16S rRNA amplicon sequencing of anaerobic biofilm microbial communities

Objective: This study aimed to elucidate the key physicochemical properties of conductive materials (CMs) governing anaerobic biofilm development and methanogenic metabolism.Method: Five carbon-based CMs with distinct pore structures were selected: macroporous Bamboo Biochar (BB) and Straw Biochar (SB), microporous Peach Shell Biochar (PSB) and Coconut Shell Biochar (CSB), and non-porous Granular Graphite (GG). The physical morphology and (electro-)chemical properties of CMs were comprehensively characterized. Anaerobic biofilm cultivation experiments were conducted using these CMs in particulate and powdered forms, followed by the evaluation of methanogenic performance and microbial community structure, and statistical analysis of correlations between carrier properties and biofilm functions.Results: In particulate-carrier experiments, BB and SB achieved similar highest methanogenic performance, followed by PSB and CSB, whose performances were also comparable, with GG being the least effective. When the pore structure was eliminated by ground into powder and fixed onto carbon paper, BB, SB, PSB, and CSB performed similarly, whereas GG then exhibited superior performance. Compared with other CMs, biofilms on microporous particulate-carrier (BB/SB) showed higher biomass, archaeal content, and protein-rich extracellular polymeric substances. The physical state of the carrier material shapes the biofilm's microbial community more strongly than the material type.