Bioremediation of Fungicides by Spent Mushroom Substrate and Its Associated Microflora

Experiments were conducted both under in vitro and in situ conditions to determine the biodegradation potential of button mushroom spent substrate (SMS) and its dominating microbes (fungi and bacteria) for carbendazim and mancozeb, the commonly used agricultural fungicides. During 6 days of incubation at 30 +/- 2 degrees C under broth culture conditions, highest degradation of carbendazim (17.45%) was recorded with B-1 bacterial isolate, while highest degradation of mancozeb (18.05%) was recorded with Trichoderma sp. In fungicide pre-mixed sterilized SMS, highest degradation of carbendazim (100.00-66.50 mu g g(-1)) was recorded with mixed inoculum of Trichoderma sp. and Aspergillus sp., whereas highest degradation of mancozeb (100.00-50.50 mu g g(-1)) was with mixed inoculum of Trichoderma sp., Aspergillus sp. and B-I bacterial isolate in 15 days of incubation at 30 +/- 2 degrees C. All these microbes both individually as well as in different combinations grew well and produced extracellular lignolytic enzymes on SMS, which helped in fungicides degradation. Under in situ conditions, among three different proportions of SMS (10, 20 and 30%, w/w) mixed with fungicide pre-mixed soil (100 mu g g(-1) of soil), the degradation of carbendazim was highest in 30% SMS treatment, while for mancozeb it was in 20% SMS treatment. The residue levels of both fungicides decreased to half of their initial concentration after 1 month of SMS mixing.