Efficacy of bioaugmentation with nondomesticated mixed microbial consortia under ammonia inhibition in anaerobic digestion

Bioaugmentation shows promise in mitigating ammonia-induced microbial inhibition in anaerobic digestion processes. However, the advanced technical requirements and high costs associated with pure strain cultivation, as well as the time-consuming and labor-intensive process of domesticating consortia, present challenges for industrial applications. Herein, the efficacy of bioaugmentation with nondomesticated mixed microbial consortia was evaluated, which resulted in a significant methane production improvement of 5.6%-11.7% and 10.3%- 13.5% under total ammonia nitrogen concentrations of 2.0 and 4.9 g-N/L, respectively. Microbial analysis revealed that at high ammonium levels, the bioaugmented culture facilitated a transition in the methanogenic pathway from acetoclastic to hydrogenotrophic by regulating symbiotic relationships between propionate- and acetate-oxidizing bacteria and methanogens. Consortium type and dose applied were identified as crucial factors determining bioaugmentation effectiveness. Overall, nondomesticated mixed microbial consortia demonstrate potential as cost-effective bioaugmentation agents for mitigating ammonia-induced inhibition.