Ability of mixed fungal cultures to remove glyphosate from soil microcosms under stressful conditions

Abstract

Many herbicides used extensively to manage weeds and protect economically important crops contain glyphosate (GP) as their main ingredient, which contaminates ecosystems when it spreads from the soil into the surrounding environment. This study evaluated the ability of two fungal strains to remove GP at a microcosm scale. The strains, Aspergillus oryzae AM2 and Mucor circinelloides 166, were tested on their own and in mixed cultures. The microcosms were conditioned at 30 or 70% field capacity (FC), and contaminated with 5000 or 15,000 mg kg⁻¹ GP. The native microbial communities played a crucial role in the dissipation of the herbicide. At the end of the incubation (60 days), they had achieved removal percentages above 95% in most treatments. The exceptions were the microcosms subjected to hydric stress (30% FC) and contaminated with 15,000 mg kg⁻¹ GP, in which the co-cultures outperformed the native microbial species (≥ 80 vs 33% removal, respectively). An increase in AMPA (aminomethylphosphonic acid), the main metabolite of GP degradation, was usually detected after 60 days, which indicates that biodegradation may have been one of the main mechanisms involved in the removal of the herbicide. These results provide information about the potential of two mixed fungal cultures (containing species that are native to agricultural soils) to remove GP under stressful conditions.