Bioaugmentation strategies based on bacterial and methanogenic cultures to relieve stress in anaerobic digestion of protein-rich substrates
Sara Agostini, Luca Bucci, Davide Doni, Paola Costantini, Ameya Pankaj Gupte, Bettina Müller, Fabrizio Sibilla, Marina Basaglia, Sergio Casella, Panagiotis Kougias, Stefano Campanaro, Lorenzo Favaro, Laura Treu
Abstract
Anaerobic co-digestion of protein-rich substrates is a prominent strategy for converting valuable feedstocks into methane, but it releases ammonia, which can inhibit the overall process. This study developed a cutting-edge combined culturomic and metagenomic approach to investigate the microbial composition of an ammonia-tolerant biogas plant. Newly-isolated microorganisms were used for bioaugmentation of stressed batch reactors fed with casein, maize silage and their combination. A co-culture enriched with proteolytic bacteria was isolated, selected and compared with the proteolytic collection strain Pseudomonas lundensis DSM6252. The co-culture and P. lundensis were combined with the ammonia-resistant archaeon Methanoculleus bourgensis MS2 to boost process stability. A microbial population pre-adapted to casein was also tested for evaluating the digestion of protein-rich feedstock. The promising results suggest combining proteolytic bacteria and M. bourgensis could exploit microbial co-cultures to improve anaerobic digestion stability and ensure stable productivity even under the harshest of ammonia conditions.