Determination of peracid and putative enzymatic peracid formation by an easy colorimetric assay

A sensitive and semi-quantitative colorimetric method for the determination of peracids in the presence of hydrogen peroxide in Luria-Bertani (LB) aga r is described. For this purpose the redox active ate-dye 2-methylsulfanyl- 4-(3-methylsulfanyl-phenylazo)-aniline for the visual detection of peracids was synthesized. The change in color is based on the exclusive oxidation o f methylsulfanyl-groups derived from peracids. Because of the lethal effect of hydrogen peroxide and peracids to microorganism and the degradation of hydrogen peroxide it was not possible to add the assay substances directly to the medium. Thus, we overlayed the medium with a soft agar. The assay sy stem was validated with peracetic acid, a mixture of tetraacetylethylene di amine (TAED) and hydrogen peroxide, as well as with the Lipase from Pseudom onas cepacia (PCL). A semi-quantitative relationship between the size of th e halo and the concentration of peracetic acid could be shown. With this as say it should be possible to discover enzymes or enzyme producing microorga nism, which are capable to form peracids in situ, (C) 1999 Elsevier Science B.V. All rights reserved.