3 years ago

Thermophilic alkaline fermentation followed by mesophilic anaerobic digestion for efficient hydrogen and methane production from waste activated sludge: Focusing on dynamics of bacterial pathogens as revealed by the combination of metagenomic and qPCR analysis.

Yuhang Jing, Gang Luo, Yue Rao, Shicheng Zhang, Jingjing Wan
Thermophilic alkaline fermentation followed by mesophilic anaerobic digestion (TM) for hydrogen and methane production from waste activated sludge (WAS) was investigated. TM process was also compared to mesophilic alkaline fermentation followed by mesophilic anaerobic digestion (MM) process and one-stage mesophilic anaerobic digestion (M) process. The results showed that both hydrogen yield (74.5 mLH2/gVS) and methane yield (150.7 mLCH4/gVS) in TM process were higher than those (6.7 mLH2/gVS and 127.8 mLCH4/gVS) in MM process. The lowest methane yield (101.2 mLCH4/gVS) was obtained in M process. Taxonomic results obtained from metagenomic analysis showed that different microbial community compositions were established in the hydrogen reactors of TM and MM processes, which also significantly changed the microbial community compositions in the following methane reactors compared to M process. The dynamics of bacterial pathogens were also evaluated. For TM process, the reduction of diversity and total abundance of bacterial pathogens in WAS were observed in hydrogen rector, which was further reduced in methane reactor as revealed by metagenomic analysis. The results also showed not all the bacterial pathogens were reduced in the reactors. E.g Collinsella aerofaciens was enriched in the hydrogen reactor, which was also confirmed by qPCR analysis. The study further showed qPCR was more sensitive to detect bacterial pathogens compared to metagenomic analysis. Although there were some differences in the relative abundances of bacterial pathogens calculated by metagenomic and qPRC approaches, both approaches demonstrated TM process was efficient for the removal of bacterial pathogens compared to MM and M processes.IMPORTANCE: The study developed an efficient process for bioenergy (H2 and CH4) production from WAS, and also elucidate the dynamics of bacterial pathogens in the process, which is important for the utilization and safe application of WAS. The study also made an attempt to combine metagenomic and qPCR analysis to reveal the dynamics of bacterial pathogens in anaerobic processes, which could overcome the limitations of each method and provide new insights of bacterial pathogens in environmental samples.

Publisher URL: http://doi.org/10.1128/AEM.02632-17

DOI: 10.1128/AEM.02632-17

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