Iodine Accumulation and Biovolatilization by Filamentous Fungi and Their Effects on Extracellular Organic Acids

This study investigates the accumulation, volatilization, and metabolic effects of two iodine species (iodide and iodate) in selected filamentous fungi. Six environmentally relevant fungal strains were cultivated under controlled conditions, and iodine distribution between biomass, culture medium, and volatilized fraction was quantified using ICP-MS. Additionally, changes in extracellular metabolite production were determined by capillary isotachophoresis. The results revealed pronounced species-specific differences in iodine transformation. Fusarium poae exhibited the highest accumulation capacity, reaching up to 409.5 mg·kg−1 dry weight, and showed the most efficient overall iodine uptake from the cultivation medium. In contrast, Alternaria tenuissima and Trichoderma viride demonstrated elevated volatilization rates, particularly under iodate treatment, indicating distinct transformation pathways. Exposure to iodine species also induced significant changes in extracellular organic acids production. Increased levels of acetate, succinate, and sorbate suggest that iodine affects fungal metabolic activity, likely through stress-related shifts in central carbon metabolism and redox balance. These findings demonstrate that filamentous fungi employ diverse strategies for iodine transformation, including accumulation, volatilization, and metabolic adaptation. The results highlight the important role of fungi in regulating iodine speciation and mobility and provide new insights into their contribution to the terrestrial iodine cycle.