Microbial community dynamics at high organic loading rates revealed by pyrosequencing during sugar refinery wastewater treatment in a UASB reactor

Diversity and Abundance of Microbial Communities in UASB Reactors during Methane Production from Hydrolyzed Wheat Straw and Lucerne

“…However, less knowledge about microbial communities in UASB reactors is available and studies related to operation with high strength substrates, as in the present study, are scarce [35,36,40]. In addition, only few previous studies have investigated the effects of increasing loads using high COD substrates [36,40]. These previous studies show good possibilities to treat such substrates in UASB systems but also risk VFA accumulation, acidification, and reduced methane production efficiency.…”

“…Many studies have investigated the microbial community composition in CSTR processes with the aim to understand its response to various operating parameters and performance variables (as reviewed in [19]). However, less knowledge about microbial communities in UASB reactors is available and studies related to operation with high strength substrates, as in the present study, are scarce [35,36,40]. In addition, only few previous studies have investigated the effects of increasing loads using high COD substrates [36,40].…”

“…These previous studies show good possibilities to treat such substrates in UASB systems but also risk VFA accumulation, acidification, and reduced methane production efficiency. Microbial communities in these previously studied processes, operating with hydrolyzed brewer's spent grain or sugar refinery wastewater, illustrated good capability in response to the increasing loads, with changes in both composition and distribution of both fermentative acidogenic bacteria, particularly members within phylum Bacteroidetes, and methanogens [36,40].…”

“…However, it might also lead to a higher concentration of acetic acid in the reactor which, if the alkalinity is not sufficient, can lead to a decrease in the pH and an increase in the undissociated form of acetic acid and other VFAs. The undissociated forms of several VFAs, including acetic, propionic, and butyric acids, have been shown to be inhibitory to a wide variety of bacteria and methanogens, to varying degrees, while the dissociated forms are generally considerably less inhibitory [29][30][31][32][33][34][35][36][37]. Operating strategies leading to reduced risks of acid accumulation and pH drop are thus desirable.…”

Impact of process temperature and organic loading rate on cellulolytic / hydrolytic biofilm microbiomes during biomethanation of ryegrass silage revealed by genome-centered metagenomics and metatranscriptomics

“…Apart from fermentative bacteria, the order Thermoanaerobacteriales, including several known syntrophic acetate-oxidizing bacteria e.g., Caldanaerobacter and Alkaliphilius, was shown to increase [32]. The methanogenic archaeal community mainly consisted of members of the genera Methanosarcina [33][34][35]. The Methanobacteria, Methanomicrobiales, and/or Methanomassiliicoccaceae members were also observed in certain AD-processes featuring a high organic load, depending on other prevailing conditions [36].…”