RESUMO

The progressive influx of engineered nanoparticles (ENPs) into the soil matrix catalyses a fundamental transformation in the equilibrium dynamics between the soil and the edaphic solution. This all-encompassing investigation is geared towards unravelling the implications of an array of ENP types, diverse dosages and varying incubation durations on the kinetics governing Cd2+ sorption within Ultisol soils. These soils have been subjected to detailed characterizations probing their textural and physicochemical attributes in conjunction with an exhaustive exploration of ENP composition, structure and morphology. To decipher the intricate nuances of kinetics, discrete segments of Ultisol soils were subjected to isolated systems involving ENP dosages of 20 and 500 mg ENPs·kg-1 (AgNPs, CuNPs and FeNPs) across intervals of 1, 3 and 6 months. The comprehensive kinetic parameters were unveiled by applying the pseudo-first-order and pseudo-second-order models. At the same time, the underlying sorption mechanisms were studied via the intra-particle diffusion model. This study underscores the substantial impact of this substrate on the kinetic behaviours of contaminants such as Cd, emphasizing the need for its consideration in soil-linked economic activities and regulatory frameworks to optimize resource management.

RESUMO

Gynerium sagittatum es una gramínea ampliamente utilizada en la costa Caribe colombiana como fuente de fibra natural para la elaboración de artesanías, particularmente por la comunidad Zenú. En la presente investigación se evaluó el efecto de diferentes concentraciones de enzimas: celulasa y macerozima a diferentes tiempos de incubación y sus interacciones en el aislamiento de protoplastos. Los protoplastos se obtuvieron del mesófilo foliar de vitroplantas de G. sagittatum expuesto a combinaciones enzimáticas de celulasa (1.5 y 2.0%), con macerozima (0.3, 0.6 y 0.9%), durante 3, 6 y 9 horas de incubación, para un total de 18 tratamientos con 5 réplicas cada uno. Los mayores números de protoplastos aislados correspondieron a T18 (2.0% celulasa, 0.9% macerozima), T12 (2.0% de celulasa, 0.3% macerozima), T3 (1.5% de celulasa, 0.3% de macerozima) y T6 (1.5% de celulasa, 0.6% de macerozima) por 9 horas de incubación cada uno, con valores de 88.625, 83.000, 75.000 y 53.375 protoplastos/mL respectivamente. El tiempo de incubación fue significativo en el aislamiento de los protoplastos (p<0.05). Las predicciones entre factores mostraron que una interacción de 2.0% de celulasa y 0.9% de macerozima permite obtener 44.302 protoplastos/mL, mientras que las interaciciones tiempo de incubación-celulasa y tiempo de incubación-macerozima mostraron que es posible obtener 72.073 y 71.212 protoplastos/mL con 2.0% de celulasa y 0.9% macerozima por 9 horas de incubación cada una respectivamente. Los resultados indican que la aplicación de estas enzimas permite obtener cantidades considerables de protoplastos de G. sagittatum a partir de explantes cultivados in vitro.

Gynerium sagittatum is a graminaceous plant widely used in the Caribbean coast of Colombia as a natural fiber source for the elaboration of handicrafts, particularly by the Zenú community. In the present investigation, the effect of different concentrations of cellulase and macerozyme enzymes at different incubation times and their interaction in the isolation of protoplasts was evaluated. Protoplasts were obtained from leaf mesophyll of G. sagittatum vitroplants exposed to enzymatic combinations of cellulase (1.5 and 2.0%), with macerozyme (0.3, 0.6 and 0.9%), for 3, 6 and 9 hours of incubation, for a total of 18 treatments with 5 replicates each. The highest numbers of isolated protoplasts corresponded to T18 (2.0% cellulase, 0.9% macerozyme), T12 (2.0% cellulase, 0.3% macerozyme), T3 (1.5% cellulase, 0.3% macerozyme) and T6 (1.5% cellulase, 0.6% macerozyme); at 9 hours incubation. The protoplast number for these treatments were: 88.625, 83.000, 75.000 and 53.375 protoplasts/mL respectively. Incubation time was significant in the isolation of protoplasts (p<0.05). The predictions between the factors showed that with an interaction of 2.0% cellulase and 0.9% macerozyme it is possible to obtain 44.302 protoplasts/mL, likewise, the incubation time-cellulase and incubation time-macerozyme interactions showed that it is possible to obtain 72.073 and 71.212 protoplasts/mL with 2.0% cellulase and 0.9% macerozyme for 9 hours of incubation respectively. The results indicate that the use of these enzymes and time, allows the isolation of of protoplasts from G. sagittatum in vitro plants.

RESUMO

Considering there are several difficulties and limitations in labeling stem cells using multifunctional nanoparticles (MFNP), the purpose of this study was to determine the optimal conditions for labeling human bone marrow mesenchymal stem cells (hBM-MSC), aiming to monitor these cells in vivo. Thus, this study provides information on hBM-MSC direct labeling using multimodal nanoparticles in terms of concentration, magnetic field, and period of incubation while maintaining these cells' viability and the homing ability for in vivo experiments. The cell labeling process was assessed using 10, 30, and 50 µg Fe/mL of MFNP, with periods of incubation ranging from 4 to 24 h, with or without a magnetic field, using optical microscopy, near-infrared fluorescence (NIRF), and inductively coupled plasma mass spectrometry (ICP-MS). After the determination of optimal labeling conditions, these cells were applied in vivo 24 h after stroke induction, intending to evaluate cell homing and improve NIRF signal detection. In the presence of a magnetic field and utilizing the maximal concentration of MFNP during cell labeling, the iron load assessed by NIRF and ICP-MS was four times higher than what was achieved before. In addition, considering cell viability higher than 98%, the recommended incubation time was 9 h, which corresponded to a 25.4 pg Fe/cell iron load (86% of the iron load internalized in 24 h). The optimization of cellular labeling for application in the in vivo study promoted an increase in the NIRF signal by 215% at 1 h and 201% at 7 h due to the use of a magnetized field during the cellular labeling process. In the case of BLI, the signal does not depend on cell labeling showing no significant differences between unlabeled or labeled cells (with or without a magnetic field). Therefore, the in vitro cellular optimized labeling process using magnetic fields resulted in a shorter period of incubation with efficient iron load internalization using higher MFNP concentration (50 µgFe/mL), leading to significant improvement in cell detection by NIRF technique without compromising cellular viability in the stroke model.

RESUMO

The flameback pygmy angelfish Centropyge aurantonotus, highly appreciated and valued by the aquarium market, is heavily harvested and traded. Temperature is one of the abiotic factors that has the most influence on fish development, especially in the early stages of life. For captive production, it is essential to know the appropriate environmental parameters for each species. In this sense, this study aimed to evaluate the influence of temperature on the embryonic development and hatching rates of C. aurantonotus incubated at six different temperatures (20, 22, 24, 26, 28, 30°C). Embryonic development events were very similar in terms of morphological and chronological characteristics compared with other species of the genus Centropyge. Incubation time was inversely proportional to temperature. The treatment at 22°C required twice the time of that required by 30°C treatment for hatching to occur. The best incubation temperature range was 24-28°C. Values below 22°C and at 30°C showed lower hatching rates compared with other treatments. Based on these results, the recommended temperature at which to incubate C. aurantonotus eggs is between 24-28°C.

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BACKGROUND: Laser-assisted MAL-PDT has been reported to increase the effectiveness of conventional PDT. Nonetheless, clinical effects of this association when reducing MAL incubation time is poorly discussed. Furthermore, the association of acoustic pressure wave ultrasound with laser-assisted MAL-PDT with short incubation time for field cancerization had not been reported before. OBJECTIVES: To compare clinical effects of ablative fractional laser-assisted MAL-PDT associated with acoustic pressure wave ultrasound (IMPACT US) with 1-hour incubation time and conventional MAL-PDT for skin field cancerization on the forearms, as well as the impact on safety and tolerability. METHODS: Fifteen patients with 638 AK (grade I-III) with field cancerized-skin on the forearms were enrolled in this left-right trial. Two protocols were randomly chosen. One side was treated with conventional MAL-PDT, whereas the other with laser-assisted MAL-PDT associated with acoustic pressure wave ultrasound with 1-hour incubation time. Actinic keratoses were quantitively measured, and the other signs of sun-damaged skin, like pigmentation and texture, in field cancerized skin were qualitatively evaluated before and after six months. Side effects were assessed subjectively during the procedure and one week after. RESULTS: All patients completed the study. At six months after treatment, both protocols reduced the number of AK (72%; CO2 + PDT, and 65%; MAL-PDT). The difference between these two protocols was not statistically significant (p = 0.77). The improvement of pigmentation and texture of field cancerized skin was more significant on the side treated with laser-assisted MAL-PDT associated with acoustic pressure wave ultrasound. Both protocols were well tolerated and without significant difference in adverse events. CONCLUSION: Laser-assisted MAL-PDT using CO2 laser and acoustic pressure wave ultrasound with short incubation time of 1 h was as effective as conventional MAL-PDT for field-cancerized skin with actinic keratosis in forearms with better cosmetic outcome.

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Sorghum, which is consumed in Tunisia as human food, suffers from severe colonization by several toxigenic fungi and contamination by mycotoxins. The Tunisian climate is characterized by high temperature and humidity that stimulates mold proliferation and mycotoxin accumulation in foodstuffs. This study investigated the effects of temperature (15, 25 and 37 °C), water activity (a w, between 0.85 and 0.99) and incubation time (7, 14, 21 and 28 d) on fungal growth and aflatoxin B1 (AFB1) production by three Aspergillus flavus isolates (8, 10 and 14) inoculated on sorghum grains. The Baranyi model was applied to identify the limits of growth and mycotoxin production. Maximum diameter growth rates were observed at 0.99 a w at 37 °C for two of the isolates. The minimum a w needed for mycelial growth was 0.91 at 25 and 37 °C. At 15 °C, only isolate 8 grew at 0.99 a w. Aflatoxin B1 accumulation could be avoided by storing sorghum at low water activity levels (≤0.91 a w). Aflatoxin production was not observed at 15 °C. This is the first work on the effects of water activity and temperature on A. flavus growth and AFB1 production by A. flavus isolates on sorghum grains.

El sorgo, que se consume en Túnez como alimento humano, puede sufrir la colonización severa de varios hongos toxicogénicos, con la consiguiente bioacumulación de micotoxinas. Además, el clima de Túnez, caracterizado por las altas temperaturas y humedad, estimula el crecimiento fúngico y la acumulación de micotoxinas en los productos alimenticios. Este estudio investigó los efectos de la temperatura (15, 25 y 37 °C), la actividad de agua (a w) (entre 0,85 y 0,99) y el tiempo de incubación (7, 14, 21 y 28 días) sobre el crecimiento y la producción de aflatoxina B1 (AFB1) de 3 aislados de Aspergillus flavus (designados como 8, 10 y 14) que se inocularon sobre granos de sorgo. El modelo Baranyi se aplicó para identificar los límites del crecimiento y la producción de micotoxinas. Las tasas máximas de crecimiento para 2 de los aislados se observaron en la combinación 0,99 a w y 37 °C. La a w mínima necesaria para el crecimiento del micelio fue de 0,91 a 25 °C y 37 °C. A 15 °C, solo el aislado 8 creció a 0,99 a w, pero fue incapaz de producir la aflatoxina B1. Es posible evitar la acumulación de aflatoxina B1 en el sorgo almacenándolo a baja actividad de agua (≤ 0,91 a w). Este es el primer trabajo que ha estudiado el efecto de la actividad del agua y la temperatura sobre el crecimiento de aislados de A. flavus y su producción de aflatoxina B1 en granos de sorgo.

Assuntos

RESUMO

Sorghum, which is consumed in Tunisia as human food, suffers from severe colonization by several toxigenic fungi and contamination by mycotoxins. The Tunisian climate is characterized by high temperature and humidity that stimulates mold proliferation and mycotoxin accumulation in foodstuffs. This study investigated the effects of temperature (15, 25 and 37°C), water activity (aw, between 0.85 and 0.99) and incubation time (7, 14, 21 and 28 d) on fungal growth and aflatoxin B1 (AFB1) production by three Aspergillus flavus isolates (8, 10 and 14) inoculated on sorghum grains. The Baranyi model was applied to identify the limits of growth and mycotoxin production. Maximum diameter growth rates were observed at 0.99 a(w) at 37°C for two of the isolates. The minimum aw needed for mycelial growth was 0.91 at 25 and 37°C. At 15°C, only isolate 8 grew at 0.99 a(w). Aflatoxin B1 accumulation could be avoided by storing sorghum at low water activity levels (≤0.91 a(w)). Aflatoxin production was not observed at 15°C. This is the first work on the effects of water activity and temperature on A. flavus growth and AFB1 production by A. flavus isolates on sorghum grains.

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RESUMO

Os macroinvertebrados bentônicos são amplamente utilizados como bioindicadores de qualidade da água em todo o mundo, devido, as suas características fisiológicas e morfológicas. O objetivo do estudo foi avaliar a qualidade da água do rio das Pedras,no município de Matelândia, Oeste do Estado do Paraná, na estação seca, utilizando-se de macroinvertebrados bentônicos como bioindicador, e identificar o tempo ideal de incubação dos litter bags. Sessenta litter bags foram confeccionados com folhas de árvores nativas provenientes da floresta ripária e incubadosno rio das Pedras. Oito litter bags foram coletados nos intervalos de três, sete,14, 28, 35 e 42 dias. Os macroinvertebrados bentônicos foram identificados em nível de família e foi aplicado o índice Biological Monitoring Working Party Score System. Com este estudo concluiu-se que o rio das Pedras possui águas não poluídas, demonstrando que o sistema é perceptivelmente não alterado. O tempo de incubação dos litter bags para obtenção do resultado quanto à avaliação da qualidade de água pelo índice Biological Monitoring Working Party Score System foi de sete dias e para analisar a estrutura da comunidade de macroinvertebrados bentônicos foi de 28 dias.

Benthic macroinvertebrates are widely used as bioindicators of water quality due to their physiological and morphological characteristics. The aim of this study was to evaluate the water quality at Rio das Pedras, in the city of Matelândia, Western Paraná, in the dry season, using benthic macroinvertebrates as bioindicators, and to identify the optimal time for the incubation of litter bags. Sixty litter bags were prepared with leaves from native trees from the riparian forest and incubated in Rio das Pedras river. Eight litter bags were collected at intervals of 3, 7, 14, 28, 35 and 42 days. The benthic macroinvertebrates were identified at the family level and the Biological Monitoring Working Party Score System index was applied. With this study, it can be concluded that the Rio das Pedras river has unpolluted waters, demonstrating that the system has hardly been changed. The litter bag incubation period in order to obtain the results for evaluating the water quality index for the Biological Monitoring Working Party Score System was of seven days, and the period to analyze the structure of the benthic macroinvertebrate community was of 28 days.

Los macroinvertebrados bentónicos son ampliamente utilizados como bioindicadores de calidad del agua en todo el mundo, debido sus características fisiológicas y morfológicas. El objetivo de este estudio ha sido evaluar la calidad de las aguas del Rio das Pedras, en el municipio de Matelândia, oeste del Estado de Paraná, en la estación seca, utilizándose de macroinvertebrados bentónicos como bioindicador, e identificar el tiempo ideal de incubación de los litter bags. Sesenta litter bags han sido confeccionados con hojas de árboles nativas procedentes de la floresta ribera e incubados en el Rio das Pedras. Ocho litter bags fueron recogidos en intervalos de tres, siete, catorce, veintiocho, treinta y cinco y cuarenta y dos días. Los macroinvertebrados bentónicos fueron identificados en nivel de familia y aplicado el índice Biological Monitoring Working Party Score System. Con esta investigación se ha concluido que el Rio das Pedras no tiene aguas contaminadas, demostrando que el sistema no es alterado. El tiempo de incubación de los litter bags para obtención del resultado cuanto a la evaluación de la calidad del agua por el índice Biological Monitoring Working Party Score System fue de siete días, y para analizar la estructura de la comunidad de macroinvertebrados bentónicos fue de 28 días.

Assuntos

RESUMO

We hypothesize that the Ferric Reducing Antioxidant Power (FRAP) assay that follows the reaction of Fe3+-TPTZ at 593 nm underestimates the antioxidant capacity of fruits, since the standardized time of the reaction (4 min) is not enough to titrate all the reducing compounds available. We measured FRAP, total phenolics and anthocyanins content in a variety of Chilean berry fruits (blueberries, blackberries, raspberries and strawberries) and apples (cv. Fuji, Granny Smith, Pink Lady, Red Delicious and Royal Gala). Taking into account the dependence of FRAP on the time course of the reaction, we propose to measure FRAP indexes after 1 min (FRAP-1), 30 min (FRAP-30) and 120 min (FRAP-120) of incubation. Most fruit extracts showed significant correlations between the antioxidant capacity and the incubation time, although in some cases the FRAP indexes did not correlate with the total phenolics and/or anthocyanins content. In fact, in apples and berries the correlation between anthocyanins content and FRAP indexes decreased with the incubation time. It is concluded that the fruit extracts analyzed require an incubation period higher than the established in the original experimental protocol to reach the equilibrium, due to the presence of a complex mixture of antioxidant compounds. In addition, a kinetic profile should be realized in each sample studied to establish the most suitable incubation period to titrate all the reactive antioxidant species.

Se plantea que el ensayo de la capacidad antioxidante de frutas, medido según el poder reductor de hierro (FRAP), que sigue la reacción de Fe3+-TPTZ a 593 nm, subestima la capacidad antioxidante, debido a que el tiempo de reacción (4 min) no sería suficiente para que reaccionen todos los compuestos reductores disponibles en las muestras. Se analizó la capacidad antioxidante FRAP, el contenido de fenoles y de antocianinas en diversos berries (arándano, mora, frambuesa y frutilla) y manzanas (cv. Fuji, Granny Smith, Pink Lady, Red Delicious y Royal Gala). Tomando en cuenta la dependencia del tiempo de incubación en el valor FRAP, se propone medir los índices FRAP después de 1 min (FRAP-1), 30 min (FRAP-30) y 120 min (FRAP-120). Diversos extractos de las frutas analizadas mostraron una correlación significativa entre la capacidad antioxidante y el tiempo de incubación; sin embargo, en algunos casos los índices FRAP no se correlacionaron con el contenido de fenoles totales y/o antocianinas. En efecto, en manzanas y berries la correlación entre el contenido de antocianinas e índices FRAP disminuyó con el tiempo de incubación. Se concluye que los extractos analizados requieren un tiempo de incubación mayor al que establece el protocolo analítico original para alcanzar el equilibrio, debido a la presencia de una compleja mezcla de compuestos antioxidantes. Además, el perfil cinético de cada muestra debería ser estudiado para establecer el periodo de incubación más adecuado para titular todas las especies antioxidantes reactivas.

Assuntos

RESUMO

Estudos indicam que um dos problemas mais sérios que afetam os manejos pré e pós-colheita do arroz é a presença de fungos das espécies Aspergillus ou Penicillium, potencialmente produtores de micotoxinas. Os objetivos deste trabalho foram avaliar a capacidade produtora de aflatoxina B1 de cepas isoladas do arroz e observar o efeito do pré-inóculo nas mesmas. Foram utilizados três isolados de Aspergillus flavus, conhecidamente já produtores, que foram testados nas temperaturas de 20 e 25°C, combinadas com tempos de incubação 11, 14 e 21 dias. Os pré-inóculos utilizados foram Yeast Extrat Sucrose (YES) e Czapeck Yeast Extrat (CYA). Todas as cepas retiradas do pré-inóculo em meio YES e inoculadas no arroz, em temperatura de 25°C/18 dias e 20°C/14 dias, produziram aflatoxina B1. O meio CYA apresentou menor desempenho, uma vez que as três cepas testadas não produziram aflatoxina B1 na combinação 20°C/14 dias. A 25°C/11 dias de incubação a aflatoxina B1 não foi detectada.

The production of aflatoxin in rice by three isolates of Aspergillus flavus was investigated for different culture conditions (temperature and incubation time) and previous inoculum (YES- Yeast Extrat Sucrose and CYA- Czapeck Yeast Extrat). All strains withdrawn from the previous inoculum medium YES and inoculated in the rice in temperature of 25°C/18 days and 20°C/14 days, produced aflatoxin B1. The medium CYA had lower performance since the three strains tested did not produce aflatoxin B1 in the combination 20°C/14 days. At 25°C/11 days of incubation time aflatoxin was not detectable.

RESUMO

The production of aflatoxin in rice by three isolates of Aspergillus flavus was investigated for different culture conditions (temperature and incubation time) and previous inoculum (YES- Yeast Extrat Sucrose and CYA- Czapeck Yeast Extrat). All strains withdrawn from the previous inoculum medium YES and inoculated in the rice in temperature of 25°C/18 days and 20°C/14 days, produced aflatoxin B1. The medium CYA had lower performance since the three strains tested did not produce aflatoxin B1 in the combination 20°C/14 days. At 25°C/11 days of incubation time aflatoxin was not detectable.

Estudos indicam que um dos problemas mais sérios que afetam os manejos pré e pós-colheita do arroz é a presença de fungos das espécies Aspergillus ou Penicillium, potencialmente produtores de micotoxinas. Os objetivos deste trabalho foram avaliar a capacidade produtora de aflatoxina B1 de cepas isoladas do arroz e observar o efeito do pré-inóculo nas mesmas. Foram utilizados três isolados de Aspergillus flavus, conhecidamente já produtores, que foram testados nas temperaturas de 20 e 25°C, combinadas com tempos de incubação 11, 14 e 21 dias. Os pré-inóculos utilizados foram Yeast Extrat Sucrose (YES) e Czapeck Yeast Extrat (CYA). Todas as cepas retiradas do pré-inóculo em meio YES e inoculadas no arroz, em temperatura de 25°C/18 dias e 20°C/14 dias, produziram aflatoxina B1. O meio CYA apresentou menor desempenho, uma vez que as três cepas testadas não produziram aflatoxina B1 na combinação 20°C/14 dias. A 25°C/11 dias de incubação a aflatoxina B1 não foi detectada.

RESUMO

The production of aflatoxin in rice by three isolates of Aspergillus flavus was investigated for different culture conditions (temperature and incubation time) and previous inoculum (YES- Yeast Extrat Sucrose and CYA- Czapeck Yeast Extrat). All strains withdrawn from the previous inoculum medium YES and inoculated in the rice in temperature of 25°C/18 days and 20°C/14 days, produced aflatoxin B1. The medium CYA had lower performance since the three strains tested did not produce aflatoxin B1 in the combination 20°C/14 days. At 25°C/11 days of incubation time aflatoxin was not detectable.

Estudos indicam que um dos problemas mais sérios que afetam os manejos pré e pós-colheita do arroz é a presença de fungos das espécies Aspergillus ou Penicillium, potencialmente produtores de micotoxinas. Os objetivos deste trabalho foram avaliar a capacidade produtora de aflatoxina B1 de cepas isoladas do arroz e observar o efeito do pré-inóculo nas mesmas. Foram utilizados três isolados de Aspergillus flavus, conhecidamente já produtores, que foram testados nas temperaturas de 20 e 25°C, combinadas com tempos de incubação 11, 14 e 21 dias. Os pré-inóculos utilizados foram Yeast Extrat Sucrose (YES) e Czapeck Yeast Extrat (CYA). Todas as cepas retiradas do pré-inóculo em meio YES e inoculadas no arroz, em temperatura de 25°C/18 dias e 20°C/14 dias, produziram aflatoxina B1. O meio CYA apresentou menor desempenho, uma vez que as três cepas testadas não produziram aflatoxina B1 na combinação 20°C/14 dias. A 25°C/11 dias de incubação a aflatoxina B1 não foi detectada.

RESUMO

The production of aflatoxin in rice by three isolates of Aspergillus flavus was investigated for different culture conditions (temperature and incubation time) and previous inoculum (YES- Yeast Extrat Sucrose and CYA- Czapeck Yeast Extrat). All strains withdrawn from the previous inoculum medium YES and inoculated in the rice in temperature of 25°C/18 days and 20°C/14 days, produced aflatoxin B1. The medium CYA had lower performance since the three strains tested did not produce aflatoxin B1 in the combination 20°C/14 days. At 25°C/11 days of incubation time aflatoxin was not detectable.

Estudos indicam que um dos problemas mais sérios que afetam os manejos pré e pós-colheita do arroz é a presença de fungos das espécies Aspergillus ou Penicillium, potencialmente produtores de micotoxinas. Os objetivos deste trabalho foram avaliar a capacidade produtora de aflatoxina B1 de cepas isoladas do arroz e observar o efeito do pré-inóculo nas mesmas. Foram utilizados três isolados de Aspergillus flavus, conhecidamente já produtores, que foram testados nas temperaturas de 20 e 25°C, combinadas com tempos de incubação 11, 14 e 21 dias. Os pré-inóculos utilizados foram Yeast Extrat Sucrose (YES) e Czapeck Yeast Extrat (CYA). Todas as cepas retiradas do pré-inóculo em meio YES e inoculadas no arroz, em temperatura de 25°C/18 dias e 20°C/14 dias, produziram aflatoxina B1. O meio CYA apresentou menor desempenho, uma vez que as três cepas testadas não produziram aflatoxina B1 na combinação 20°C/14 dias. A 25°C/11 dias de incubação a aflatoxina B1 não foi detectada.

RESUMO

The metals bioaccumulation in microganisms is mainly a result of superficial phenomena, occurring adsoption, in a stoychometric way, with the anionic radicals of cellular walls followed or not by precipitation of metals. To study the sorption of metals by live bacteria, the Cu2+ and Mn2+ taken up by a Bacillus sp. and a Pseudomonas sp., were quantified isolated from weath rizosphere, from a cloride solution of metals resting in the supernatant, after centrifugation. A completely randomized experimental design was used, with 3 repetitions. The effect of Cu2+ and Mn2+ contents, pH and time of bacterial growth were tested. Bacillus sorbed more Cu2+ and Mn2+ than Pseudomonas in all concentrations of those metals. Cu2+ sorption by both bacteria showed more increase than Mn2+ with rising those metals content in the solution. Alteration of pH from 5,0 to 3,0 reduced the metal sorption. With 90 hour cultivation time, Pseudomonas showed more Cu2+ and Mn2+ sorption than with 16 hour cultivation time. The results agree with the colloids cations exchange phenomena.

A bioacumulação de metais por microrganismos se deve principalmente a fenômenos de superfície, ocorrendo adsorção, de forma estequiométrica, com os radicais aniônicos dos envoltórios celulares, seguido ou não de precipitação dos metais. Para estudar condicionantes da sorção de metais por bactérias vivas, quantificou-se o Cu2+ e Mn2+ retirados por um Bacillus sp. e uma Pseudomonas sp., isolados da rizosfera de trigo, de uma solução de cloreto dos metais, determinando-se a quantidade de metal restante no sobrenadante, após centrifugação. Usou-se delineamento experimental inteiramente casualizado, com três repetições. Ensaiaram-se efeito dos teores de Cu2+ e Mn2+, do pH e do tempo de crescimento bacteriano. O Bacillus sorveu mais Cu2+ e Mn2+ do que Pseudomonas. em todas as concentrações desses metais. A sorção de Cu2+ por ambas as bactérias apresentou maiores incrementos do que Mn2+ com aumento dos teores desses metais na solução. A alteração do pH 5,0 para 3,0 diminuiu a sorção dos dois metais. Com o tempo de cultivo de 90 horas a Pseudomonas apresentou maior sorção de cobre e de manganês do que no tempo de 16 horas. Os resultados obtidos assemelham-se aos fenômenos de troca de cátions em colóides.

RESUMO

The metals bioaccumulation in microganisms is mainly a result of superficial phenomena, occurring adsoption, in a stoychometric way, with the anionic radicals of cellular walls followed or not by precipitation of metals. To study the sorption of metals by live bacteria, the Cu2+ and Mn2+ taken up by a Bacillus sp. and a Pseudomonas sp., were quantified isolated from weath rizosphere, from a cloride solution of metals resting in the supernatant, after centrifugation. A completely randomized experimental design was used, with 3 repetitions. The effect of Cu2+ and Mn2+ contents, pH and time of bacterial growth were tested. Bacillus sorbed more Cu2+ and Mn2+ than Pseudomonas in all concentrations of those metals. Cu2+ sorption by both bacteria showed more increase than Mn2+ with rising those metals content in the solution. Alteration of pH from 5,0 to 3,0 reduced the metal sorption. With 90 hour cultivation time, Pseudomonas showed more Cu2+ and Mn2+ sorption than with 16 hour cultivation time. The results agree with the colloids cations exchange phenomena.

A bioacumulação de metais por microrganismos se deve principalmente a fenômenos de superfície, ocorrendo adsorção, de forma estequiométrica, com os radicais aniônicos dos envoltórios celulares, seguido ou não de precipitação dos metais. Para estudar condicionantes da sorção de metais por bactérias vivas, quantificou-se o Cu2+ e Mn2+ retirados por um Bacillus sp. e uma Pseudomonas sp., isolados da rizosfera de trigo, de uma solução de cloreto dos metais, determinando-se a quantidade de metal restante no sobrenadante, após centrifugação. Usou-se delineamento experimental inteiramente casualizado, com três repetições. Ensaiaram-se efeito dos teores de Cu2+ e Mn2+, do pH e do tempo de crescimento bacteriano. O Bacillus sorveu mais Cu2+ e Mn2+ do que Pseudomonas. em todas as concentrações desses metais. A sorção de Cu2+ por ambas as bactérias apresentou maiores incrementos do que Mn2+ com aumento dos teores desses metais na solução. A alteração do pH 5,0 para 3,0 diminuiu a sorção dos dois metais. Com o tempo de cultivo de 90 horas a Pseudomonas apresentou maior sorção de cobre e de manganês do que no tempo de 16 horas. Os resultados obtidos assemelham-se aos fenômenos de troca de cátions em colóides.