Neste estudo avaliou-se uma rota biológica à temperatura ambiente para a biotransformação da cinza da casca de arroz em nanopartículas de sílica empregando o fungo Fusarium oxysporum. Foram realizados ensaios e monitorou-se a produção de biomassa fúngica, pH e concentração de sílica solúvel em meio de cultura contendo cinza durante 270 h a uma temperatura de 25°C, com uma concentração inicial de biomassa de 0,3 g/L (base úmida) in situ. A cinza antes e após o tratamento foi analisada por espectroscopia de infravermelho IV; MEV e DRX. Os resultados deram indícios que com o processo biológico à temperatura ambiente ocorre uma biotransformação da cinza da casca de arroz, gerando sílica solúvel e cristalina no meio de cultura. Tais resultados indicam a possibilidade da síntese por via biológica de nanomateriais óxidos.

In this study a biological route at room temperature for the biotransformation of rice husk ash (RHA) in silica nanoparticles using the fungus Fusarium oxysporum was evaluated. Some tests were carried out by monitoring the fungal biomass production, pH, soluble silica on culture medium with rice husk ash and fungi, during 270 h at a 25°C temperature and 0.3 g/L (wet basis) biomass concentration, in situ. The RHA was analyzed before and after processing by SEM and XRD. The results indicated that trhrough a biological process at room temperature a biotransformation of rice husk ash is reached by bioleaching and enzymatic action allowing the synthesis of oxidic nanomaterials.

RESUMO A biodegradação dos efluentes de uma indústria de papel e celulose foi monitorada em relação aos parâmetros de fenóis totais, fenóis de baixa massa molar e cor durante a sua incubação com lacase (Novozymes), lacase-HBT e peroxidase (Merck). Os resultados revelaram que a lacase reduziu a cor do efluente em 37% e a peroxidase em 43%. Também foi possível observar que as enzimas possuiram grande eficiência na redução de cor, compostos fenólicos totais e compostos fenólicos de alta massa molar contidos no efluente, indicando, desta forma, que a despolimerização ocorreu.

ABSTRACT The biodegradation of effluent from an industrial paper mill was monitored in relation to the parameters total phenols, low molar mass phenols and color during its incubation with laccase (Novozymes), laccase-HBT and peroxidase (Merck). The results revealed that the laccase reduced the effluent color by 37% and the peroxidase by 43%. Also, the enzymes had a great efficiency in the reduction of color, total phenols and high molar mass compounds contained in the effluent, indicating that depolymerization occurred.

The livers of Geophagus brasiliensis collected from both a non-polluted site and a polluted site were analyzed for different antioxidant defenses, O2 consumption, thiobarbituric acid-reactive substance (TBARS) levels, and histological damage. Compared to controls (116.6 ± 26.1 nmol g-1), TBARS levels were enhanced at the polluted site (284.2 ± 25.6 nmol g-1), as also was oxygen consumption (86.6 ± 11.3 and 128.5 ± 9.8 µmol O2 min-1 g-1, respectively). With respect to enzymatic antioxidants, increased catalase activities (8.7 ± 1.3 and 29.2 ± 2.4 mmol min-1 g-1, respectively), unchanged superoxide dismutase activities (767.2 ± 113.3 and 563.3 ± 70.2 U g-1, respectively), and diminished glutathione S-transferase activities (29.0 ± 3.2 and 14.9 ± 3.2 µmol min-1 g-1, respectively) were detected. Reduced glutathione (1.91 ± 0.17 and 1.37 ± 0.25 mM, respectively), oxidized glutathione (1.50 ± 0.20 and 0.73 ± 0.17 mM, respectively), and total glutathione (3.40 ± 0.26 and 2.07 ± 0.27 mM, respectively) concentrations were also below control values at the polluted site. Nevertheless, the observed ethoxyresorufin-O-deethylase activities (1.34 ± 0.11 and 16.7 ± 0.21 pmol min-1 mg-1, respectively) showed enhanced values at the polluted site. The main histological damage observed in the hepatocytes from fish collected at the polluted site was characterized by heavy lipid infiltration. Fish collected at the end of spring showed higher O2 consumption, higher superoxide dismutase and glutathione S-transferase activities, and higher total and oxidized glutathione concentrations compared to the beginning of autumn. No seasonal changes were observed in catalase activities, glutathione or TBARS levels. Fish chronically exposed to relatively high pollution levels seem to be unable to set up adequate antioxidant defenses, probably due to severe injury to their hepatocytes. The higher antioxidant defenses found at the end of spring are probably related to the enhanced activities during high temperature periods in thermoconforming organisms.