Accumulation and bio-oxidation of arsenite mediated by thermoacidophilic Cyanidiales: innate potential biomaterials toward arsenic remediation

[Display omitted] •Cyanidium caldarium (Cc) showed greatest As(III) sorption capacity (83.2 mg g−1).•Complexes of As(III)/As(V)-polysaccharide and As(III)-cysteine were found on cells.•No As(V) was detected within the Cyanidiales cells.•Arsenite was fixed by extracellular polysaccharides or transported into the cells.•New insights for Cyanidiales to bypass As(V) uptake, reduction, and methylation. Addressing geogenic and anthropogenic arsenic (As) pollution is critical for environmental health. This study explored arsenite [As(III)] removal using Cyanidiales, particularly Cyanidium caldarium (Cc) and Galdieria partita (Gp), under acidic to neutral pH, and determined As(III) detoxification mechanisms in relation to As speciation and protein secondary structure in Cyanidiales. Regarding As(III) sorption amounts, Cc outperformed Gp, reaching 83.2 mg g−1 of removal at pH 5.0. Wherein, 23.5 % of sorbed As on Cc presented as arsenate [As(V)] complexation with polysaccharides, alongside other predominant species including As(III)-cysteine (41.2 %) and As(III)-polysaccharides (35.3 %) complexes. This suggested that As(III) was directly transported into cells, rather than As(V). Coupled with the formation of As(III)-cysteine complexes within cells, these mechanisms may be key to efficiently accumulating As(III) in Cyanidiales during the 6-h incubation. These results highlight the potential of Cyanidiales for sustainable As(III) remediation and provide new insights into managing As(III) toxicity.