Bioelectrocatalytical detection of H2O2 with different forms of horseradish peroxidase directly adsorbed at polycrystalline silver and gold

The bioelectrocatalytical reduction of H2O2 based on direct electron transfer (ET) between polycrystalline silver and the heme containing active site of horseradish peroxidase (HRP) is studied and compared with that obtained at gold. Native HRP and recombinant wild type HRP, containing additionally a six-histidine tag at the N-terminus, NHisrHRP, have been used for adsorptive modification of the electrodes. The histidine sequences, introduced into the peroxidase structure by genetic engineering of recombinant HRP using an E. coli expression system, were supposed to affect adsorption/orientation of the enzyme at the electrode surface. The variations in direct ET efficiency when changing from gold to silver, as well as from native HRP to NHisrHRP are analyzed and discussed, specifically, the high ET rates obtained with NHisrHRP-modified preoxidized gold and silver electrodes, though accompanied by extremely rapid loss of the biolectrocatalytical activity of the latter (silver) in direct (but not mediated) ET. The advantages and drawbacks of the studied HRP-electrode systems for the electroanalytical detection of H2O2 are considered

Cytotoxicity and mycotoxin production of shellfish‐derived <em>Penicillium</em> spp., a risk for shellfish consumers

In order to assess the putative toxigenic risk associated with the presence of fungal strains in shellfish-farming areas, Penicillium strains were isolated from bivalve molluscs and from the surrounding environment, and the influence of the sample origin on the cytotoxicity of the extracts was evaluated. Extracts obtained from shellfish-derived Penicillia exhibited higher cytotoxicity than the others. Ten of these strains were grown on various media including a medium based on mussel extract (Mytilus edulis), mussel flesh-based medium (MES), to study the influence of the mussel flesh on the production of cytotoxic compounds. The MES host-derived medium was created substituting the yeast extract of YES medium by an aqueous extract of mussel tissues, with other constituent identical to YES medium. When shellfish-derived strains of fungi were grown on MES medium, extracts were found to be more cytotoxic than on the YES medium for some of the strains. HPLC-UV/DAD-MS/MS dereplication of extracts from Penicillium marinum and P. restrictum strains grown on MES medium showed the enhancement of the production of some cytotoxic compounds. The mycotoxin patulin was detected in some P. antarcticum extracts, and its presence seemed to be related to their cytotoxicity. Thus, the enhancement of the toxicity of extracts obtained from shellfish-derived Penicillium strains grown on a host-derived medium, and the production of metabolites such as patulin suggests that a survey of mycotoxins in edible shellfish should be considered