A polylactic acid enclosure alleviates long-chain fatty-acid inhibition by stabilizing electroactive biofilms during anaerobic digestion of lipid-rich food waste

Description

Lipid-rich food waste has high biomethane potential, but long-chain fatty acids (LCFAs) released during hydrolysis inhibit syntrophic conversion and destabilize methane recovery. We tested whether a permeable polylactic acid (PLA)-filled enclosure around polarized electrodes could retain LCFA-stressed biomass and coordinate reducing-equivalent turnover. An unpowered PLA-enclosed electrode control (CK), polarized exposed-electrode microbial electrolysis cell-assisted digester (MEC), and polarized PLA-enclosed anode microbial electrolysis cell-assisted digester (PMEC) were compared using model fatty acids and staged lipid-loaded synthetic food waste. During oleate methanation, PMEC produced 144.8 NmL CH4/g-VS, 54.2% more than MEC. At a nominal added-oil loading of 140% relative to the initial inoculum VS, methane yield reached 464.1 NmL CH4/g-VS in PMEC, compared with 377.0 in MEC and 105.2 in CK. During the subsequent 60%–140% lipid challenge at 1.2–1.5 V, PMEC depleted volatile fatty acids more rapidly and sustained methanogenesis; its day-20 headspace was CH4-dominated. On day 20, PMEC retained 19.1 g of electrode-associated wet solids, 6.4-fold the MEC value, and exhibited greater extracellular redox capacity and electron-transport-system activity, stronger voltammetric responses, and lower apparent interfacial impedance. Metagenomic and metabolomic profiles were consistent with pathway-selective reorganization of lipid entry and electron routing rather than uniform enrichment of β-oxidation or terminal methanogenesis. Collectively, the enclosure established a biomass-retentive, redox-responsive polarized interface that improved coordination between LCFAs conversion and downstream electron consumption, supporting polarized microenvironment engineering as a strategy for stabilizing methane recovery from residual-oil food waste without increasing applied voltage.

Institutions

• Anhui Agricultural University

  Anhui, Hefei

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