Electrofermentation of food waste - Regulating acidogenesis towards enhanced volatile fatty acids production

Electrofermentation (EF) was used to overcome the thermodynamic limitations of conventional microbial fermentation and regulate the metabolism towards specific biobased products synthesis. Three single chambered EF systems (Applied potential (AP: -0.6 V), Closed circuit (CC: 100 Omega), Control (C)) were individually operated using composite canteen based food waste (FW) (COD-10 g/l) to comparatively analyze the effect of electrical stimulation on enhancing rate of fermentation. The total volatile fatty acids (VFA) showed higher production in AP (4595 mg/l) when compared to CC (3593 mg/l) and C (2666 mg/l). Fatty acid profiles (C-2-C-4) with individual compositions showed higher amount of acetic acid (C-2: H-Ac) followed by butyric acid (C-4: H-Bu) and propionic acid (C-3: H-Pr). AP showed higher amount of C-2: H-Ac (3221 mg/l) followed by C-4: HBu (900 mg/l) and C-3: HPr (474 mg/l), while CC showed higher C-2: HAc (2332 mg/l) followed by C-4: HBu (1233 mg/l) and C3: HPr (388 mg/l) when compared to C which showed higher C-2: H-Ac (1422 mg/l) followed by C-4-H-Bu (655 mg/l) and C-3-H-Pr (589 mg/l). Co-generation of biogas was higher in AP [bioH(2) (26%) and bioCH(4) (4%)] followed by CC [bioH(2) (22%) and bioCH(4) (1.3%)] and C [bioH(2) (11%) and bioCH(4) (6%)]. Fermentation induced with electron flux mechanism depicted the ability to elongate the chain length. Electrochemical characterization showed distinct disparity in electron transfer rates (K-app) along with waste remediation. The inferences concluded the key role of electrical stimulation on fermentation to enhance the conversion of conventional substrates to targeted carboxylic acids. Biohythane, an alternate renewable biofuel was also produced when bioH2 and bioCH4 are mixed in appropriate ratios. EF is an emerging technology that could open new frontiers in waste biorefinery by integrating bioprocesses for platform chemicals production through sustainable microbial electrochemical technologies.