Novel fungal organophosphorus hydrolases in acidic media: an application to apples decontamination.

Organophosphorus pesticides bring significant improvements in agriculture, but their toxicity causes environmental and health negative impacts. The aim of this work was the development of robust biocatalysts to be applied in bioremediation. Four fungi were evaluated as hydrolase sources capable of degrading organophosphorus pesticides: Aspergillus niger, Fusarium sp., Penicillium chrysogenum, and Penicillium nalgiovense. The hydrolysis rates of methyl paraoxon obtained under acidic conditions were in the range of 10 to 21 mg L-1 d-1, which is remarkable since most similar biocatalysts are active under alkaline conditions. Penicillium chrysogenum activity was outstanding, and it was selected to prepare, characterize, and study the applications of its enzymatic extract. It was used to evaluate the bioremediation of apple surfaces at pH 2 in the presence of SDS, achieving complete methyl paraoxon degradation under proposed conditions. These results indicate that this biocatalyst could complement industrialized fruit washing processes for the elimination of organophosphorus pesticides.

Organophosphorus compounds biodegradation by novel bacterial isolates and their potential application in bioremediation of contaminated water.

Organophosphorus compounds (OPs), the major pesticides used worldwide, comprise an environmental hazard due to their harmful toxicity. Aimed to develop a bioreactor to remediate OPs contaminated wastewater, bacteria isolated from contaminated soils were identified and their ability to degrade OPs assessed, resulting in two main isolates, Sphingomonas sp. and Brevundimonas sp. Their OP degrading activities were characterized in terms of temperature, pH and substrates acceptance, resulting in high degradation rates at 60 °C, pH 10 and towards bulky OPs such as coroxon, coumaphos, and chlorpyrifos. Sphingomonas sp. cells were immobilized and 75.4% degradation of 0.15 mM chlorpyrifos was achieved after 21 days by immobilized cells in batch system, while this OP was completely degraded within 17 h when the biocatalyst is settled in a packed bed bioreactor, with a reusability of 8 cycles. These results suggest the potential application of this system in the bioremediation of contaminated wastewater.

Biocatalysed halogenation of nucleobase analogues.

The synthesis of halogenated nucleosides and nucleobases is of interest due to their chemical and pharmacological applications. Herein, the enzymatic halogenation of nucleobases and analogues catalysed by microorganisms and by chloroperoxidase from Caldariomyces fumago has been studied. This latter enzyme catalysed the chlorination and bromination of indoline and uracil. Pseudomonas, Citrobacter, Aeromonas, Streptomyces, Xanthomonas, and Bacillus genera catalysed the chlorination and/or bromination of indole and indoline. Different products were obtained depending on the substrate, the biocatalyst and the halide used. In particular, 85% conversion from indole to 5-bromoindole was achieved using Streptomyces cetonii.