Bioaugmentation to improve anaerobic digestion of fish waste: Feed-to-microbes ratio, augmentation dosage and kinetic...

This study investigated bioaugmentation using fish waste (FW) adapted microbial consortia to overcome the limitations of inhibitory metabolites during anaerobic mono-digestion of FW. An enriched consortium developed through sequential batches improved COD removal from 62.4 % to 80.7 % and CH₄ yield from 369.7 to 434.9 mL/gVS_added. Protein-degrading bacteria (Fastidiosipila, Proteiniphilum, and Sedimentibacter) increased to 70.2 % of total abundance, while Methanosarcinaceae became dominant methanogens. Network analysis revealed strong syntrophic links between Fastidiosipila-Methanosaetaceae and Proteiniphilum-Methanosarcinaceae, driving efficient FW degradation. Bioaugmentation trials with varying feed-to-microbes (F/M) ratios (1-7) and dosages (0-40 %) showed that F/M 3 with 40 % dosage achieved the highest CH₄ yield (424.2 ± 2.1 mL/gVS_added, ∼30 % higher than the control). Two-way ANOVA indicated augmentation dosage primarily improved yield, while F/M ratio governed kinetics and stability. Overall, this study demonstrates bioaugmentation with pre-adapted consortia as a scalable approach to enhance mono-digestion of protein-rich FW for sustainable waste-to-energy conversion.