Zn(II) sequestration by fungal biogenic manganese oxide through enzymatic and abiotic processes

Sequestration and Oxidation of Cr(III) by Fungal Mn Oxides with Mn(II) Oxidizing Activity

“…In contrast to very low oxidation efficiency, the cumulative C T seq concentration was high at 1.18 mM (0.43 ± 0.01, 0.46 ± 0.01, and 0.14 ± 0.00 mM for the 1st, 2nd, and 3rd treatments, respectively), corresponding to 83% ± 1% of the cumulative Cr III Int (Figure 7 and Table S2). The molar ratio of C T seq relative to solid Mn was abnormally high (~120 mol%), implying a sequestration mechanism specific to Cr other than the simple sorption process of common divalent heavy metal ions, Zn 2+ and Cd 2+ (their maximum sorption relative to solid Mn was 20-25 mol%; [39,41]) or trivalent La 3+ ions (~30 mol% [45]). Heated BMOs possessed similar Cr sequestration capacity ( Figure S3) even under aerobic conditions with the domination of Cr(III) in the solid phase, which was revealed by X-ray Absorption Near-Edge Structure (XANES) (Figure 8).…”

“…Cumulative Cr and Mn (mM) Newly formed BMOs produced by A. strictum KR21-2 are layered analogously to vernadite, a natural nanostructured and turbostratic variety of birnessite [32]. Prior to 0.5 mM Cr(NO 3 ) 3 treatments, no apparent changes in X-ray Diffraction (XRD) patterns were observed between newly formed and heated BMOs (Figure 9), for which the XRD peaks at~7.3, 2.4, and 1.4 Å were assigned to (001), (11,20), and (31,02), respectively [39]. Following the treatment, heated BMO exhibited a decline in XRD intensity arising from (001) basal reflection (Figure 9), suggesting that the ordering of the vernadite (birnessite) sheet stacking was mostly disturbed by sorption of polynuclear Cr(III) species with a high proportion of Cr T seq (0.42 ± 0.00 mM) relative to solid Mn (1 mM as Mn).…”

“…Acremonium strictum KR21-2, which is capable of enzymatically oxidizing Mn(II) to BMO [51,52], was grown in HAY liquid medium (20 mM 4-(2-hydroxyethyl)-1-piperazineethanesulphonic acid (HEPES) buffer (pH 7.0) with 1 mM MnSO 4 ) as reported previously [27,30,39,41].…”

Zinc Presence during Mineral Formation Affects the Sorptive Reactivity of Manganese Oxide

“…Manganese oxides (MnO x ), especially layered phyllomanganates, are important metal oxides in terrestrial and oceanic environments [1][2][3]. Because of the high surface area, negative surface charge, vacancy sites, and high oxidative potential, phyllomanganates have a strong tendency to interact with and strongly influence the fate and transport of trace metals, such as Ni [4][5][6][7][8], Co [6,[8][9][10][11][12][13], Pb [7,[14][15][16][17][18], Cu [6,19,20], Zn [4,7,17,[21][22][23], and Cd [24,25]. Phyllomanganates can interact with metals in different ways (e.g., sorption, coprecipitation, incorporation), which in turn can affect the property and reactivity of the host mineral phases.…”

“…The compatibility of foreign metal ions in birnessite layers is Fe 3+ < Ni 2+ < Co 3+ and the interruption of birnessite structures is in the reverse order Fe 3+ > Ni 2+ > Co 3+ [7,11,13]. Zn is an essential element and its biogeochemical cycles are affected by organic matters and Fe/Mn oxide minerals in soils and marine sediments [4,7,17,[21][22][23]33]. Zn shows the least compatibility with Mn oxides compared to other transition metals such as Ni or Co. As a result, upon sorption onto MnO x , Zn 2+ never incorporates into vacancy sites, but always exists as sorbed species above/below vacancy sites [27] and sometimes edge sites [34].…”