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• Mn(III) associated with the surface of MnO 2 contributes to BPA degradation. • Mn(III)- and MnO 2 -mediated degradation of BPA differ mechanistically. • Mechanistic differences lead to products with distinct toxicological profiles. • Mn(III)-mediated BPA degradation should be considered in natural attenuation assessments. Bisphenol A (BPA) is a high production volume chemical with potential estrogenic effects susceptible to abiotic degradation by MnO 2. BPA transformation products and reaction mechanisms with MnO 2 have been investigated, but detailed process understanding of Mn(III)-mediated degradation has not been attained. Rapid consumption of BPA occurred in batch reaction vessels with 1 mM Mn(III) and 63.9 ± 0.7% of 1.76 ± 0.02 μmol BPA was degraded in 1 hour at circumneutral pH. BPA was consumed at 1.86 ± 0.09-fold higher rates in vessels with synthetic MnO 2 comprising approximately 13 mol% surface-associated Mn(III) versus surface-Mn(III)-free MnO 2 , and 10–35% of BPA transformation could be attributed to Mn(III) during the initial 10-min reaction phase. High-resolution tandem mass spectrometry (HRMS/MS) analysis detected eight transformation intermediates in reactions with Mn(III), and quantum calculations proposed 14 BPA degradation products, nine of which had not been observed during MnO 2 -mediated BPA degradation, suggesting mechanistic differences between Mn(III)- versus MnO 2 -mediated BPA degradation. The findings demonstrate that both Mn(III) and Mn(IV) can effectively degrade BPA and indicate that surface-associated Mn(III) increases the reactivity of synthetic MnO 2 , offering opportunities for engineering more reactive oxidized Mn species for BPA removal. [Display omitted] [ABSTRACT FROM AUTHOR]

Bisphenol A (BPA), a chemical of environmental concern, is recalcitrant under anoxic conditions, but is susceptible to oxidative degradation by manganese(IV)-oxide (MnO 2). Microbial Mn(II)-oxidation generates MnO 2-bio ; however, BPA degradation in cultures of Mn(II)-oxidizing bacteria has not been explored. We assessed MnO 2-bio -mediated BPA degradation using three Mn(II)-oxidizing bacteria, Roseobacter sp. AzwK-3b, Erythrobacter sp. SD-21, and Pseudomonas putida GB-1. In cultures of all three strains, enhanced BPA degradation was evident in the presence of Mn(II) compared to replicate incubations without Mn(II), suggesting MnO 2-bio mediated BPA degradation. Increased Mn(II) concentrations up to 100 µM resulted in more MnO 2-bio formation but the highest BPA degradation rates were observed with 10 µM Mn(II). Compared to abiotic BPA degradation with 10 μM synthetic MnO 2 , live cultures of strain GB-1 amended with 10 μM Mn(II) consumed 9-fold more BPA at about 5-fold higher rates. Growth of strain AzwK-3b was sensitive to BPA and the organism showed increased tolerance against BPA in the presence of Mn(II), suggesting MnO 2-bio alleviated the inhibition by mediating BPA degradation. The findings demonstrate that Mn(II)-oxidizing bacteria contribute to BPA degradation but organism-specific differences exist, and for biologically-mediated-abiotic-degradation (BMAD), Mn-flux, rather than the absolute amount of MnO 2-bio , is the key determinant for oxidation activity. [Display omitted] • MOB mediate enhanced BPA degradation at low (μM range) Mn(II) concentrations. • MOB contribute to BPA degradation, but organism-specific differences exist. • Mn flux determines efficacy of coupled biotic-abiotic BPA degradation. • Oxic-anoxic interfaces are hotspot barriers for BPA degradation. • The BMAD process, both natural and engineered, promises sustainable attenuation of BPA. [ABSTRACT FROM AUTHOR]

Polymorphs of MnO 2 comprise Mn(III) and Mn(IV), which are both strong oxidants capable of BPA degradation, but their relative contributions are unclear. To advance process understanding, the reactivities of biogenic MnO 2 prepared using Roseobacter sp. AzwK-3b and synthetic MnO 2 (i.e., hexagonal and triclinic birnessite) toward BPA were compared. Both colloidal and particulate biogenic MnO 2 , as well as triclinic birnessite, showed insignificant reactivity towards BPA, but degradation did occur when pyrophosphate (PP), a ligand for Mn(III), was present. Despite higher Mn(III) content of triclinic birnessite (38.6 %), only hexagonal birnessite with an Mn(III) content of 30.4 % degraded BPA without PP, and no rate increases were observed following the addition of PP. Similarly, colloidal MnO 2 degraded BPA with nearly double the rate measured with particulate MnO 2 (i.e., 1.24 ± 0.10 versus 0.73 ± 0.08 h−1), even though the Mn(III) contents were only 10 % different. The Mn(III) release rates from each MnO 2 polymorph in the presence of PP correlated more strongly with the observed BPA degradation rates than with Mn(III) content, suggesting that both Mn(III) release rate and Mn(III) content govern MnO 2 -mediated BPA degradation. In natural settings, Mn(III) generally occurs in complexed form suggesting that laboratory testing should include ligands to derive environmentally relevant information about MnO 2 -mediated degradation of BPA and other compounds of concern. [Display omitted] • Complexed Mn(III) contributes to the reactivity of MnO 2 polymorphs. • BPA degradation by biogenic MnO 2 and triclinic birnessite requires a ligand. • Mn(III) content and release rate govern MnO 2 reactivity. • Without ligand(s), MnO 2 reactivity will be underestimated. • MnO 2 -mediated degradation should be assessed in the presence of ligands. [ABSTRACT FROM AUTHOR]