Exploring an alternative source of DIETer to mitigate ammonia inhibition of swine manure by inoculum treating brewery wastewater

Bioaugmentation of ammonia inhibition was hindered by the availability of DIETer inoculum. The unacclimated ethanol-fed inoculum treating brewery wastewater was compared with ammonia acclimated inoculum to explore a way of alternative DIETer source. The overall performance, evolution of microbial community and metabolic functions were investigated. The unacclimated inoculum (194.71 +/- 1.98 mL CH4/VSadded) demonstrated feasible recovery in methane yield under ammonia stress (4000 mg/L) compared with acclimated inoculum (191.10 +/- 1.46 mL CH4/VSadded). The Methanothrix in the unacclimated group significantly (p < 0.05) decreased 31.60% than the acclimated group. Functional analysis indicated that the unacclimated Methanothrix-dominated inoculum had higher relative abundances in key enzymes of hydrogenotrophic methanogenesis. These statistical results revealed that the inoculum treating brewery wastewater serves as a firm foundation for the alternative DIETer inoculum source, broadening inoculums for mitigating ammonia stress. The threshold-type inhibition function also inspired a strategy to replace ethanol with ammonia (3000 similar to 8000 mg/L) for promoting DIETer, which could maintain direct interspecies electron transfer as the predominant working mode of interspecies electron exchange.

Automated summary

This study investigated the bioaugmentation of ammonia inhibition and explored alternative sources of DIETer inoculum for treating brewery wastewater. The results showed that the unacclimated inoculum demonstrated feasible recovery in methane yield under ammonia stress compared with the acclimated inoculum. Functional analysis revealed that the unacclimated inoculum had higher relative abundances in key enzymes of hydrogenotrophic methanogenesis. These findings suggest that the inoculum treating brewery wastewater serves as a firm foundation for alternative DIETer inoculum source, broadening inoculums for mitigating ammonia stress.