Ascorbate-Promoted Whole-Cell Biocatalysis for Lithium Bio-Recovery from Spent LiFePO4 Cathodes

The sustainable recycling of spent lithium iron phosphate (LiFePO 4 ) batteries via bioleaching is critically important yet often constrained by low processing capacity and severe microbial oxidative stress. Herein, we report a highly efficient biocatalytic strategy utilizing Gluconobacter oxydans as a whole-cell biocatalyst for the leaching of spent LFP batteries. We demonstrate that the addition of 25 mM ascorbic acid (AA) dramatically enhances the catalytic performance of this microbial system, achieving a high lithium extraction yield of 92.7% within 7 days at a pulp density of 10.0 g L –1 . Transcriptomic and biochemical analyses elucidate a novel synergistic catalytic mechanism: AA not only alleviates intracellular oxidative stress to sustain microbial catalyst but also actively participates in a pyrroloquinoline quinone (PQQ)-mediated extracellular redox cycle. In this cycle, the reduction of PQQ by AA and its subsequent reoxidation by O 2 generate H 2 O 2 . Under mild acidic conditions (pH ∼4), these H 2 O 2 preferentially drive the catalytic oxidation of LiFePO 4 to FePO 4 , thereby significantly facilitating Li release. The dissolved Li was further recovered from bioleachate as Li 3 PO 4 , while the FePO 4 -rich residues showed effective dye–removal activity, demonstrating residue valorization potential. This work unveils the dual function of AA in fortifying the microbial catalyst and driving mineral oxidation, presenting a practical and economically viable strategy for the integrated recycling of spent LFP batteries.