Metagenomics Analysis for Improving Microbial Fuel Cells Performance for Treating Canned Pineapple Factory Wastewater

Microbial fuel cells (MFCs) are innovative and eco-friendly technologies supporting a circular economy by enabling the conversion of both organic and inorganic substances in wastewater to electricity. While conceptually promising, several challenges exist regarding the performance and stability of MFCs in real industrial settings. To address the gap, this work investigated the influence of specific operational settings regarding the hydraulic retention time (HRT) by varying HRT for 2 days and 4 days and organic loading rate (OLR) based on both low and high seasonal production on the performance of MFCs used for treating sulfide-rich wastewater from a canned pineapple factory. Through optimization, a current density generation of 47±15 mA/m2, a COD removal efficiency of 91±9%, and a sulfide removal efficiency of 86±10% were achieved. To reveal the microbial community within the MFC reactor as a key biological engine determining the overall MFC performance, including electricity generation and sulfide removal, microbiome analysis using a metagenomic approach was performed. A total of 14 samples, including inoculum sludge, anaerobically treated pineapple wastewater as the MFC influent, and anode-attached at the inlet, middle, and outlet points, and pooled suspended in each MFC reactor under three operating conditions, namely M1L, M2L, and M2H were collected for DNA extraction and 16S rRNA gene amplicon sequencing using the Illumina HiSeq platform with 2 x 250 bp paired-end sequencing. Based on amplicon sequencing, differential microbial abundance, and microbial association analysis, MFCsupporting microbes were identified to sustain MFC performance. This includes maintaining a high composition of electrogenic bacteria (i.e., Clostridium (OTU00515)), sulfide-oxidizing bacteria (i.e., Hydrogenophilaceae (OTU00713 and OTU01182), Candidatus Chlorothrix (OTU01036)), and methanotrophs (i.e., Methylocaldum (OTU00318 and OTU00322), Candidatus Methylospira (OTU00717)), while limiting the activity of sulfate-reducing bacteria (i.e., Acinetobacter (OTU00138)) and methanogens (i.e., Methanolinea and Methanosaeta) throughout the operation. Understanding the relationship between MFC performance and microbial activity helps in identifying the essential operating adjustments to maximize MFC performance in real industrial environments.