Anaerobic Biodegradation Research Articles

Factors affecting distribution and ecological risk assessment of volatile organic compounds (VOCs) in groundwater of the Huazhou district in northwestern China

Volatile organic compounds (VOCs) pollution in groundwater is a significant global concern. In this study, 26 groundwater samples were collected from the unconfined aquifers in Huazhou District, northwestern China, to assess their distribution characteristics, influencing factors, and ecological risks across various geomorphological settings. The findings revealed 35 VOCs in collected groundwater samples, with aromatic hydrocarbons having the highest detection rate (100%), and the VOCs distribution exhibited significant spatial variations, with the highest VOCs concentration near a chemical plant on the inclined pluvial plain. The lithology and groundwater flow influenced the vertical and lateral transport of VOCs, with concentrations decreasing as the aquifer permeability decreases along the groundwater flow from the inclined pluvial plain to the river. The Mantel test was used to analyze the correlation between VOCs and environmental factors, geochemical analyses indicated that nitrate (NO3−) and sulfate (SO42−) served as electron acceptors in the anaerobic biodegradation of organic pollutants, with bicarbonate (HCO3−) levels increasing as a result of this biodegradation. Additionally, the curved streamline searchlight shaped model (CS-SLM) was applied to identify the primary land use types affecting VOCs content, construction land and cropland were primary land use types affecting VOCs distribution. Finally, the ecological risk assessment indicated the highest risk quotient (RQ) for styrene (0.21), suggesting a manageable risk level. The study emphasizes the complexity of VOCs contamination in groundwater, providing a foundation for targeted mitigation strategies.

Development and validation of hydrophobic molded pulp nursery pots made of hemp hurd

Biodegradable nursery pots (BNPs) composed of 50 % hemp hurd and 50 % recycled cardboard fibers (w/w dry basis) were produced using a custom-built handheld molded pulp device. Milling followed by sequential peracetic acid and sodium hydroxide delignification treatment reduced lignin content of hemp hurd from 23.76 % to 2.39 %, liberating cellulose and hemicellulose fibers for enabling the formation of interfiber interactions in molded pulp formulations. Beeswax and precipitated calcium carbonate based hydrophobic coating at ~10 μm thickness significantly enhanced hydrophobicity of the BNPs, as indicated by the surface contact and sliding angle of 116.25° and 34.82°, respectively. Anaerobic biodegradability of BNP was confirmed via carbon dioxide and methane gas accumulation measurements. Developed BNPs were successfully validated through an eleven week greenhouse planting trial. This study introduced a new biodegradable molded pulp formulation made from hemp hurd and validated its application as an alternative to single use plastic nursery pots for growing seedlings.

Valorization of paper-mill sludge laden with 2-chlorotoluene using hydroxyapatite@biochar nanocomposite to enrich methanogenic community: A techno-economic approach

While several studies have investigated the anaerobic digestion of paper-mill sludge (PMS), this technology suffers from nutrient insufficiency, inhibition by aromatic compounds, and low bio-CH4 yield. Hence, PMS was anaerobically co-digested with chicken manure (CM) and supplemented by hydroxyapatite@biochar (HAP@BC) nanocomposite for enhancing 2-chlorotoluene degradation and enriching the methanogenic archaea. Multiple continuous stirred tank reactors (CSTRs) were operated at 12.6 h hydraulic retention time (HRT), using PMS (R1), CM (R2), PMS + CM (R3), PMS + CM+100 mg HAP/L (R4), and PMS + CM+100 mg HAP@BC/L (R5). The maximum bio-CH4 yield of 147.5 ± 9.1 mL/g COD and 2-chlorotoluene removal of 91.2 ± 6.8 % were obtained from R5, experiencing a sufficient C/N ratio of 14.7 and the highest activities of acidogenesis (42.0 %), acetogenesis (37.9 %), and methanogenesis (42.1 %). The abundances of Euryarchaeota, Bacteroidota, and Chloroflexi at the phylum level, and Pseudomonas, and Bacillus at the genus level could highly contribute to the dechlorination mechanism and acetate transformation into CH4. This biomass-to-bioenergy project (10 m3/d capacity) could benefit from pollution reduction, biogas recovery, and carbon credit, giving 5.6 yr payback-period, 3503 USD net present value, and 12.1 % internal rate of return. Because R5 exhibited an efficient techno-economic anaerobic biodegradation performance, future studies are required to optimize its HRT condition and HAP@BC dosage.

Enhancement of the anaerobic biodegradation efficiency of azo dye by anthraquinone-loaded biochar biofilm: factors affecting biofilm formation and the enhancement mechanism

Carbon-based materials that serve as microbial carriers, and the role of surface-formed biofilms in anaerobic digestion, merit further investigation. This study explored the role and mechanism behind the biodegradation enhancement of biofilms formed onto anthraquinone-loaded biochar (AQS-BC) surfaces through the anaerobic decolorization process of azo dye Reactive Red 2, and optimized the conditions for AQS-BC biofilm formation. The results indicated that the AQS-BC biofilm system exhibited high treatment efficiency and stability in RR2 anaerobic decolorization. RR2 led to the accumulation of volatile fatty acids (VFAs) and inhibition of methane production, while the presence of AQS increased methane production. The effects of sludge concentration, contact time, carbon source concentration, and RR2 concentration on biofilm maturity were also analyzed. Combining biochemical characteristics, electrochemical properties, surface structure, and microbial community analysis, a mechanism for the anaerobic decolorization of RR2 via AQS-BC as a microbial carrier was proposed. This study provides insights into the roles of biofilms in the anaerobic wastewater treatment processes.Graphical

Stimulation of Batch Mesophilic Anaerobic Digestion by Cellulose- and Polysaccharide-Derived Polymers in Landfill Leachates

The fate of biobased and biodegradable cellulose-derived plastics in landfills represents an important topic from economic and environmental points of view. Anaerobic digestion is a cost-effective waste-to-energy technology. The behaviour of six polymer types—that is, cellulose (C), cellulose acetate (CA), viscose (V), nanocellulose (NC), acetate textile (AT), and heteropolysaccharide pectin (P)—was studied under anaerobic batch mesophilic conditions in a landfill leachate for 147 days. The cumulative biogas production was as follows: C>V=CA>>AT>>NC=P. Metagenomic analysis revealed notable variations in the proportion of bacterial and archaeal domains with the highest archaeal abundance in the presence of CA (80.2%) and C (78.5%). At the end of digestion, cellulolytic, hydrolytic, and dehydrogenase activities were measured in the intact samples, as well as the liquid and solid fractions, under aerobic and anaerobic conditions. Cellulolytic activity in P was detected only in the pellet, while in NC, activity was mostly in the supernatant under both aerobic and anaerobic conditions. Scanning electron microscopy and confocal scanning laser microscopy showed a defragmentation and degradation of polymeric substrates as well as microbial colonisation. Based on the results, landfill leachate is appropriate for the anaerobic biodegradation of cellulose-derived polymers; however, the process is polymer specific.

Enhanced biogas production from municipal solid waste via digestion with cow manure: A case study

Abstract Anaerobic digestion (AD) of feedstocks yields biogas, a potentially useful new energy source. This study looked into the anaerobic co-digestion of cow dung and organic garbage to produce biogas. An anaerobic biodigester, with a volume of 20 L, was used to digest organic waste (OW) and to trace the changes that occur during the AD process. It was equipped with tools that ensure complete control of the conditions affecting anaerobic biological reactions such as temperature, pH function, and mixing speed. Therefore, an anaerobic biodigester was designed to contain such biological transformations and to improve the biogas production process from OW. Based on the present investigation, the AD of OW was improved by integrating the substrate with sewage sludge or cow manure (CM) during the digestion process to provide the basic microorganisms to complete the digestion process. Feeding into the digester was a blend of 100 kg of cow dung (CM) and OW per day, diluted 1:1 with water. A gasbag was used to capture the methane that resulted. Biogas production began on the seventh day after the substrate was fed into the digester. A performance test was carried out on the produced biogas to determine its composition. For OW–CM, the generated biogas’s methane (CH4) concentration was determined to be 60%, but the rates of decline for TS and VS were 57 and 50.6%, respectively. Anaerobic biodegradation of OW–CM experiments was observed at 37°C, a mesophilic temperature. For OW–CM, the pH value was 6.7. After being adjusted to standard circumstances, the cumulative volume of methane produced which had been recorded as 4,914 mL became 3964.5 mL.

Anaerobic Degradation of Aromatic and Aliphatic Biodegradable Plastics: Potential Mechanisms and Pathways.

Biodegradable plastics (BDPs) have been widely used as substitutes for traditional plastics, and their environmental fate is a subject of intense research interest. Compared with the aerobic degradation of BDPs, their biodegradability under anaerobic conditions in environmental engineering systems remains poorly understood. This study aimed to investigate the degradability of BDPs composed of poly(butylene adipate-co-terephthalate) (PBAT), poly(lactide acid) (PLA), and their blends, and explore the mechanism underlying their microbial degradation under conditions of anaerobic digestion (AD). The BDPs readily depolymerized under thermophilic conditions but were hydrolyzed at a slow rate under conditions of mesophilic AD. After 45 days of thermophilic AD, a decrease in the molecular weight and significant increase in the production of methane and carbon dioxide production were observed. Network and metagenomics analyses identified AD as reservoirs of plastic-degrading bacteria that produce multiple plastic-degrading enzymes. PETase was identified as the most abundant plastic-degrading enzyme. A potential pathway for the anaerobic biodegradation of BDPs was proposed herein. The polymers of high molecular weight were subjected to abiotic hydrolysis to form oligomers and monomers, enabling subsequent microbial hydrolysis and acetogenesis. Ultimately, complete degradation was achieved predominantly via the pathway involved in the conversion of acetic acid to methane. These findings provide novel insight into the mechanism underlying the anaerobic degradation of BDPs and the microbial resources crucial for the efficient degradation of BDPs.

Single-cell Protein Bioplastic Films from Recovered Nitrogen and Carbon with High Anaerobic Biodegradability and Biogas Potential at End-of-Life

Single-cell Protein Bioplastic Films from Recovered Nitrogen and Carbon with High Anaerobic Biodegradability and Biogas Potential at End-of-Life

Wheat Bran and Saccharomyces Cerevisiae Biomass’ Effect on Aerobic and Anaerobic Degradation Efficiency of Paper Composite

This study is a continuation of research on sustainable food packaging materials made from locally available feedstock and industrial by-products within the Baltic Sea region. Its main focus is the impact of wheat bran filler and Saccharomyces cerevisiae additive, which was used to develop a novel bio-coating for paper composite packaging, on the biodegradation efficiency of paper composites under aerobic and anaerobic conditions. In this study, we analyzed the effect of 15% and 40% concentrations of wheat bran filler and Saccharomyces cerevisiae biomass on the biodegradation efficiency of paper composites. This research was conducted under controlled environmental conditions, with aerobic biodegradation tested at 46 °C in a compost-based mesophilic–thermophilic environment and anaerobic biodegradation tested at 55 °C in an active inoculum thermophilic environment. The results show that the presence of wheat bran filler significantly improves biodegradation efficiency compared to microcrystalline cellulose reference material. Under aerobic conditions, the biodegradation efficiency for the 40% wheat bran and yeast sample was 6.34%, compared to only 0.71% for the cellulose reference material. In anaerobic conditions, the 15% wheat bran and yeast sample showed a biodegradation efficiency of 96.62%, compared to 82.32% for the cellulose reference material.

Anaerobic biodegradation of real pharmaceutical-grade lactose manufacturing wastewater in a modified Internal Circulation Reactor

Pharmaceutical-grade lactose (PL) manufacturing generates wastewater containing high concentrations of biodegradable organic matter. In the absence of a suitable alternative, industries handle such concentrated streams by completely evaporating the entire stream and disposing of water-soluble solid residue in a landfill. Such a process is energy-intensive, and nothing useful is recovered from the stream. This study demonstrates the efficient and sustainable anaerobic biodegradation of real PL wastewater using a lab-scale internal circulation reactor (ICR) combined with an external recirculation system. The effects of feed Chemical Oxygen Demand (COD) concentration, organic loading rate (OLR), and hydraulic retention time (HRT) on COD removal efficiency, methane production, and the volatile fatty acids/alkalinity (VFA/ALK) ratio were evaluated. Under the highest feed COD concentration of 60,000mg/L, OLR of 4.5kg/m³∙d, and HRT of 13.33 days, the system achieved an average COD removal efficiency of 93.8% with methane production of 25.2L/d (specific methane generation of 0.32L/g CODremoved). By increasing the up-flow velocity from 0.044m/h (without external recirculation) to 1.5m/h (with external recirculation), COD removal improved from 63.6% to 93.4%, and methane production increased from 7.5L/d to 14L/d. The kinetics of COD removal fitted well in the modified Stover-Kincannon model (R2 = 0.99). A unique finding of this study is that the loose anaerobic sludge became granulated after 120 days, with 50% of the granules having diameters ≥ 2.0mm. The results of this study establish anaerobic biodegradation as a suitable treatment option for PL wastewater, thereby achieving UNSDG 6 (Clean Water and Sanitation) and 7 (Affordable and Clean Energy).

Divergent dual C-H isotopic fractionation pattern during anaerobic biodegradation of toluene within Aromatoleum species under nitrate-reducing conditions

Toluene is a pollutant frequently detected in contaminated groundwater, mostly due to leakage from underground gasoline storage tanks and pipeline ruptures. Multi-element compound-specific isotope analysis provides a framework to understand transformation processes and design efficient remediation strategies. In this study, we enriched an anaerobic bacterial culture derived from a BTEX-contaminated aquifer that couples toluene and phenol oxidation with nitrate reduction and the concomitant production of carbon dioxide and biomass. The 16S rRNA gene amplicon data indicated that the toluene-degrading consortium was dominated by an Aromatoleum population (87 ± 2 % relative abundance), and metagenome sequencing confirmed that the genome of this Aromatoleum sp. encoded glycyl-radical enzyme benzylsuccinate synthase (BssABC) and phenylphospate synthase (PpsA1BC) homologous genes involved in the first step of toluene and phenol transformation, respectively. Carbon and hydrogen isotopic fractionation were εbulk, C = - 3.5 ± 0.6 ‰ and εrp, H = - 85 ± 11 ‰, respectively, leading to a dual C-H isotope slope of ΛH/C = 26 ± 2. This value fits with a previously reported value for a consortium dominated by an Azoarcus species (ΛH/C = 19 ± 5) but differs from that reported for Aromatoleum aromaticum (ΛH/C = 14 ± 1), both of which grow with toluene under nitrate-reducing conditions. Overall, this suggests the existence of different BssABC enzymes with different mechanistic motifs even within the same Aromatoleum genus.

Optimizing intermittent micro-aeration as a strategy for enhancing aniline anaerobic biodegradation: kinetic, ecotoxicity, and microbial community dynamics analyses.

Groundwater and soil contamination by aromatic amines (AAs), used in the production of polymers, plastics, and pesticides, often results from improper waste disposal and accidental leaks. These compounds are resistant to anaerobic degradation; however, micro-aeration can enhance this process by promoting microbial interactions. In batch assays, anaerobic degradation of aniline (0.14 mM), a model AA, was tested under three micro-aeration conditions: T30, T15, and T10 (30, 15, and 10 min of micro-aeration every 2 h, respectively). Aniline degradation occurred in all conditions, producing both aerobic (catechol) and anaerobic (benzoic acid) byproducts. The main genera involved in T30 and T15 were Comamonas, Clostridium, Longilinea, Petrimonas, Phenylobacterium, Pseudoxanthomonas, and Thiobacillus. In contrast, in T10 were Pseudomonas, Delftia, Leucobacter, and Thermomonas. While T30 and T15 promoted microbial cooperation for anaerobic degradation and facultative respiration, T10 resulted in a competitive environment due to dominance and oxygen scarcity. Despite aniline degradation in 9.4 h under T10, this condition was toxic to Allium cepa seeds and exhibited cytogenotoxic effects. Therefore, T15 emerged as the optimal condition, effectively promoting anaerobic degradation without accumulating toxic byproducts. Intermittent micro-aeration emerges as a promising strategy for enhancing the anaerobic degradation of AA-contaminated effluents.

Simulation of anaerobic biodegradation process in a tubular bioreactor with a biofilm layer: Steady-state and unsteady-state conditions

In this paper, anaerobic biodegradation process in a tubular bioreactor with an inner biofilm layer for steady-state and unsteady-state conditions are simulated. The effects of various parameters including bioreactor diameter, fraction of active biomass transferred to liquid phase, and residence time of the liquid on bioreactor performance are examined. Simulations indicate that decreasing diameter of bioreactor leads to increasing degree of conversion of the substrate in liquid phase and decreasing dimensionless concentration of the substrate in biofilm. With an increase in the fraction of active biomass transferred to liquid, substrate concentrations in liquid and biofilm slightly vary. Increased residence time of the liquid phase results in the degree of conversion of substrate goes up, but substrate concentration in biofilm lowers a little. In addition, it is found that biomass concentration of liquid phase is boosted with decreased bioreactor diameter and increased residence time of liquid. A proportional-integral controller is designed and the tuned parameters of KP=−0.131 and KI=0.02 are obtained using genetic algorithm. It is observed that controller regulate well the degree of conversion of the substrate within 120 s for both servo and regulatory modes.

A novel strategy combining hydrogenotrophic methanogens' bioaugmentation and biochar biostimulation for simultaneous polycyclic aromatic hydrocarbon biodegradation and bioenergy recovery.

A novel strategy combining bioaugmentation using methanogenic archaea and biostimulation using biochar was proposed for the first time to obtain simultaneous improvement of mixed PAHs' anaerobic biodegradation and bioenergy production. The results showed that the addition of PHAs immediately resulted in inhibition in methane production and accumulation of VFA, indicating that PHAs are more toxic to methanogens than the acetogenic bacteria. The coupling of biochar with hydrogenotrophic methanogen alleviated the inhibitory effects of PAHs, allowing the anaerobic fermentation system to recover its methane production capability rapidly. Compared to the Fe3+ + bioaugmentation group, the biochar + bioaugmentation group exhibited a 7.5% higher restored cumulative methane production. This coupling strategy ultimately facilitated the degradation of most PAHs, achieving a removal rate of over 90%. Moreover, the coupled biochar and bioaugmentation induced significant changes in the archaeal community structure. Direct interspecies electron guilds (i.e., Streptococcus and Methanosarcina) were enriched in the presence of biochar and bioaugmentation, responsible for prominent PAH removal and methane recovery. This study demonstrated the feasibility of simultaneous PAH biodegradation and bioenergy production using electron acceptor and enriched microorganisms.

Pig manure degradation and carbon emission: Measuring and modeling combined aerobic-anaerobic transformations.

Greenhouse gas emissions from liquid livestock manure storage significantly contribute to global warming. Accurate farm-scale models are essential for predicting these emissions and evaluating manure management strategies, but they rely on multiple parameters describing carbon loss dynamics. Surface respiration may significantly influence carbon loss and methane emission, yet it is not explicitly included in current models. We conducted experiments to measure pig manure surface respiration rate and its effect on organic matter degradation and methane and carbon dioxide emissions. Manure was incubated for 283 days at 10°C or 20°C under aerobic or anaerobic conditions, while measuring methane and carbon dioxide emission. This was followed by anaerobic digestion at 38°C. Surface respiration reduced the organic matter content, and the effect was temperature dependent. Methane emission was not affected by surface respiration, suggesting that substrate availability was not rate-limiting for methanogenesis. Surface respiration rates were 18.1±3.5g CO2 m-2 day-1 at 10°C and 37.1±13.1g CO2 m-2 day-1 at 20°C (mean±standard deviation) and were consistent with microsensor measurements of oxygen consumption in different manure surfaces. Based on these results, temperature- and surface area-dependent respiration was incorporated in the existing anaerobic biodegradation model (ABM). Simulations showed that surface respiration accounts for 29% of carbon losses in a typical pig house and 8% for outdoor storage. Developing and refining algorithms for diverse carbon transformations, such as surface respiration, is crucial for evaluating the potential for methane emission and identification of variables that control emissions at the farm scale.

Meta-Analysis and Machine Learning Models for Anaerobic Biodegradation Rates of Organic Contaminants in Sediments and Sludge.

Anaerobic biodegradation rates (half-lives) of organic chemicals are pivotal for environmental risk assessment and remediation. Traditional experimental evaluation, constrained by prolonged, oxygen-free conditions, struggles to keep pace with emerging contaminants. Data-driven machine learning (ML) models serve as promising complements. However, reported quantitative structure-biodegradation relationships or ML models on anaerobic biodegradation are mostly based on small data sets (<100 records) and neglect experimental conditions, usually achieving compromised predictions. This work aimed to develop ML models for predicting the biodegradation half-lives of organic pollutants in anaerobic environments (i.e., sediment/soil and sludge). Focusing on important features of both chemicals and experimental conditions, we first curated two data sets, one for sediment/soil (SED) and the other for sludge (SLD), covering 978 records for 206 chemicals from the literature, and then conducted a meta-analysis. Next, we built a binary classification (half-life of 30 days as the cutoff) model with an accuracy of 81% and a regression model with R2 of 0.56 for SED based on LightGBM (80% and 0.31 for SLD based on Extra tree, respectively). The model interpretations underscored the significance of experimental conditions (e.g., temperature and inoculum dosage), as evidenced by their high feature importance, and the models were found to correctly capture the effects of chemical substructures, for example, branched structures and aromatic rings prolonged half-lives while methyl group and ortho-substitution on rings shortened half-lives. The applicability domains of the models were also defined, resulting in reasonable prediction for the half-lives of 41% (SED) or 67% (SLD) of over 4000 persistent, bioaccumulative, and toxic chemicals. Overall, this study pioneers ML models for predicting the anaerobic degradation half-lives, offering valuable support for future evaluation and implementation of chemical anaerobic biodegradation.

Investigation of solid waste generation rate and biogas production

Anaerobic Digestion (AD) of organic waste is one of the most promising processes and is the ideal solution for the disposal of organic waste (OW) and at the same time, the production of methane gas which may be used as a sustainable energy resource. An anaerobic biodigester with a volume of (20) liters has been used to digest organic waste and to trace the changes that occur during the AD process. Operating parameters such as temperature, pH, total solids, and volatile solids (TS, VS) have been measured which have a significant impact on the rate and quality of biogas production. Experiments on anaerobic biodegradation of OW-SS were monitored under mesophilic conditions (temperature 37 °C, retention time 30–31 days). The pH value varied between (4.2–5.8) for OW-SS. During 30 days of the detection period, the maximum methane production (corrected) occurred on day 21 which was equal to 254.3-ml. The cumulative volume of the produced methane was recorded as (3409 ml), OW-SS, and these results were corrected to the standard conditions, where after correction, it became (2929 ml). The highest rate of methane concentration was estimated at (52 %) for OW-SS, while the rate of decrease in the TS and VS was (54 %, and 45 %), respectively. It is recommended to examine the changes that occur if a larger digester is used than the one used in the current study, such as 50 L, 100 L …. Etc. To compare the data obtained in this study with the results of larger digestions to allow for the opportunity to build anaerobic digesters at the plant level with the benefit of renewable energy production. It is also recommended to investigate the impact of some types of pretreatments on biogas production such as the use of alkali, enzymatic, ultrasonic treatment or acid ton the solid waste feed.

A dual-function mixed-culture biofilm for sulfadiazine removal and electricity production using bio-electrochemical system

Sulfadiazine (SDZ) is frequently detected in environmental samples, arousing much concern due to its toxicity and hard degradation. This study investigated the electricity generation capabilities, SDZ removal and microbial communities of a highly efficient mixed-culture system using repeated transfer enrichments in a bio-electrochemical system. The mixed-culture biofilm (S160-T2) produced a remarkable current density of 954.12 ± 15.08 μA cm−2 with 160 mg/L SDZ, which was 32.9 and 1.8 times higher than that of Geobacter sulfurreducens PCA with 40 mg/L SDZ and without additional SDZ, respectively. Especially, the impressive SDZ removal rate of 98.76 ± 0.79% was achieved within 96 h using the further acclimatized mixed-culture. The removal efficiency of this mixed-culture for SDZ through the bio-electrochemical system was 1.1 times higher than that using simple anaerobic biodegradation. Furthermore, the current density and removal efficiency in this system gradually decreased with increasing SDZ concentrations from 0 to 800 mg/L. In addition, community diversity data demonstrated that the dominant genera, Geobacter and Escherichia-Shigella, were enriched in mixed-culture biofilm, which might be responsible for the current production and SDZ removal. This work confirmed the important roles of acclimatized microbial consortia and co-substrates in the simultaneous removal of SDZ and electricity generation in an electrochemical system.

Enrichment of Polycyclic Aromatic Hydrocarbon (PAH)-Degrading Strictly Anaerobic Sulfate-Reducing Cultures from Contaminated Soil and Sediment.

Sulfate-reducing bacteria (SRB) are crucial players in global biogeochemical cycling and some have been implicated in the anaerobic biodegradation of organic pollutants, including recalcitrant and hazardous polycyclic aromatic hydrocarbons (PAHs). Obtaining PAH-degrading SRB cultures for laboratories is of paramount importance in the development of the young field of anaerobic biodegradation of PAHs. SRB grow exceptionally slowly on PAH substrates and are highly sensitive to oxygen. Consequently, enrichment and maintenance of PAH-degrading SRB cultures and characterization of the biodegradation process remain a tedious and formidable task, especially for new researchers. To address these technical constraints, we have developed robust and effective protocols for obtaining and characterizing PAH-degrading SRB cultures. In this set of protocols, we describe step-by-step procedures for preparing inocula from contaminated soil or sediment, preparing anoxic medium, establishing enrichment cultures with PAHs as substrates under completely anaerobic sulfate-reducing conditions, successive culture transfers to obtain highly enriched cultures, rapid verification of the viability of SRB in slow-growing cultures, assessment of PAH degradation by extracting residuals using organic solvent and subsequent analysis by gas chromatography-mass spectrometry, and spectrophotometric determination of sulfate and sulfide in miniaturized, medium-throughput format. These protocols are expected to serve as a comprehensive manual for obtaining and characterizing PAH-degrading sulfate-reducing cultures. © 2024 The Author(s). Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Obtaining PAH-degrading strictly anaerobic sulfate-reducing enrichment cultures from contaminated soil and sediment Support Protocol 1: Operation and maintenance of an anaerobic workstation Support Protocol 2: Setup of gas purging systems for preparing anoxic solutions Support Protocol 3: Verification of viability in slow-growing SRB enrichment cultures Support Protocol 4: Extraction of genomic DNA from low-biomass cultures Basic Protocol 2: Extraction of residual PAH from liquid culture and analysis by GC-MS Basic Protocol 3: Spectrophotometric determination of sulfate concentration in SRB cultures Basic Protocol 4: Spectrophotometric determination of sulfide concentrations in SRB cultures by the methylene blue method Alternate Protocol: Spectrophotometric determination of sulfide concentrations in SRB cultures by the colloidal copper sulfide method.

Food waste impact on dry anaerobic digestion of straw in a novel reactor: Biogas yield, stability, and hydrolysis-methanogenesis processes

Gradient anaerobic digestion reactor (GADR) can improve substrate utilization efficiency by solving the problem of the “short circuit” of materials. However, the substrate’s composition significantly affects the reactor’s performance. This study investigated the impact of food waste (FW) levels on corn straw’s dry anaerobic digestion (AD) in a novel GADR. The results show that biomethane production can be improved by coupling urban and agricultural solid waste recycling. The mechanism is to increase the hydrolysis and acid production efficiency, and the abundance of enzymes related to methanogenesis. The maximum methane yield (494.2 mL CH4/g VS) and the highest anaerobic biodegradability (85.7 %) were obtained when the FW was added at 60 %. The co-digestion of FW and straw can improve the hydrolysis and acid production efficiency and methane yield, which improves the buffering capacity and stability of the system compared with the single digestion of FW.