@article{doydora_baars_cubeta_duckworth_urbieta_castro_2024, title={Using Manganese Oxidizing Fungi to Recover Metals from Electronic Waste}, volume={14}, ISSN={["2075-163X"]}, url={https://www.mdpi.com/2075-163X/14/1/111}, DOI={10.3390/min14010111}, abstractNote={Discarded electronic materials (e-waste) contain economically valuable metals that can be hazardous to people and the environment. Current e-waste recycling approaches involve either energy-intensive smelting or bioleaching processes that capture metals in their dissolved forms. Our study aimed to use Mn oxidizing fungi for recovering metals from e-waste that could potentially transform recycled metals directly into solid forms. We hypothesized that Mn oxidizing fungi can extract metals through chelation by siderophores and subsequent metal (or metal-chelate) adsorption to Mn oxides produced by fungi. Pure cultures of the three fungal species examined were grown on solidified Leptothrix medium with or without ground lithium ion batteries and incubated under ambient room temperature. The results showed Mn and Co were recovered at the highest concentrations of 8.45% and 1.75%, respectively, when grown with Paraconiothyrium brasiliensis, whereas the greatest concentration of Cu was extracted by Paraphaeosphaeria sporulosa at 20.6% per weight of e-waste-derived metals. Although metal-siderophore complexes were detected in the fungal growth medium, metal speciation data suggested that these complexes only occurred with Fe. This observation suggests that reactions other than complexation with siderophores likely solubilized e-waste metals. Elemental mapping, particularly of P. brasiliensis structures, showed a close association between Mn and Co, suggesting potential adsorption or (co)precipitation of these two metals near fungal mycelium. These findings provide experimental evidence for the potential use of Mn oxidizing fungi in recycling and transforming e-waste metals into solid biominerals. However, optimizing fungal growth conditions with e-waste is needed to improve the efficiency of metal recovery.}, number={1}, journal={MINERALS}, author={Doydora, Sarah A. and Baars, Oliver and Cubeta, Marc A. and Duckworth, Owen W. and Urbieta, Maria Sofia and Castro, Laura}, year={2024}, month={Jan} }
 @article{doydora_baars_harrington_duckworth_2021, title={Salicylate coordination in metal-protochelin complexes}, volume={11}, ISSN={["1572-8773"]}, DOI={10.1007/s10534-021-00352-7}, abstractNote={Molybdenum (Mo) is an essential trace element for bacteria that is utilized in myriad metalloenzymes that directly couple to the biogeochemical cycling of nitrogen, sulfur, and carbon. In particular, Mo is found in the most common nitrogenase enzyme, and the scarcity and low bioavailability of Mo in soil may be a critical factor that contributes to the limitation of nitrogen fixation in forests and agroenvironments. To overcome this scarcity, microbes produce exudates that specifically chelate scarce metals, promoting their solubilization and uptake. Here, we have determined the structure and stability constants of Mo bound by protochelin, a siderophore produced by bacteria under Mo-depleted conditions. Spectrophotometric titration spectra indicated a coordination shift from a catecholate to salicylate binding mode for Mo VI -protochelin (Mo-Proto) complexes at pH < 5. pKa values obtained from analysis of titrations were 4.8 ± 0.3 for Mo VI O 2 H 3 Proto -  and 3.3 ± 0.1 for Mo VI O 2 H 4 Proto. The occurrence of negatively charged Mo-Proto complexes at pH 6 was also confirmed by mass spectrometry. K-edge Extended X-ray absorption fine structure spectroscopy confirmed the change in Mo coordination at low pH, and structural fitting provides insights into the physical architecture of complexes at neutral and acidic pH. These findings suggest that Mo can be chelated by protochelin across a wide environmental pH range, with a coordination shift occurring at pH < 5. This chelation and associated coordination shift may impact biological availability and mineral surface retention of Mo under acidic conditions.}, journal={BIOMETALS}, author={Doydora, Sarah A. and Baars, Oliver and Harrington, James M. and Duckworth, Owen W.}, year={2021}, month={Nov} }
 @article{doydora_thompson_hesterberg_2020, title={Phosphate solubilization from adsorbents and precipitates by different AVAIL polymers}, volume={84}, ISSN={["1435-0661"]}, DOI={10.1002/saj2.20168}, abstractNote={AbstractLess than 40% of phosphate fertilizer applied to soils is typically taken up by the intended crop within the year of application because of strong soil retention. AVAIL polymers are fertilizer additives that were commercially developed to enhance availability of fertilizer phosphate. Knowledge of underlying mechanisms of phosphate solubilization would help to optimize the effectiveness of these polymers for different soils. This study compared different types and levels of AVAIL polymers in solubilizing (ad)sorbed and precipitated phosphate to gain insights into the mechanisms involved. Varying inputs of four newer forms of polymers and the original AVAIL (Original) were co‐reacted with one level of phosphate (ad)sorbed on ferrihydrite or noncrystalline Al hydroxide in batch (ad)sorption experiments or with Fe and Ca phosphate precipitates in dissolution experiments. Dissolved phosphate increased with increasing levels of co‐added polymers reacted with (ad)sorbents or phosphate precipitates. Across input levels evaluated, the Original AVAIL generally solubilized more phosphate from ferrihydrite than any of the new formulations. The Original and the new Liquid 2 formulation equally solubilized the greatest phosphate from Fe phosphate, whereas Liquid 2 solubilized more phosphate from Al hydroxide and Ca phosphate. (Ad)sorption and dissolution results implied competitive (ad)sorption and complexometric dissolution as key mechanisms. Our results suggest that the effectiveness of AVAIL polymers in soils depends on the level of added polymer charge relative to phosphate adsorption capacities or the types of phosphate minerals present.}, number={6}, journal={SOIL SCIENCE SOCIETY OF AMERICA JOURNAL}, author={Doydora, Sarah and Thompson, Margaret and Hesterberg, Dean}, year={2020}, month={Nov}, pages={1833–1845} }
 @article{doydora_hesterberg_klysubun_2017, title={Phosphate Solubilization from Poorly Crystalline Iron and Aluminum Hydroxides by AVAIL Copolymer}, volume={81}, ISSN={["1435-0661"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85014520924&partnerID=MN8TOARS}, DOI={10.2136/sssaj2016.08.0247}, abstractNote={
Core Ideas
Dissolved P increased with increasing co‐additions of AVAIL and P to metal oxides.
AVAIL dissolved greater P with Al‐hydroxide than with ferrihydrite.
AVAIL had no effect on P bonding distribution between Al(III) and Fe(III) in mixed sorbents.
Less than 40% of fertilizer phosphate applied to soils is generally taken up by crops because of strong retention of P by soil solids. Our objective was to determine mechanisms by which AVAIL, a maleic‐itaconic copolymer used as a fertilizer additive, potentially affects retention of applied phosphate, and consequently plant availability. We measured competitive sorption of AVAIL and orthophosphate in aqueous suspensions of ferrihydrite and poorly crystalline Al hydroxide [pxl‐Al(OH)3] at pH 6.2, and characterized phosphate bonding distribution between Fe(III) and Al(III) in 1:1 (w/w) mixtures of these solids using P K‐edge X‐ray absorption near edge structure (XANES) spectroscopy. With increasing co‐additions of AVAIL and P at the levels evaluated, sorption results showed dissolved P increasing up to 0.45 and 1.25 mM for ferrihydrite and pxl‐Al(OH)3, respectively, which represented 18 and 34% of added P. Negative relationships between sorbed P and sorbed AVAIL implied a competitive adsorption mechanism between these two ligands, and solubilization of Fe by AVAIL indicated complexometric dissolution of ferrihydrite. The XANES results showed that 72 to 86% of sorbed P was bonded with Al(III) in the ferrihydrite/pxl‐Al(OH)3 mixtures, with only a minor (<15%) effect of AVAIL apparent when P was applied at the two levels tested in this study. Our results suggest that optimized AVAIL application rates for enhancing crop availability of P would depend on soil sorption characteristics and the soil content of residual P relative to its soil sorption capacity.}, number={1}, journal={SOIL SCIENCE SOCIETY OF AMERICA JOURNAL}, author={Doydora, Sarah and Hesterberg, Dean and Klysubun, Wantana}, year={2017}, pages={20–28} }