Acid phosphatase synthesis in Aspergillus flavus

Fungal utilization of organophosphate pesticides and their degradation by Aspergillus flavus and A. sydowii in soil

Fungal species were isolated which utilize organophosphate pesticides, viz. phosphorothioic (pirimiphos-methyl and pyrazophos), phosphorodithioic (dimethoate and malathion), phosphonic (lancer) and phosphoric (profenfos) acid derivatives. Pesticide degradation was studied in vitro and in vivo (soil). Aspergillus flavus, A. fumigatus, A. niger, A. sydowii, A. terreus, Emericella nidulans, Fusarium oxysporum and Penicillium chrysogenum were isolated from pesticide-treated wheat straw. The number of A. sydowii colonies was significantly promoted by 1 mmol/L pirimiphos-methyl, pyrazophos, lancer, dimethoate and malathion when used as phosphorus sources and by pirimiphos-methyl and pyrazophos when used as carbon sources. The number of A. flavus colonies increased with 0.5 mmol/L lancer and malathion used as the only carbon sources. A. sydowii, A. niger, A. flavus, E. nidulans and F. oxysporum grew on, and utilized, 5 pesticides as phosphorus source and showed more than 50% mass growth. A. sydowii, A. flavus and F. oxysporum phosphatase hydrolyzed the pesticides suggesting that these species are important pesticide degraders. A. sydowii produced higher amounts of the phosphatase than A. flavus and F. oxysporum. The enzyme was highly active against pyrazophos, lancer and malathion used as the only sources of organic phosphate. A. flavus and A. sydowii phosphatases efficiently hydrolyzed pesticides at 300 ppm in soil, the degradation at 1000 ppm was lower. Mineralization of 1000 ppm pesticides in soil amended with wheat straw was higher than in nonamended soil. All added pesticides except profenfos were degraded within 3 weeks. Lyophilized adapted biomass of A. flavus and A. sydowii could thus be used for field biodegradation of these pesticides.