Impact of storage duration and method on cathodic microbiomes recovery.
Preserving mixed microbial communities remains a bottleneck for reproducibility and deployment of biotechnologies, including microbial electrosynthesis (MES), where cathodic communities reduce CO2 to acetate. We assessed how preservation method and storage duration shape biocathode recovery. Cathodic biomass enriched for 44 days was preserved by freezing without cryoprotectant, freezing with glycerol, or lyophilization with a maltodextrin–trehalose stabilizer, stored for 39 or 174 days, and reactivated for 85–90 days. Storage duration, not preservation method, dominated recovery: current density and acetate production were threefold higher after 39 days than after 174 days, and coulombic efficiency fell from 75% to 43%. Short-term storage preserved an Acetobacterium-dominated community correlated with acetate production (R² = 0.8), whereas prolonged storage led to its near-loss and a more diverse but functionally diffuse assemblage, with Wood–Ljungdahl potential redistributed across Sporomusa-affiliated genomes alongside enriched sporulation functions. Storage duration therefore appears to act as a selective temporal filter favoring dormancy-competent lineages.
Preserving mixed microbial communities remains a bottleneck for reproducibility and deployment of biotechnologies, including microbial electrosynthesis (MES), where cathodic communities reduce CO2 to acetate. We assessed how preservation method and storage duration shape biocathode recovery. Cathodic biomass enriched for 44 days was preserved by freezing without cryoprotectant, freezing with glycerol, or lyophilization with a maltodextrin–trehalose stabilizer, stored for 39 or 174 days, and reactivated for 85–90 days. Storage duration, not preservation method, dominated recovery: current density and acetate production were threefold higher after 39 days than after 174 days, and coulombic efficiency fell from 75% to 43%. Short-term storage preserved an Acetobacterium-dominated community correlated with acetate production (R² = 0.8), whereas prolonged storage led to its near-loss and a more diverse but functionally diffuse assemblage, with Wood–Ljungdahl potential redistributed across Sporomusa-affiliated genomes alongside enriched sporulation functions. Storage duration therefore appears to act as a selective temporal filter favoring dormancy-competent lineages.