Carbon cloth stimulates direct interspecies electron transfer for phenol biodegradation

In this study, we investigated the effect of carbon cloth (CC) on the anaerobic process of phenol biodegradation, by stimulating direct interspecies electron transfer (DIET) combined with adsorption process. Phenol biodegradation was examined over three sequential batches using bioreactors consisting of 100 mL syringes. Three experiment sets with different types of activated carbon (AC) were examined. Addition of all types AC to the bioreactors significantly enhanced methane production rate (two-fold higher compared to control sets without AC).Adsorption isotherms and kinetics suggest that the enhancement of phenol biodegradation may occur through a synergetic adsorption-biodegradation process, where a significant and fast reduction of phenol adsorption contributes to decreasing the inhibition effect, followed by biological anaerobic digestion (AD) of the adsorbed phenol by stimulating DIET process. The optimal concentration for carbon cloth single weave (CCSW) promoted the DIET and adsorption processes. High-throughput sequencing of microbial communities revealed that CCSW facilitated the enrichment of syntrophic bacterial groups (Rikenellae, Syntrophorhabdaceae, Gracilibacteraceae, and DTU014), and also archaea (Methanosaetaceae and Methanosaetaceae), which are known to be key players in DIET processes and promote phenol degradation. This work demonstrates how CC stimulates DIET processes in anaerobic bioreactors, to enhance biodegradation of phenol at high concentration.