Microbial community shifts in the oxic-settling-anoxic process in response to changes to sludge interchange ratio

This particular study set out to demonstrate alterations on the microbial community of the oxic-settling-anaerobic/anoxic (OSA) process treating real domestic wastewater by changing interchange ratios (IRs). The sludge yield of systems operated at different IRs (1/13, 1/17 and 1/20) to assess sludge reduction was used to analyze microbial community composition variations. The highest IR (1/13) resulted in the highest sludge reduction (52.1%), while the OSA systems with IR of 1/17 and 1/20 reduced sludge production by 37.4% and 35.5%, respectively, in comparison to conventional systems. 16S rRNA gene amplicon sequencing analysis showed that the bacterial communities were composed of similar phylogenetic groups, Proteobacteria, Acidobacteria, and Bacteroidetes being dominant. The relative abundances differed due to the applied IRs. The highest abundance of Actinobacteria was determined at the highest IR (1/13) and increasing of the HRT to 1/20 caused a significant reduction in Actinobacteria species and the lowest abundance (6%) was determined in the OSA systems. The abundant of Thiothrix species that are boosted in the OSA trials may have a vital role in OSA systems, where its abundance was below the detection limits in the seed sludge sample. Therefore, they could be used as bioindicators in the OSA system

Fungal bioaugmentation of anaerobic digesters fed with lignocellulosic biomass: What to expect from anaerobic fungus Orpinomyces sp.

Energy-efficient biogas reactors are often designed and operated mimicking natural microbial ecosystems such as the digestive tracts of ruminants. Anaerobic fungi play a crucial role in the degradation of lignocellulose-rich fiber thanks to their high cellulolytic activity. Fungal bioaugmentation is therefore at the heart of our understanding of enhancing anaerobic digestion (AD). The efficiency of bioaugmentation with anaerobic fungus Orpinomyces sp. was evaluated in lignocellulose-based AD configurations. Fungal bioaugmentation increased the methane yield by 15-33% during anaerobic co-digestion of cow manure and selected cereal crops/straws. Harvesting stage of the crops was a decisive parameter to influence methane production together with fungal bioaugmentation. A more efficient fermentation process in the bioaugmented digesters was distinguished by relatively-higher abundance of Synergistetes, which was mainly represented by the genus Anaerobaculum. On the contrary, the composition of the methanogenic archaea did not change, and the majority of methanogens was assigned to Methanosarcina

Anaerobic co-digestion of cow manure and barley: Effect of cow manure to barley ratio on methane production and digestion stability

Anaerobic co-digestion of cow manure (CM) and barley (Hordeum vulgare, HV) was evaluated in terms of biochemical methane potentials with respect to five different CM to HV mixing ratios of 1:0, 2:1, 1:1, 1:2, and 0:1 based on volatile solids (VS) contents. Bacterial community composition of the seed sludge was examined using 454 pyrosequencing of 16S rRNA gene sequences. Based on the taxonomic classification, major bacterial phyla belonged to the Firmicutes (42%) and Bacteroidetes (22%). Co-digestion of CM and barley was superior at all mixing ratios when compared with the digestion of CM alone. The digestion systems failed at the ratio of 0:1, and there was no methane production. The presence of barley caused high acidification, but there was no volatile fatty acids accumulation at the end of the digestion. Highest specific methane productions were obtained at CM to HV mixing ratios of 2:1 and 1:1 as 216 CH4/g VS and 230 CH4/g VS, respectively. Because of the highest specific methane production, the optimal CM to HV mixing ratio was found to be 1:1 in this study. (c) 2015 American Institute of Chemical Engineers Environ Prog, 35: 589-595, 201

Enrichment of lignocellulose-degrading microbial communities from natural and engineered methanogenic environments

The aim of this study was to develop an effective bioaugmentation concept for anaerobic digesters treating lignocellulosic biomass such as straw. For that purpose, lignocellulose-degrading methanogenic communities were enriched on wheat straw from cow and goat rumen fluid as well as from a biogas reactor acclimated to lignocellulosic biomass (sorghum as mono-substrate). The bacterial communities of the enriched cultures and the different inocula were examined by 454 amplicon sequencing of 16S rRNA genes while the methanogenic archaeal communities were analyzed by terminal restriction fragment length polymorphism (T-RFLP) fingerprinting of the mcrA gene. Bacteroidetes was the most abundant phylum in all samples. Within the Bacteroidetes phylum, Bacteroidaceae was the most abundant family in the rumen-derived enrichment cultures, whereas Porphyromonadaceae was the predominant one in the reactor-derived culture. Additionally, the enrichment procedure increased the relative abundance of Ruminococcaceae (phylum: Firmicutes) in all cultures. T-RFLP profiles of the mcrA gene amplicons highlighted that the ruminal methanogenic communities were composed of hydrogenotrophic methanogens dominated by the order Methanobacteriales regardless of the host species. The methanogenic communities changed significantly during the enrichment procedure, but still the strict hydrogenotrophic Methanobacteriales and Methanomicrobiales were the predominant orders in the enrichment cultures. The bioaugmentation potential of the enriched methanogenic cultures will be evaluated in further studies

Biological pretreatment with Trametes versicolor to enhance methane production from lignocellulosic biomass: A metagenomic approach

The presence of poorly biodegradable components in lignocellulosic biomass limits the methane recovery in anaerobic digesters. The main reason to go for aerobic pretreatment before anaerobic digestion (AD) is to enable enzymatic cleavage of the aromatic rings in lignin by oxygen since it cannot be efficiently degraded under anaerobic conditions. In this study, the advantage of highly-cellulolytic white-rot fungi Trametes versicolor was taken by aerobic pretreatment prior to anaerobic co-digestion of cow manure and selected cereal crop materials (i.e. wheat, rye, barley, triticale) harvested at different stages. Fungal pretreatment improved the methane yield by 10%-18% and cellulose degradation up to 80%. Furthermore, higher volatile fatty acid (VFA) speciation was found in the anaerobic digesters upon fungal pretreatment. 16S rRNA gene amplicon sequencing revealed a more diverse microbial community in the fungal-pretreated anaerobic digesters. Generally, typically-detected bacterial species dominated the digesters; except that Synergistetes was only enriched in the fungal-pretreated digesters. Although Methanosarcianease was the predominant methanogenic archaea, a more diverse methanogenic population was identified in the fungal-pretreated digesters in which Methanobacteriaceaa and Methanomibrobiaceae also took role during biomethanation. Comparatively more unique microbiome of biogas reactors upon fungal pretreatment synergistically affected VFA production, cellulose degradation and eventually methane yield in an affirmative way. Considering the functional importance of bacterial and methanogenic archaeal populations, elevated knowledge of the microbial structures is essential for minimizing process failures and for creating strategies for process optimization of lignocellulose based-AD

Bioaugmentation of anaerobic digesters treating lignocellulosic feedstock by enriched microbial consortia

Three different bioaugmentation cultures enriched from natural and engineered cellulolytic environments (cow and goat rumen, a biogas reactor digesting sorghum biomass) were compared for their enhancement potential on the anaerobic digestion of wheat straw. Methane yields were determined in batch tests using the Automatic Methane Potential Test System operated for 30 days under mesophilic conditions. All cultures had positive effects on substrate degradation, and higher methane yields were observed in the bioaugmented reactors compared to control reactors set up with standard inoculum. However, the level of enhancement differed according to the type of the enrichment culture. Methane yield in batch reactors augmented with 2% cow rumen derived enrichment culture was increased by only 6%. In contrast, reactors amended with 2% goat rumen derived enrichment culture or with the bioaugmentation culture obtained from the biogas reactor digesting sorghum biomass produced 27 and 20% more methane, respectively. The highest methane yield was recorded in reactors amended with 6% goat rumen derived enrichment culture, which represented an increase by 36%. The microbial communities were quite similar at the end of the batch tests independently of the bioaugmentation sources, indicating that the introduced microbial communities of the enrichment cultures did not dominate the reactors

Rumen bacteria at work: bioaugmentation strategies to enhance biogas production from cow manure

AimsTo investigate the effects of different bioaugmentation strategies for enhancing the biogas production from cow manure and evaluate microbial community patterns

Use of PCR-DGGE based molecular methods to assessment of microbial diversity during anaerobic treatment of antibiotic combinations

As it is currently often not know how anaerobic bioreactors, e. g. for biogas production, react if the substrate is contaminated by toxic compounds like antibiotics. This study evaluated how anaerobic sequencing batch reactors were affected by amendments of different antibiotics and stepwise increasing concentrations. The compositions of microbial community were determined in the seed sludge using 16S rRNA gene clone libraries and PCR-DGGE analyses were used for the detection of microbial community changes upon antibiotics additions. According to PCR-DGGE results, the syntrophic interaction of acetogens and methanogens is critical to the performance of the reactors. Failure to maintain the stability of these microorganisms resulted in a decrease in the performance and stability of the anaerobic reactors. Assessment of DGGE data is also useful for suggesting the potential to control ultimate microbial community structure, especially derived from Gram-negative bacteria, through bioaugmentation to successful for antibiotic biodegradation. (C) 2015 Elsevier Ltd. All rights reserved

Effect of bioaugmentation by cellulolytic bacteria enriched from sheep rumen on methane production from wheat straw

The aim of this study was to determine the potential of bioaugmentation with cellulolytic rumen microbiota to enhance the anaerobic digestion of lignocellulosic feedstock. An anaerobic cellulolytic culture was enriched from sheep rumen fluid using wheat straw as substrate under mesophilic conditions. To investigate the effects of bioaugmentation on methane production from straw, the enrichment culture was added to batch reactors in proportions of 2% (Set-1) and 4% (Set-2) of the microbial cell number of the standard inoculum slurry. The methane production in the bioaugmented reactors was higher than in the control reactors. After 30 days of batch incubation, the average methane yield was 154 mL(N) CH4 g(-1)vs in the control reactors. Addition of 2% enrichment culture did not enhance methane production, whereas in Set -2 the methane yield was increased by 27%. The bacterial communities were examined by 454 amplicon sequencing of 16S rRNA genes, while terminal restriction fragment length polymorphism (T-RFLP) fingerprinting of mcrA genes was applied to analyze the methanogenic communities. The results highlighted that relative abundances of Ruminococcaceae and Lachnospiraceae increased during the enrichment. However, Cloacamonaceae, which were abundant in the standard inoculum, dominated the bacterial communities of all batch reactors. T-RFLP profiles revealed that Methanobacteriales were predominant in the rumen fluid, whereas the enrichment culture was dominated by Methanosarcinales. In the batch rectors, the most abundant methanogens were affiliated to Methanobacteriales and Methanomicrobiales. Our results suggest that bioaugmentation with sheep rumen enrichment cultures can enhance the performance of digesters treating lignocellulosic feedstock. (C) 2017 Elsevier Ltd. All rights reserved

Enhancing methane production from anaerobic co-digestion of cow manure and barley: Link between process parameters and microbial community dynamics

The effects of selected process parameters (i.e., temperature, inoculum to substrate ratio [I:S], and inoculum source) on methane production and microbial community structure were investigated in lignocellulose-based anaerobic digestion tests. The results highlighted that dynamic response of microbial communities in changing process parameters subsequently affected anaerobic digestion performance. Co-inoculation of cow rumen fluid to the seed sludge improved the methane yield by 18%. The overall highest methane yield (278 mL CH4/g volatile solids) was obtained when cow rumen fluid was co-inoculated with anaerobic seed sludge with an I:S ratio of 1:2 at mesophilic temperature. Based on 16S rRNA gene amplicon sequencing results, Clostridium, Bacteroides, and Bacillus were the predominant bacterial genera in all anaerobic digesters. The highest relative abundances of Clostridum and Bacillus were detected in the thermophilic anaerobic digester. The relative abundance of Rikenella; known for high cellulolytic activity, was significantly higher only in the cow rumen fluid-added digester. Comparatively higher abundances of these lignocellulose-degraders synergistically affected volatile fatty acids as well as methane production in these anaerobic digestion set ups. Methanobacterium was the most abundant methanogen in the digesters inoculated only with anaerobic seed sludge; whereas, Methanobrevibacter dominated the digester that was co-inoculated with cow rumen fluid