Inoculum selection is crucial to ensure operational stability in anaerobic digestion

Abstract

Anaerobic digestion is considered a key technology for the future bio-based economy. The microbial consortium carrying out the anaerobic digestion process is quite complex, and its exact role in terms of "elasticity", i.e., the ability to rapidly adapt to changing conditions, is still unknown. In this study, the role of the initial microbial community in terms of operational stability and stress tolerance was evaluated during a 175-day experiment. Five different inocula from stable industrial anaerobic digesters were fed a mixture of waste activated sludge and glycerol. Increasing ammonium pulses were applied to evaluate stability and stress tolerance. A different response in terms of start-up and ammonium tolerance was observed among the different inocula. Methanosaetaceae were the dominant acetoclastic methanogens, yet, Methanosarcinaceae increased in abundance at elevated ammonium concentrations. A shift from a Firmicutes to a Proteobacteria dominated bacterial community was observed in failing digesters. Methane production was strongly positively correlated with Methanosaetaceae, but also with Bacteria related to Anaerolinaceae, Clostridiales, and Alphaproteobacteria. Volatile fatty acids were strongly positively correlated with Betaproteobacteria and Bacteroidetes, yet ammonium concentration only with Bacteroidetes. Overall, these results indicate the importance of inoculum selection to ensure stable operation and stress tolerance in anaerobic digestion.

Microwave and ultrasound pre-treatments influence microbial community structure and digester performance in anaerobic digestion of waste activated sludge

“…Syntrophic activities generate substrates for methanogenesis, which have been hypothesised to be the explanation for observed correlations between high relative abundance of Clostridiales (or Clostridia) and improved methane production (Vanwonterghem et al 2014;Yue et al 2013). Decreased abundance of Firmicutes and increased abundance of the Proteobacteria phylum, together with a decline in methane production and increased ammonia, have furthermore been shown in mesophilic anaerobic degradation of WAS (De Vrieze et al 2015a). Correspondingly, we observed a strong and positive correlation between Clostridiales, Clostridia and Firmicutes relative abundance and richness and enhanced biogas generation, whereas the relative abundance of Alphaproteobacteria, Betaproteobacteria and Proteobacteria negatively correlated with increased substrate availability.…”

Treatment of Slaughterhouse Waste Water Mixed with Serum from Lacteal Industry of Extremadura in Spain to Produce Clean Energy

“…In general, industrial wastewater lacks suitable microorganisms to perform biodigestion, so it is necessary to have an acclimated inoculum [29]. In our case, as the starting inoculums in the biodigestor we use a mixture of anaerobic sludge from an urban sewage treatment plant and cow manure rich in methanogenic bacteria.…”

Hydrazone-modulated peptides for efficient gene transfection

“…The development and subsequent application of culture-independent molecular techniques, such as 16S rRNA gene amplicon sequencing, have led to a strong increase in knowledge concerning the microbial community in the AD process [10,11]. Microbial community evenness [12][13][14] and dynamics [8,15,16], whether or not influenced by a suitable inoculum [17], reflect the microbial community structure and organization, and can strongly impact AD process resilience. The identification of the main microbial groups, performing specific reactions, and their role in the AD process has paved the road for the development of microbial community-based process stability indicators [18][19][20][21][22][23].…”