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BACKGROUND: There is tremendous potential for reusing lignin, which is generally discarded as waste. This research analyses the batch and fed-batch mode of the microbial peroxide-producing cell (MPPC), a type of bio-electrochemical cell that produces H 2 O 2 , a potent green oxidant utilized in the oxidation of Kraft lignin to produce platform chemicals with simultaneous wastewater treatment.RESULTS: The batch mode MPPC had a total shelf life of 10 days, with a peak phase of 5 days and maximum H 2 O 2 of 9.7 ± 0.06 mmol L −1 , and voltage of 164 ± 0.021 mV. The intermittent nutrition feeding strategy of fed-batch MPPCs aided microbe metabolic reactions, extending the system's lifespan to 21 days with a maximum voltage of 294 ± 0.01 to 525 ± 0.008 mV and H 2 O 2 of 14.14 ± 0.12 to 32.96 ± 1.35 mmol L −1 , respectively. This offered more exposure time for lignin hydroxyl radical oxidation by H 2 O 2 , with enhanced depolymerization of 37-80% of high lignin concentration in repeated cycles compared to batch mode, which accomplished only 53.46%. Fourier transform infrared spectroscopy confirmed the structural changes in lignin of all systems, displaying loss and disorientation of major functional groups with greater intensity in fed batch-operated MPPCs. Platform chemicals with high commercial value, including guaiacol, ferulic acid, vanillin, and others, were identified using liquid chromatography-mass spectrometry. In terms of wastewater treatment, biochemical oxygen demand and chemical oxygen demand removal efficiency ranged from 59% to 83%, with fed-batch being the most efficient.CONCLUSION: This research suggests that fed-batch mode MPPC is significantly more productive than batch mode MPPC for lignin valorization to produce platform chemicals, making it more sustainable, economical, and environmentally friendly.

To boost growth and global competitiveness, a growing number of industries and sewage treatment plants are making “sustainability” and “cost‐effectiveness” key goals in their strategy and vision. This movement is also spreading far beyond the small group of people who recognize as “green”. This is the first study to demonstrate that domestic sewage water can be utilized as anodic feed for the electrochemical production of H2O2 in the catholyte with simultaneous wastewater treatment in a microbial peroxide‐producing cell (MPPC) designed cost‐effectively utilizing a variety of catholyte and few electrode materials. The electrochemical output utilizing domestic wastewater resulted in maximum production of 62 mM H2O2 in a 37‐day batch in the MPPC with 50 mM H2SO4 catholyte having a bare activated charcoal electrode. The constantly rising H2O2 production during the 37‐day hydraulic retention time demonstrated the system's sustainability and efficiency in contrast to other reported studies. Cyclic voltammetry analysis of the catholyte with the Fenton process showed excellent redox peaks, indicating its applicability for in‐situ pollutant degradation. The MPPCs had an overall 40%–60% and 65%–85% removal efficiency of biochemical oxygen demand and chemical oxygen demand. This study shows that a simple MPPC design with no extensive modifications can be efficient at producing H2O2 and simultaneously treating wastewater.

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Lignin is a potential renewable feedstock to produce value-added compounds, but the overwhelming bulk of it is either burned for energy or discarded as waste. This paper addressed two critical issues: waste-to-value generation and management by demonstrating the in situ depolymerization of lignin extracted from waste rice straw utilizing the microbial electro-Fenton process in a microbial peroxide-producing cell (MPPC), a type of bio-electrochemical cell, for value addition while synchronously treating wastewater. The MPPC electrochemical voltage yields of 0.171 ± 0.05–0.497 ± 0.2 V produced 9 ± 0.43–34 ± 0.11 mM of H2O2, which was utilized to depolymerize lignin at various concentrations. Interestingly, a direct correlation was observed between lignin depolymerization and H2O2 concentration, while Fourier-transform infrared spectroscopy data revealed a constant disruption of the lignin structure accurately in the wavenumber region of 1000–1750 cm–1 irrespective of the H2O2 concentration. Carboxylic acid derivatives, benzopyran, hexanoic acid, and other valuable compounds were detected in the LC QTOF MS data from the depolymerized lignin mixture. Remarkably, SEM analysis demonstrated morphological changes in depolymerized lignin induced by the oxidative effects of hydroxyl radicals. Biochemical oxygen demand and chemical oxygen demand removal was 60 ± 3–85 ± 1% in anodic wastewater treatment. This research provides a sustainable and efficient technique for lignin valorization and wastewater treatment.