Biotransformation of sucrose into 5-hydroxy-2-hydroxymethyl-γ-pirone by Aspergillus flavus

Foram investigadas a hidrólise da sacarose e a preferência pela glicose frente à frutose no processo de produção do 5-hidroxi-2-hidroximetil-γ-pirona (HHMP) na presença de Aspergillus flavus IOC 3974 cultivado em meio líquido Czapeck. Quantidades de 0,5g de pelletes foram utilizadas como inóculo. Doze frascos cônicos de 250 ml contendo 100 ml de meio de cultura com diferentes concentrações de sacarose foram utilizados. Os microrganismos foram cultivados a 120 rpm e 28"C por 16 dias sem ajuste do pH. O maior rendimento do HHMP foi 26g l^-1 em 120g l^-1 de sacarose. Nestas condições, A. flavus, foi capaz de produzir uma invertase possibilitando a hidrólise de 65% da concentração total de sacarose em 24 horas, conjuntamente com a produção de uma isomerase que foi capaz de converter a frutose em glicose. Este trabalho está focalizado preferencialmente no consumo da glicose frente à frutose por A. flavus e na estratégia de produção do HHMP.

Biotransformation of chalcones by the endophytic fungus Aspergillus flavus isolated from Paspalum maritimum trin

O fungo Aspergillus flavus isolado como endofítico da planta Paspalum maritimum Trin. foi avaliado quanto ao seu potencial de aplicação em reações de biotransformações. Os compostos chalcona (1), 3,4,5-trimetoxichalcona (2) e 2,3,4,4'-tetrametoxichalcona (3) foram biotransformados, respectivamente, na diidrochalcona (4), 3,4,5-trimetoxidiidrochalcona (5) e 2,3,4,4'-tetrametoxidiidrochalcona (6). As estruturas destes compostos foram determinadas por análises de RMN uni e bidimensionais e por espectrometria de massas. As diidrochalconas 5 e 6 são substâncias inéditas.

Cytotoxicity and genotoxicity of low doses of mercury chloride and methylmercury chloride on human lymphocytes in vitro

Mercury is a xenobiotic metal that is a highly deleterious environmental pollutant. The biotransformation of mercury chloride (HgCl2) into methylmercury chloride (CH3HgCl) in aquatic environments is well-known and humans are exposed by consumption of contaminated fish, shellfish and algae. The objective of the present study was to determine the changes induced in vitro by two mercury compounds (HgCl2 and CH3HgCl) in cultured human lymphocytes. Short-term human leukocyte cultures from 10 healthy donors (5 females and 5 males) were set-up by adding drops of whole blood in complete medium. Cultures were separately and simultaneously treated with low doses (0.1 to 1000 µg/l) of HgCl2 and CH3HgCl and incubated at 37ºC for 48 h. Genotoxicity was assessed by chromosome aberrations and polyploid cells. Mitotic index was used as a measure of cytotoxicity. A significant increase (P < 0.05) in the relative frequency of chromosome aberrations was observed for all concentrations of CH3HgCl when compared to control, whether alone or in an evident sinergistic combination with HgCl2. The frequency of polyploid cells was also significantly increased (P < 0.05) when compared to control after exposure to all concentrations of CH3HgCl alone or in combination with HgCl2. CH3HgCl significantly decreased (P < 0.05) the mitotic index at 100 and 1000 µg/l alone, and at 1, 10, 100, and 1000 µg/l when combined with HgCl2, showing a synergistic cytotoxic effect. Our data showed that low concentrations of CH3HgCl might be cytotoxic/genotoxic. Such effects may indicate early cellular changes with possible biological consequences and should be considered in the preliminary evaluation of the risks of populations exposed in vivo to low doses of mercury.