Valorization of lignin to obtain platform chemicals via bio-electrochemical systems: batch and fed-batch mode analysis

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 H2O2, 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 H2O2 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 H2O2 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 H2O2, 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. (c) 2023 Society of Chemical Industry (SCI).

Automated summary

This study analyzes the batch and fed-batch mode of the microbial peroxide-producing cell (MPPC) for lignin valorization. The results show that the fed-batch mode is more productive in converting lignin into high-value platform chemicals.