Characterization of yeast strains isolated from agricultural soils for their potential in biodegradation of glyphosate

Glyphosate (GP) is the most used herbicide in agriculture. Its prolonged use has led to the frequent occurrence of GP and its main metabolite, AMPA, in the environment, posing risks to ecosystems and human health. Yeasts, due to their metabolic plasticity, represent promising candidates for soil bioremediation. This study aimed to isolate and characterize yeasts able to degrade GP and AMPA using them as nutritional source. Soil samples were collected from a wheat field with a history of GP use in Marsciano (PG), and isolation in enrichment condition with GP and AMPA as sole P source was carried out. Yeast strains were identified through molecular approach and will be deposited in the Culture Collection DBVPG of the University of Perugia. Out of 25 isolates, 17 were identified as the black yeast Exophiala alcalophila Goto & Sugiy (Herpotrichiellaceae). Screening in 96-wells plates were performed for all the strains in P-free mineral medium with GP or AMPA at 2.5, 5 and 10mM and growth was monitored by measuring OD600 twice daily for 7 days. Preliminary results showed different growth patterns among treatments. Most of E. alcalophila strains showed increased growth values at the highest AMPA concentration compared to the negative control (C-), which suggests their ability to use AMPA as P source. Moreover, since the growth value at 10 mM exceeded twice that of the positive control (C+), this may even stimulate yeast growth. However, the presence of GP reduced the performance of these strains. Instead, other strains not yet identified showed higher growth values with GP compared to C-, and reduced growth with AMPA. In conclusion, our results suggest that yeasts may degrade GP and AMPA, highlighting their potential for the bioremediation of GP- and AMPA-contaminated agricultural soils. Funded by: “INAIL-DIT, PAR 2022-2024, Ricerca Scientifica P8O7” & "Glyphosate mycoremediation of agricultural soils: a broad spectrum of nature-based solutions" (protocol no.RM123188F7AAFA9E)