Communities In Anaerobic Digesters Research Articles

Effect of hydrothermal-acid pretreatment on methane yield and microbial community in anaerobic digestion of rice straw

Hydrothermal pretreatment has been proposed to enhance straw methane yield during anaerobic digestion recently. However, the combined effect of hydrothermal and organic acid pretreatment (HTOAP) needs further investigation. This study identified optimal pretreatment at 120 °C with 3 % acetic acid for 24 h by orthogonal design method. The HTOAP increased the reducing sugar content by destroying the lignocellulosic structure. A 79 % increment of methane production after HTOAP was observed compared to the untreated group. Microbial analysis showed that HTOAP enriched the relative abundance of lignocellulose-degraders, such as W5053, Thermanaerovibrio, Caldicoprobacter, as well as the syntrophic acetate oxidizing bacteria Syntrophaceticus. Moreover, Methanobacterium conducted hydrogenotrophic methanogenesis dominantly. Furthermore, the potential function analysis showed that HTOAP stimulated the expression of key enzymes in the hydrogenotrophic pathway, including carbon-monoxide dehydrogenase (EC 1.2.7.4) and coenzyme F420 hydrogenase (EC 1.12.98.1). This investigation illustrated the potential of HTOAP of rice straw to facilitate methane production.

Levels of microbial diversity affect the stability and function of dark fermentation bioreactors

Climate change and pollution drive the need for fossil fuel alternatives. Dark fermentation offers promise through the use of microbial consortia to convert organic matter into hydrogen gas. Persisting challenges like instability and low yields may stem from reduced diversity of the anaerobic digestion communities that serve as inoculum and undergo aggressive pretreatments and culturing conditions. This study explores the impact of diversity loss on function, focusing on biogas production and stability. Two treatments, with and without aggressive pretreatment, were tested on 12 replicate bioreactors each, resulting in differing microbial diversity levels. Microbial communities were assessed via 16S amplicon sequencing, monitoring biogas production, volatile fatty acids, and testing invasion susceptibility. The two treatments exhibited divergent assembly and functional trajectories, although replicates within each treatment ultimately converged into similar compositions and stable levels of biogas production. Heat-treated bioreactors showed a 91.5% biogas increase but exhibited higher invasion susceptibility compared to non-treated. Non-treated bioreactors showed unique species associations with biogas production (e.g. Ethanoligenens harbinense and Enterococcus olivae), distinct from the commonly studied Clostridium group. These findings provide insights into the effects of diversity loss on stability, elucidating differences across taxonomic and functional stability as well as invasion susceptibility. Moreover, the identification of novel bacterial groups associated with hydrogen production suggests promising directions for future research to enhance microbial consortia control and design in dark fermentation.

Integration of hydrothermal liquefied sludge as wastewater for anaerobic treatment and energy recovery: Aqueous phase characterization, anaerobic digestion performance and energy balance analysis

For the hydrothermal liquefaction (HTL) process as the final method for waste activated sludge, the liquid by-product of the process, i.e., the HTL aqueous solution, poses the greatest bottleneck due to its large volume and contaminant levels. In this study, the effects of hydrothermal liquefaction pretreatment (HTL) on the performance of anaerobic digestion and energy balance of the waste-activated sludge (WAS) aqueous phase were investigated. The results showed that HTL could greatly increase the hydrolysis of WAS and enhance the protein, polysaccharide and volatile fatty acid contents in the aqueous phase. The anaerobic digestion showed that the optimal gas and methane production efficiency was achieved at 160 °C. Positive net energy gain was obtained in each process (ΔE) and the optimal HTL heat recovery rate was obtained at 160 °C. HTL was found to improve the hydrolyzing bacterial community in anaerobic digestion but had little effect on the archaeal community.

Temperature drives microbial communities in anaerobic digestion during biogas production from food waste.

Resource depletion and climate changes due to human activities and excessive burning of fossil fuels are the driving forces to explore alternatives clean energy resources. The objective of this study was to investigate the potential of potato peel waste (PPW) at various temperatures T15 (15°C), T25 (25°C), and T35 (35°C) in anaerobic digestion (AD) for biogas generation. The highest biogas and CH4 production (117mL VS-g and 74mL VS-g) was observed by applying 35°C (T35) as compared with T25 (65mL VS-g and 22mL VS-g) on day 6. Changes in microbial diversity associated with different temperatures were also explored. The Shannon index of bacterial community was not significantly affected, while there was a positive correlation of archaeal community with the applied temperatures. The bacterial phyla Firmicutes were strongly affected by T35 (39%), whereas Lactobacillus was the dominant genera at T15 (27%). Methanobacterium and Methanosarcina, as archaeal genera, dominated in T35 temperature reactors. In brief, at T35, Proteiniphilum and Methanosarcina were positively correlated with volatile fatty acids (VFAs) concentration. Spearman correlation revealed dynamic interspecies interactions among bacterial and archaeal genera; facilitating the AD system. This study revealed that temperature variations can enhance the microbial community of the AD system, leading to increased biogas production. It is recommended for optimizing the AD of food wastes.

Decoding Microbial Responses to Ammonia Shock Loads in Biogas Reactors through Metagenomics and Metatranscriptomics.

The presence of elevated ammonia levels is widely recognized as a significant contributor to process inhibition in biogas production, posing a common challenge for biogas plant operators. The present study employed a combination of biochemical, genome-centric metagenomic and metatranscriptomic data to investigate the response of the biogas microbiome to two shock loads induced by single pulses of elevated ammonia concentrations (i.e., 1.5 g NH4+/LR and 5 g NH4+/LR). The analysis revealed a microbial community of high complexity consisting of 364 Metagenome Assembled Genomes (MAGs). The hydrogenotrophic pathway was the primary route for methane production during the entire experiment, confirming its efficiency even at high ammonia concentrations. Additionally, metatranscriptomic analysis uncovered a metabolic shift in the methanogens Methanothrix sp. MA6 and Methanosarcina flavescens MX5, which switched their metabolism from the acetoclastic to the CO2 reduction route during the second shock. Furthermore, multiple genes associated with mechanisms for maintaining osmotic balance in the cell were upregulated, emphasizing the critical role of osmoprotection in the rapid response to the presence of ammonia. Finally, this study offers insights into the transcriptional response of an anaerobic digestion community, specifically focusing on the mechanisms involved in recovering from ammonia-induced stress.

Establishment of an Electroactive Microorganism Community in Anaerobic Digestion with Photosynthetic Bacteria Agents for Promoting Methane Production

Establishment of an Electroactive Microorganism Community in Anaerobic Digestion with Photosynthetic Bacteria Agents for Promoting Methane Production

Cold isostatic pressing-study on methane production and microbial communities in anaerobic digestion of wheat straw with high-solids

In this study, the effect of cold isostatic pressing (CIP) pretreatment on the physicochemical properties and subsequent anaerobic digestion (AD) performance of wheat straw (WS) was explored, which did not have additional chemical reagent over the whole process. The WS was subjected to CIP pretreatment by pressures from 350 to 700 MPa, respectively, while AD was carried out at mesophilic temperature with total solids (TS) 7% and 14%. The mapping indicated that the CIP pretreatment promoted the hydrolysis of WS by destroying the dense structure. The CIP pretreatment changed pH and volatile fatty acids (VFAs) in the AD system. Compared with the control group, the cumulative methane production of CIP pretreatment group with TS 14% increased by 22.07%–56.18%. The acetic acid concentration peaked on 4th day and 14th day with 3943.23 mg/L and 3815.21 mg/L, respectively, in H600, and propionic acid concentration also reached two peaks at the same time with 2014.92 mg/L and 2405.20 mg/L, respectively. It was also observed that the CIP pretreatment maintained the pH in the range of 6.44–7.40, maintaining the stability of the overall system. It was also found that CIP pretreatment increased 9 species of hydrolysis and acidogenic bacteria, and methanogen Methanosarcina, thereby facilitating the hydrolysis and methanogenic stages. Predictive functional profiling comfirmed that CIP pretreatment could promote glycolysis/gluconeogenesis, fatty acid metabolism, and fatty acid degradation, whose relative abundance increased from 1.10% to 1.13%, 0.60%–0.62%, and 0.19%–0.23%. Methanogenic capacity of the system was improved because of CIP pretreatment enhancing the accessibility of microorganisms by disrupting the microstructure of WS. The energy conversion analysis showed that this method without chemical reagent addition is feasible for high-solids anaerobic digestion.

Functional and molecular approaches for studying and controlling microbial communities in anaerobic digestion of organic waste: a review

Functional and molecular approaches for studying and controlling microbial communities in anaerobic digestion of organic waste: a review

Propidium monoazide - polymerase chain reaction reveals viable microbial community shifts in anaerobic membrane bioreactors treating domestic sewage at low temperature

An anaerobic membrane bioreactor (AnMBR) treated domestic sewage at 15 °C under different hydraulic retention time (HRT) conditions (6, 12, 16, and 24 h). Propidium monoazide (PMA)-PCR excluded microorganisms without intact cell membranes, focusing on the viable microbial community in anaerobic digestion. The results showed that the 6-hour HRT had poor treatment performance: low chemical oxygen demand removal efficiency (below 80%) and high mean trans-membrane pressure and flux (15 kPa and 9.4 L/(m2 h)). Comparatively, PMA-PCR combined with next-generation sequencing improved the identification of microbial changes compared to conventional 16S rRNA gene sequencing. HRT influenced microorganisms in the hydrolysis and acid-production stages, including carbohydrate-degrading bacteria such as Bifidobacterium and Prevotella 1. Remarkably, a comparison with an AnMBR at 25 °C showed Proteobacteria to be the main cause of membrane fouling in the low-temperature AnMBR, with most operational taxonomic units negatively correlated with HRT and solids retention time.

Metaproteomic Analysis of the Anaerobic Community Involved in the Co-Digestion of Residues from Sugarcane Ethanol Production for Biogas Generation

The proteomics analysis could contribute to better understand about metabolic pathways in anaerobic digestion community because it still as a “black-box” process. This study aimed to analyze the proteins of the anaerobic co-digestion performed in reactors containing residues from the first and second generation ethanol production. Metaproteomics analysis was carried out for three types of samples: anaerobic sludge without substrate (SI), semi-continuous stirred reactor (s-CSTR) with co-digestion of filter cake, vinasse, and deacetylation liquor (R-CoAD) and s-CSTR with co-digestion of these aforementioned residues adding Fe3O4 nanoparticles (R-NP). The R-CoAD reactor achieved 234 NmLCH4 gVS−1 and 65% of CH4 in the biogas, while the R-NP reactor reached 2800 NmLCH4 gVS−1 and 80% of CH4. The main proteins found were enolase, xylose isomerase, pyruvate phosphate dikinase, with different proportion in each sample, indicating some change in pathways. However, according to those identified proteins, the main metabolic routes involved in the co-digestion was the syntrophic acetate oxidation coupled with hydrogenotrophic methanogenesis, with the CH4 production occurring preferentially via CO2 reduction. These findings contributed to unravel the anaerobic co-digestion at a micromolecular level, and may select a more appropriate inoculum for biogas production according to that residue, reducing reaction time and increasing productivity.

Influence of organic load on biogas production and response of microbial community in anaerobic digestion of food waste

Organic load (OL) is one important parameter influencing performance of anaerobic digestion, yet it is unclear how it affects the biogas composition and microbial community. This work investigated the influence of OL on biogas production from food waste (FW) and the response of microbial community. Results showed that the main biogas component was methane at low OLs (<10 g VS/L) while it turned into hydrogen at high OLs (>10 g VS/L). The optimum methane and hydrogen yields were 184.4 and 61.3 mL/g VS, corresponding to the OLs of 4 and 20 g VS/L, respectively. Analysis of microbial community indicated that high OLs leaded to the decrease of hydrolysis bacteria and methanogen while it helped to increase the relative abundance of hydrogen-producing bacteria. This study cast an insight that it is essential to control the OL and reinforce the hydrogenogen to obtain high output of hydrogen energy.

Physicochemical Parameters and Microbial Community in Anaerobic Digestion of Organic Wastes

The demand for an alternative source of energy and challenge of increase in wastes pollution initiates the need for renewable energy and management of waste using anaerobic digestion (AD). Anaerobic digestion is an effective and efficient method of waste treatment and energy generation. The study focused on investigating the physicochemical parameters and microbial community in anaerobic digestion of organic wastes and was conducted using chicken wastes and food wastes as organic substrate under semi-continuous conditions at hydraulic retention time (HRT) of forty-two (42) days in fifteen liter (15L) fabricated digesters labeled D1, D2 and D3 at 37OC. The pH, volatile fatty acid (VFA), moisture content (MC), total ammonia, total solid, volatile solid, alkalinity was assessed before and after digestion while the microbial community diversity was analyzed using 16S rRNA amplicon-based nextgeneration sequencing (NGS). The results indicated a pH value of 6.65 ± 0.12, 7.27 ± 0.13, 6.43 ± 0.27, volatile fatty acid of 72.17 ± 1.42, 58.35 ± 2.58, 40.56 ± 0.38 and moisture content of 98.9 ± 2.65, 92.3 ± 1.81, 96.4 ± 3.60 at day 42 for D1 (Chicken waste and food wastes), D2 (Chicken wastes+), D3 (control) respectively. A collective biogas yield of 686±17.00 kpa for D1, 700±11.00kpa for D2 and 521±21.00 kpa for D3 were recorded. The characterization of biogas analyzed with nondispersive infrared (NDIR) gas analyzer (gas board 3100p) revealed a percentage methane content of 46.11±1.11, 52.4±1.05, 50.31±1.33 for D1, D2 and D3 respectively. The microbial community identified phylum Bacteroidetes, Firmicutes, proteobacteria, Tenericutes, Verrucomicrobia, Actinobacteria, Euryarchaeota among others. The study shows that physicochemical properties and microbial community diversity are useful tools to indicate digester performance and also to enhance anaerobic digestion process.

Deeper Insights into the Effects of Microwave Hydrothermal Pretreatment on Methane Production and Microbial Community in Anaerobic Digestion

Deeper Insights into the Effects of Microwave Hydrothermal Pretreatment on Methane Production and Microbial Community in Anaerobic Digestion

Monitoring of seven industrial anaerobic digesters supplied with biochar

BackgroundRecent research articles indicate that direct interspecies electron transfer (DIET) is an alternative metabolic route for methanogenic archaea that improves microbial methane productivity. It has been shown that multiple conductive materials such as biochar can be supplemented to anaerobic digesters to increase the rate of DIET. However, the industrial applicability, as well as the impact of such supplements on taxonomic profiles, has not been sufficiently assessed to date.ResultsSeven industrial biogas plants were upgraded with a shock charge of 1.8 kg biochar per ton of reactor content and then 1.8 kg per ton were added to the substrate for one year. A joint analysis for all seven systems showed a decreasing trend for the concentration of acetic acid (p < 0.0001), propionic acid (p < 0.0001) and butyric acid (p = 0.0022), which was significant in all cases. Quantification of the cofactor F420 using fluorescence microscopy showed a reduction in methanogenic archaea by up to a power of ten. Methanogenic archaea could grow within the biochar, even if the number of cells was 4 times less than in the surrounding sludge. 16S-rRNA gene amplicon sequencing showed a higher microbial diversity in the biochar particles than in the sludge, as well as an accumulation of secondary fermenters and halotolerant bacteria. Taxonomic profiles indicate microbial electroactivity, and show the frequent occurrence of Methanoculleus, which has not been described in this context before.ConclusionsOur results shed light on the interplay between biochar particles and microbial communities in anaerobic digesters. Both the microbial diversity and the absolute frequency of the microorganisms involved were significantly changed between sludge samples and biochar particles. This is particularly important against the background of microbial process monitoring. In addition, it could be shown that biochar is suitable for reducing the content of inhibitory, volatile acids on an industrial scale.

Profiling temporal dynamics of acetogenic communities in anaerobic digesters using next-generation sequencing and T-RFLP

Acetogens play a key role in anaerobic degradation of organic material and in maintaining biogas process efficiency. Profiling this community and its temporal changes can help evaluate process stability and function, especially under disturbance/stress conditions, and avoid complete process failure. The formyltetrahydrofolate synthetase (FTHFS) gene can be used as a marker for acetogenic community profiling in diverse environments. In this study, we developed a new high-throughput FTHFS gene sequencing method for acetogenic community profiling and compared it with conventional terminal restriction fragment length polymorphism of the FTHFS gene, 16S rRNA gene-based profiling of the whole bacterial community, and indirect analysis via 16S rRNA profiling of the FTHFS gene-harbouring community. Analyses and method comparisons were made using samples from two laboratory-scale biogas processes, one operated under stable control and one exposed to controlled overloading disturbance. Comparative analysis revealed satisfactory detection of the bacterial community and its changes for all methods, but with some differences in resolution and taxonomic identification. FTHFS gene sequencing was found to be the most suitable and reliable method to study acetogenic communities. These results pave the way for community profiling in various biogas processes and in other environments where the dynamics of acetogenic bacteria have not been well studied.

Effects of Temperature and Stirring on the Changes of Antibiotic Resistance Genes and Microbial Communities in Anaerobic Digestion of Dairy Manure

To investigate the effects of temperature and stirring on antibiotic resistance genes (ARGs) and microbial communities during the anaerobic digestion of dairy manure, mesophilic and thermophilic anaerobic digestion experiments were performed with and without stirring. Two-way analysis of variance indicated that temperature affected biogas production more strongly than stirring (η2=0.934>0.911), and thermophilic and stirring increased the total biogas yield by 13.93% and 12.63%, respectively. The effect of temperature on the removal of ARGs was also stronger than that of stirring (η2=0.992>0.920), where thermophilic conditions enhanced the reduction of ARGs and MGEs to 0.09-1.53 (logarithm), while stirring had no significant effects. When temperature was altered from mesophilic to thermophilic, the microbial communities shifted, with Firmicutes becoming the dominant phylum after thermophilic anaerobic digestion, with a relative abundance of >86%. Network analysis demonstrated that eight genera including Sedimentibacter, Sphaerochaeta, and Pseudomonas were the hosts of ARGs and MGEs, and the redundancy analysis suggested that physicochemical parameters play important roles in shaping microbial communities, especially TAN and TVFAs, which indirectly affected the ARGs by altering their host bacteria.

Effects of different pretreatment methods on biogas production and microbial community in anaerobic digestion of wheat straw.

The pretreatment of wheat straw has been recognized to be an essential step prior to anaerobic digestion, owing to the high abundance of lignocellulosic materials. In order to choose economical and effective techniques for the disposal of wheat straw, effects of five pretreatment methods including acid, alkali, co-pretreatment of acid and alkali, CaO2, and liquid digestate of municipal sewage sludge on anaerobic digestion of wheat straw were investigated by analyzing biogas production and organic matter degradation in the study. The results showed that among these pretreatment methods, the methane yield was highest in the liquid digestate pretreated-wheat straw with 112.6mL gTS-1, followed by the acid, alkali, and CaO2 pretreatments, and the lowest was observed in the co-pretreatment of acid and alkali. Illumina MiSeq sequencing of the microbial communities in the anaerobic digesters revealed that the genera Ruminiclostridium including Ruminiclostridium and Ruminiclostridium 1, Hydrogenispora, and Capriciproducens were the main hydrolytic bacteria, acidogenic bacteria, and acetogenic bacteria, respectively, in the anaerobic digesters. Capriciproducens and Hydrogenispora dominated in the first and the later stages, respectively, in the anaerobic digesters, which could work as indicators of the anaerobic co-digestion stage of sludge and wheat straw. The total solid and SO42--S contents of the solid digestate and the NH4+-N concentration of the liquid digestate had a significant influence on the microbial community in the digesters. These findings indicated that liquid digestate pretreatment was a potential option to improve the anaerobic digestion of wheat straw, due to the low cost without additional chemical agents.

Illumina sequencing of 16S rRNA genes reveals a unique microbial community in three anaerobic sludge digesters of Dubai.

Understanding the microbial communities in anaerobic digesters, especially bacteria and archaea, is key to its better operation and regulation. Microbial communities in the anaerobic digesters of the Gulf region where climatic conditions and other factors may impact the incoming feed are not documented. Therefore, Archaeal and Bacterial communities of three full-scale anaerobic digesters, namely AD1, AD3, and AD5 of the Jebel Ali Sewage water Treatment Plant (JASTP) were analyzed by Illumina sequencing of 16S rRNA genes. Among bacteria, the most abundant genus was fermentative bacteria Acetobacteroides (Blvii28). Other predominant bacterial genera in the digesters included thermophilic bacteria (Fervidobacterium and Coprothermobacter) and halophilic bacteria like Haloterrigena and Sediminibacter. This can be correlated with the climatic condition in Dubai, where the bacteria in the incoming feed may be thermophilic or halophilic as much of the water used in the country is desalinated seawater. The predominant Archaea include mainly the members of the phyla Euryarchaeota and Crenarchaeota belonging to the genus Methanocorpusculum, Metallosphaera, Methanocella, and Methanococcus. The highest population of Methanocorpusculum (more than 50% of total Archaea), and other hydrogenotrophic archaea, is in agreement with the high population of bacterial genera Acetobacteroides (Blvii28) and Fervidobacterium, capable of fermenting organic substrates into acetate and H2. Coprothermobacter, which is known to improve protein degradation by establishing syntrophy with hydrogenotrophic archaea, is also one of the digesters' dominant genera. The results suggest that the microbial community in three full-scale anaerobic digesters is different. To best of our knowledge this is the first detailed report from the UAE.

Effects of polyethylene microplastics on the fate of antibiotic resistance genes and microbial communities in anaerobic digestion of dairy wastes

Microplastics (MPs) have been confirmed to affect the digestion performance of the anaerobic digestion (AD) and to influence the occurrence of antibiotic resistance genes (ARGs) in the environment. In this study, the effects of polyethylene (PE) MPs on digestion performance and the fate of ARGs and microbial communities in thermophilic AD (55 °C) and hyperthermophilic AD (65 °C) of dairy wastes were investigated. The results showed that the effects of PE MPs were similar at different temperatures. At 55 °C and 65 °C, the presence of PE MPs improved methane production by 8.4% and 41.2% and enhanced COD removal rates to 52.8% and 52.4%, respectively, mainly by increasing the abundances of microorganisms involved in hydrolysis, acidogenesis and acid utilization (e.g. Clostridium , Dechloromonas and Caldicoprobacter ). PE MPs significantly increased the fold changes in the abundances of tet C, tet G and tet W from 0.71 to 12.63 to 1.15–28.62. According to redundancy analysis and correlation analysis, free ammonia contributed the most (51% of the total variation) to the changes in host bacteria, which probably changed the fate of ARGs in different AD system. This study indicated the discharge of PE MPs presents a novel challenge in reducing the risks of ARG transmission. • The effects of polyethylene microplastics on anaerobic digestion were investigated. • Polyethylene efficiently increased the methane production and COD removal rate. • Polyethylene significantly increased the abundances of tet C, tet G and tet W. • Polyethylene shifted the microbial communities involving gas production.

Comparison of the microbial communities in anaerobic digesters treating high alkalinity synthetic wastewater at atmospheric and high-pressure (11 bar)

High-pressure anaerobic digestion is an appealing concept since it can upgrade biogas directly within the reactor. However, the decline of pH caused by the dissolution of CO2 is the main barrier that prevents a good operating high-pressure anaerobic digestion process. Therefore, in this study, a high-pressure anaerobic digestion was studied to treat high alkalinity synthetic wastewater, which could not be treated in a normal-pressure anaerobic digester. In the high-pressure reactor, the pH value was 7.5 ~ 7.8, and the CH4 content reached 88% at 11 bar. Unlike its normal-pressure counterpart (2285 mg/L acetic acid), the high-pressure reactor ran steadily (without volatile fatty acids inhibition). Furthermore, the microbial community changed in the high-pressure reactor. Specifically, key microbial guilds (Syntrophus (11.2%), Methanosaeta concilii (50.9%), and Methanobrevibacter (26.8%)) were dominant in the high-pressure reactor at 11 bar, indicating their fundamental roles under high-pressure treating high alkalinity synthetic wastewater.