Degradation of Metsulfuron Methyl by Agaricus blazei Murrill Spent Compost Enzymes

Metsulfuron methyl (MM) is an herbicide used in cereal crops. The white rot mushroom Agaricus blazei Murrill is an important edible and medicinal mushroom reported to be a major laccase producer, a lignin-degrading enzyme with low substrate specificity. A search for assaying the potential use of A. blazei spent mushroom compost (SMC) as a remediation tool for cleaning MM polluted soils was carried out. A phytotoxic dose of this herbicide was separately incubated with two enzyme preparations obtained from the SMC after the second mushroom fruiting flush; the phytotoxicity of the resulting reaction mixtures was then assayed by using a plantlet growing test with Brassica napus L. Thus, the crude enzyme SMC extract preparation (I) or the partially purified enzyme SMC extract (II) and their dilutions, 1:10 and 1:100, were mixed with MM (5 × 10^?3 ppm final concentration) and incubated at 25°C for 24, 48, 72, and 96 h. Plantlets separately exposed for 72 and 96 h to the resulting reaction mixtures between MM and those enzyme preparations showed a highly significant increase in their hypocotyl length with respect to plantlets exposed to MM alone. It was thus demonstrated the ability that complex enzyme fractions present in A. blazei SMC have to degrade MM during the right incubation time to compounds with no or lower phytotoxicity than this herbicide.