Biomass to bioflavor: microbial electrochemical‐assisted depolymerization of lignin and recovery of vanillin

Abstract The sustainable production of vanillin, a high‐value bioflavor compound, from renewable feedstocks such as Kraft lignin (KL) is a key focus in biorefinery research. This study introduces a microbial electrochemical cell (MEC)‐assisted approach for KL depolymerization, integrating ultrafiltration and liquid–liquid extraction for efficient vanillin recovery. The MEC system has achieved chemical oxygen demand (COD) and biological oxygen demand (BOD) removal rates of 89% and 78%, respectively, while simultaneously generating power (224 ± 0.08 mV) and producing hydrogen peroxide (H 2 O 2 ) at 29.20 ± 0.39 mM to facilitate lignin oxidation. Fourier transform infrared analysis (FTIR) confirmed substantial lignin depolymerization, consistent with an 88% reduction in COD. Depolymerized lignin was effectively fractionated using ultrafiltration membranes, and vanillin was recovered via liquid–liquid extraction with 99% purity. The process reached a bioconversion efficiency of 16.9%, yielding 146 mg of vanillin per gram of KL. This approach highlights the potential of microbial electrochemical technologies to advance lignin valorization, supporting the transition to renewable chemical production and a circular bioeconomy, while providing additional functionalities such as bioenergy generation. The findings offer a pathway for scalable, eco‐friendly bioconversion of lignin into valuable bioproducts.