Utilisation of single added fatty acids by consortia of digester sludge in batch culture

Inocula derived from an anaerobic digester were used to study (i) their potential for methane production and (ii) the utilisation rates of different short chain fatty acids (SCFAs) by the microbial community in defined media with mono-carbon sources (formic-, acetetic-, propionic-, butyric acid) in batch culture. It could be demonstrated that the microbial reactor population could be transferred successfully to the lab, and its ability to build up methane was present even with deteriorating biogas plant performance. Therefore, this reduction in performance of the biogas plant was not due to a decrease in abundance, but due to an inactivity of the microbial community. Generally, the physico-chemical properties of the biogas plant seemed to favour hydrogenotrophic methanogens, as seen by the high metabolisation rates of formate compared with all other carbon sources. In contrast, acetoclastic methanogenesis could be shown to play a minor role in the methane production of the investigated biogas plant, although the origin of up to 66% of methane is generally suggested to be generated through acetoclastic pathway.