2RA2 y FA3RA3) diseñados para estos microorganismos(17), fueron cultivadas en medio líquido para evaluar la producción de ácido docosahexaenoico (C22:6n-3, DHA). El cultivo se realizó en matraces de Erlenmeyer agitados y la composición del medio basal fue: glucosa 10 g/L, extracto de levadura 4 g/L, en agua de mar diluida al 70%. Sólo 6 cepasprodujeron lípidos en los que se detectó DHA; los mayorescontenidos de DHA en los ácidos grasos totales y de DHA en la biomasa fueron 46,4% (cepa G4) y 36,2 mg/g (cepa M12-X1), respectivamente. El análisis de filogenia molecular basado en el alineamiento de la secuencia del gen que codifica para el ARN de la subunidad pequeña ribosomal (18S rRNA) confirmó que las tres cepas nativas que producen DHA pertenecen al phylum Labyrinthulomycota. Pruebas preliminares demostraron que es posible incrementar la concentración de biomasa (83%), el contenido de DHA en la biomasa (153%) y la concentración de DHA (71%) a través de la inclusión de glutamato monosódico en el medio de cultivo basal.

Lithium Tetraborate as a Neutron Scintillation Detector: A Review

The electronic structure and translucent nature of lithium tetraborate (Li2B4O7) render it promising as a scintillator medium for neutron detection applications. The inherently large neutron capture cross-section due to 10B and 6Li isotopes and the ease with which Li2B4O7 can be enriched with these isotopes, combined with the facile inclusion of rare earth dopants (occupying the Li+ sites), are expected to improve the luminescent properties, as well as the neutron detection efficiency, of Li2B4O7. The electronic structure of both doped and undoped Li2B4O7 were explored, using photoemission and inverse photoemission spectroscopies, optical measurements, and theoretical computational studies such as density functional theory. The scintillation properties are further enhanced because of the wide bandgap, makingLi2B4O7 extremely translucent, so that capturing the neutron scintillation output is neither hindered nor diminished. Therefore, in this review, demonstrations of the possible amplification of neutron capture efficiencies, courtesy of rare-earth dopants, along with insights into a significantly large charge production (associated with neutron capture), are presented

Measurements of the mass and width of the eta_c using psi' -> gamma eta_c

The mass and width of the lowest lying S-wave spin singlet charmonium state, the eta_c, are measured using a data sample of 1.06x10^8 psi' decays collected with the BESIII detector at the BEPCII storage ring. We use a model that incorporates interference between the signal reaction, psi' -> gamma eta_c, and a non-resonant radiative background to successfully describe the line shape of the eta_c. We measure the eta_c mass to be 2984.3 +- 0.6 +- 0.6 MeV/c^2 and the total width to be 32.0 +- 1.2 +- 1.0 MeV, where the first errors are statistical and the second are systematic.Comment: 7 pages, 1 figure, 1 table, matches Phys. Rev. Lett. versio

Hybrid neural network model for simulating sorbitol synthesis by glucose-fructose oxidoreductase in Zymomonas mobilis CP4

A hybrid neural network model for simulating the process of enzymatic reduction of fructose to sorbitol process catalyzed by glucose-fructose oxidoreductase in Zymomonas mobilis CP4 is presented. Data used to derive and validate the model was obtained from experiments carried out under different conditions of pH, temperature and concentrations of both substrates (glucose and fructose) involved in the reaction. Sonicated and lyophilized cells were used as source of the enzyme. The optimal pH for sorbitol synthesis at 30º C is 6.5. For a value of pH of 6, the optimal temperature is 35º C. The neural network in the model computes the value of the kinetic relationship. The hybrid neural network model is able to simulate changes in the substrates and product concentrations during sorbitol synthesis under pH and temperature conditions ranging between 5 and 7.5 and 25 and 40º C, respectively. Under these conditions the rate of sorbitol synthesis shows important differences. Values computed using the hybrid neural network model have an average error of 1.7·10-3 mole

Biotechnological alternatives for omega-3 polyunsaturated fatty acids production Alternativas biotecnológicas para la producción de ácidos grasos poliinsaturados omega-3

Fish oils are the main sources of omega-3 (ω3) polyunsaturated acids (PUFA) such as eicosapentaenoic (C20:5ω3) and docosahexaenoic (C22:6ω3) acids. World demand for ω3 PUFA shows an increasing trend mainly due to the growth of the aquaculture industry and also due to the increasing demand for specific PUFA used as food supplements. Bacteria, fungi, microalgae and thraustochytrids are biotechnotogical PUFA alternatives to fish oils. These sources are characterized by specific PUFA profiles whose productivity depends on strain and growth conditions. PUFA content in bacteria is low; microalgae synthesize mixtures of PUFA; fungi system productivity is low due to long fermentation times. In heterotrofic cultures of thraustochytrids high concentrations of PUFA can be obtained. Moreover, many strains are able to synthesize a single ω3 PUFA. The optimization of fermentation systems and the development of technology capable of large-scale production are needed in order to make these alternativ