Comparative effects of permanganate and hydrogen peroxide pretreatment on the bioavailability and bioconversion of Australian lignite coal

• Oxidative pretreatment produced soluble coal-derived organics for fungal metabolism. • H 2 O 2 yielded the highest cumulative CO 2 , while KMnO 4 produced faster early kinetics. • TOC increased after oxidation but declined substantially during fungal incubation. • 3D-EEM revealed oxidant-specific differences in humic- and aromatic-like signals. • Coupled CO 2 evolution and carbon removal confirmed enhanced coal bioconversion. Microbial conversion of coal depends largely on the accessibility of soluble organic substrates derived from the coal matrix. This study evaluated oxidative pretreatment and subsequent fungal degradation of Australian lignite using hydrogen peroxide (H 2 O 2 ) and potassium permanganate (KMnO 4 ), followed by biodegradation with Paecilomyces variotii . Coal was pretreated with each oxidant and the solubilized fractions were assessed for bioavailability in aerobic biometer assays, using carbon dioxide (CO 2 ) production as a quantitative indicator of microbial metabolism. Pretreatment with H 2 O 2 produced the highest cumulative CO 2 generation, reaching ∼2.17 mmoles. /g coal, whereas permanganate pretreatment exhibited lower total CO 2 but a faster initial production rate. Oxidation produced substantial pools of dissolved carbon, increasing total organic carbon (TOC) to 35.0 mg C/g coal with KMnO 4 and 88.1 mg C/g coal with H 2 O 2 . Following fungal incubation, TOC decreased to 6.2 and 33.3 mg C/g coal, corresponding to consumptions of 28.9 and 54.8 mg C/g coal, respectively. These declines coincided with CO 2 evolution, indicating that a significant fraction of the dissolved carbon was mineralized, while the remainder was likely incorporated into biomass or intermediates. Fluorescence excitation-emission matrix analysis revealed oxidant-specific differences in humic- and aromatic-like constituents that diminished after biological treatment. These results demonstrate that CO 2 generation coupled with TOC depletion provides direct evidence of coal bioconversion potential under these conditions.