Microbial community dynamics in replicate anaerobic digesters exposed sequentially to increasing organic loading rate, acidosis, and process recovery

Abstract

BackgroundVolatile fatty acid intoxication (acidosis), a common process failure recorded in anaerobic reactors, leads to drastic losses in methane production. Unfortunately, little is known about the microbial mechanisms underlining acidosis and the potential to recover the process. In this study, triplicate mesophilic anaerobic reactors of 100 L were exposed to acidosis resulting from an excessive feeding with sugar beet pulp and were compared to a steady-state reactor.ResultsStable operational conditions at the beginning of the experiment initially led to similar microbial populations in the four reactors, as revealed by 16S rRNA gene T-RFLP and high-throughput amplicon sequencing. Bacteroidetes and Firmicutes were the two dominant phyla, and although they were represented by a high number of operational taxonomic units, only a few were dominant. Once the environment became deterministic (selective pressure from an increased substrate feeding), microbial populations started to diverge between the overfed reactors. Interestingly, most of bacteria and archaea showed redundant functional adaptation to the changing environmental conditions. However, the dominant Bacteroidales were resistant to high volatile fatty acids content and low pH. The severe acidosis did not eradicate archaea and a clear shift in archaeal populations from acetotrophic to hydrogenotrophic methanogenesis occurred in the overfed reactors. After 11 days of severe acidosis (pH 5.2 ± 0.4), the process was quickly recovered (restoration of the biogas production with methane content above 50 %) in the overfed reactors, by adjusting the pH to around 7 using NaOH and NaHCO3.ConclusionsIn this study we show that once the replicate reactors are confronted with sub-optimal conditions, their microbial populations start to evolve differentially. Furthermore the alterations of commonly used microbial parameters to monitor the process, such as richness, evenness and diversity indices were unsuccessful to predict the process failure. At the same time, we tentatively propose the replacement of the dominant Methanosaeta sp. in this case by Methanoculleus sp., to be a potential warning indicator of acidosis.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0309-9) contains supplementary material, which is available to authorized users.

Bio-Hydrogen Production From Buffalo Waste With Rumen Inoculum and Metagenomic Characterization of Bacterial and Archaeal Community

“…The first three main phyla are reported as part of a core group by numerous authors (Abendroth et al, 2015;Bassani et al, 2015;Duda et al, 2015;Goux et al, 2015). In AD of cattle manure and sludge, some authors (Rivière et al, 2009;St-Pierre and Wright, 2014;Campanaro et al, 2016) reported, as part of the core group, also Cloroflexi, which, on the contrary, we found at 0.03% only.…”

Effect of Seasonal Temperature on the Performance and on the Microbial Community of a Novel AWFR for Decentralized Domestic Wastewater Pretreatment

“…During the start-up period, the dominant class was Gammaproteobacteria affiliated with the phylum Proteobacteria, with a relative abundance of 13.67%, followed by Bacteroidia, Clostridia, Anaerolineae and Bacilli, with a relative abundance of 12.87%, 11.88%, 10.96% and 9.89%, respectively. Among these predominant classes, Bacteroidia and Clostridia played significant roles in hydrolysis metabolism [47][48][49]. Gammaproteobacteria was the most representative class during the start-up period, which was also the main contributor to the phylum Proteobacteria.…”

“…These results probably indicate that seasonal temperature in summer benefited the growth of Bacilli bacteria. Bacteroidales affiliated with the class Bacteroidia had been identified as hydrolyser and fermenter that participated in the conversation of cellulose and polysaccharide into VFAs [49]. Clostridiales affiliated with the class Clostridia was correlated with methane production, due to their diverse metabolism that utilized polysaccharide fermentation to produce VFAs for methanogenesis [47,48].…”

Characteristics of Pollutants and Microbial Communities Obtained in Simulated Lysimeters of Swine Carcasses

“…The relative abundances of Methanoculleus and Methanosprillum in Lysimeters 1 and 2 were higher than that in Lysimeter 3. Previous studies reported that the predominance of hydrogenotrophic methanogens such as Methanoculleus and Methanosprillum was found under stress conditions, and that it might be related to its tolerance of high ammonia concentrations [38,40,41].…”

“…Clostridia were the most predominant class in Lysimeters 2 and 3 with an abundance of 23.1% and 25.3%, respectively. Bacteroidetes was mainly founded in anaerobic digestion and resistant to adverse environmental conditions such as low pH and temperature [17,38].…”