Lyophilizaition, recovery and bioaugmentation of methaogens
In this study, an ammonia tolerant methanogenic consortium was lyophilized and used, after 180 days of storage, as bioaugmentation inoculum to alleviate severe ammonia toxicity (5.0 g NH4+-N L-1). The results demonstrated that, under thermophilic conditions, the addition of the lyophilized inoculum yielded an immediate increase in methane production by 42.65%, compared to the ammonia-control reactor. Additionally, bioaugmentation recovered 86.46% of the uninhibited methane production achieved by a control reactor at 0.45 g NH4+-N L-1. Microbiological analyses showed that Methanothermobacter sp. and M. bourgensis, included in the lyophilized bioaugmentation inoculum, became the dominant methanogenic species in the reactor after bioaugmentation, thereby confirming the success of bioaugmentation using long-term stored and ready-to-use inoculum with a high revival rate. Overall, this study demonstrated for the first time that lyophilized methanogenic consortia can be successfully used after a long-term storage under ambient conditions, to alleviate ammonia toxicity in biomethanation of problematic biomasses.