Bioremediation potential of button mushroom spent substrate against cadmium and lead under pilot scale experimentation

Abstract

Spent substrate (SMS) from button mushroom (Agaricus bisporus) was evaluated for its bioremediation potential against two hazardous heavy metals (cadmium and lead) under in vitro and in vivo conditions. Presence of two heavy metals in cultural media reduced the fungal count by 1.5 to 400 folds in SMS. Out of three dominating fungi viz., Trichoderma sp., Aspergillus sp., and Blastomycetes sp., isolated from SMS, Aspergillus sp. exhibited highest bioremoval of cadmium and lead (60.80 and 69.21%) under cultural conditions. It was followed by Trichoderma sp. (55.30 and 58.65%) and least in control (38.50 and 41.89%). On sterilized button mushroom SMS, the removal of two heavy metals was almost 2 to 4 folds higher in microbes inoculated treatments compared to control. Compared to cadmium, lead was nearly 2 to 4 times less available at different stages of sampling. Out of different permutations and combinations of microbes, the mixed inoculum of Trichoderma sp., Aspergillus sp. and Mucor sp. exhibited highest bioaccumulation for cadmium and lead. Mixing of different proportions (10, 20 and 30%, w/w) of SMS in soil led to an increase in moisture retention capacity and porosity of soil, while it decreased the bulk density, however the effect was more pronounced in higher proportion of SMS (30%). Compared to control, the bioremoval of two heavy metals was higher in SMS amended soils and it was highest in soil received highest proportion of SMS (30%). Cadmium reached to near negligible level after 6 months of SMS mixing, while it took only 3 months in case of lead.