Consortium Of Sulfate-reducing Bacteria Research Articles

Anaerobic bioremediation of acid phosphogypsum stacks leachates: Assessment of leachate’s biochemical changes and microbial community dynamics

Phosphogypsum (PG) is the largest by-product of the phosphate industry. Nearly 300 M tons of PG are annually discarded, of which 58% is dry stacked. The exposure of PG stacks to rainwater and processed waters moisture creates hydraulic pressure, generating acidic PG leachates into nearby aquifer systems. Because of its elevated levels of sulfates, phosphorus (P) and metals, the PG water leachate can negatively affect the surrounding environments. This work investigates the effect of water activity on the PG leaching, by studying the effect of different PG:Water ratios on the leaching process, followed by the anaerobic bioremediation of PG leachate through biological sulfate removal activity (BSRA). This later involves using sulfate-reducing bacteria consortium within an anaerobic bioreactor, allowing a simultaneous monitoring of the leachate’s biochemical changes, impurities removal, and microbial community dynamics. The results determined the highest sulfates and impurities leaching from PG with a PG:Water ratio of 1:200 (w:v). Subsequently, the biological treatment of the leachate exhibited an efficient removal of sulfates (79%), P (99%) and chemical oxygen demand (93%), with a substantial decline in metal concentrations (Cd, As and Al by 99%, and Zn by 70%) from the leachate. Moreover, the acidity of the leachate was also neutralized through the BSRA process by increasing the pH from 4 to 7.52. Furthermore, the microbial community dynamics unveiled a significant correlation between the leachate’s biochemical changes and co-existence of specific sulfate-reducing bacteria within various bacterial phyla, including Desulfobacterota, Firmicutes, and Proteobacteria, allowing efficient and eco-friendly bioremediation process of PG leachate.

Effectivity of anaerobic deposition reactor (ADR) based on sulphate reducing bacteria for laboratorium wastewater treatment

Laboratory wastewater is classified as hazardous waste that is disposed of into the environment and will be very risky to environmental health. In this study, the use of a consortium of Sulphate Reducing Bacteria (SRB) was studied which was grown simply in an anaerobic column. SRB suspension was applied to the prototype anaerobic bioreactor to treat of laboratory wastewater with containing heavy metals and acidic. SRB was grown in medium of fermented compost and Postgate’s B. This research formulated that the SRB solution nursery as the optimal bioreactor activator after 15 days with the composition of the growth medium consisting of Postgate B solution (65%), Fermented compost liquid (30%) and active suspension liquid (5%), with a total population of cell colonies reaching 1.2 x 105 CFU/mL. The bioreactor requires an adjustment process for 15 days, after which the sulphate and heavy metal ion reduction process occurs significantly, and is effective with the combination of fermented compost content with the right Postgate solution, and a bioreactor with 30% compost fermented effective in reducing Pb metal ions, but for Cu and Fe metal ions were only effective after 7 days of adjustment.

Harnessing sulfate-reducing bacteria with plants growing to revitalize metal-tainted coal mine soils in Midwest China: metal sequestration performance, ecological networking interaction, and functional enzymatic prediction.

Heavy metal contamination from coal mining calls for advanced bioremediation, i.e., using sulfate-reducing bacteria (SRB) technology. Yet, the interaction of SRB with native soil microbiota during metal sequestration, especially in the presence of plants, remains ambiguous. In this study, we assessed the metal sequestration capabilities, ecological network interactions, and enzymatic functions in soils treated with a predominant SRB consortium, mainly Desulfovibrio (14 OTUs, 42.15%) and Desulfobulbus (7 OTUs, 42.27%), alongside Acacia dealbata (AD) and Pisum sativum (PS) plants. The SRB consortium notably enhanced the immobilization of metals such as Zn, Cu, As, and Pb in soil, with the conversion of metals to residual forms rising from 23.47 to 75.98%. Plant inclusion introduced variability, potentially due to changes in root exudates under metal stress. While AD flourished, PS demonstrated significant enhancement in conjunction with SRB, despite initial challenges. Comprehensive microbial analyses revealed the pivotal role of SRB in influencing microbial networking, underpinning critical ecological links. This interplay between plants and SRB not only enhanced microbial diversity but also enriched soil nutrients. Further, enzymatic assessments, highlighting enzymes like NADH:ubiquinone reductase and non-specific serine/threonine protein kinase, reinforced contribution of SRB to energy metabolism and environmental resilience of the entire soil microbial community. Overall, this research underscores the potential of SRB-driven bioremediation in revitalizing soils affected by coal mining.

Nondestructive, reagent-free, low-volume fluidic set-up to study biofilms by using a transparent electrode, allowing simultaneous electrochemical and optical measurements.

The aim was to develop an electrochemical/optical set-up and correlate it (as validation) with other chemical and physical methods to obtain a simple and cost-effective system to study biofilm formation. A simple microfluidic cell and methods allowed continuous monitoring of the first, critical steps of microbial attachment. We monitored sulfate-reducing bacteria (SRB) at the early stages of biofilm formation. Herein, we studied the formation and adherence of SRB consortium biofilms over an indium tin oxide (ITO) conducting surface using microbiological and chemical methods, microscopic observations [scanning electron microscopy (SEM) and optical], and electrochemical impedance spectroscopy (EIS) measurements. The SRB biofilm formation was evaluated for 30 d by SEM and EIS. Charge transfer resistance decreased when the microbial population colonized the electrode. The monitoring of early-stage biofilm formation was performed using EIS at a single frequency of 1Hz during the first 36 h. The simultaneous use of optical, analytical, and microbiological methods allowed us to connect the kinetics of the growth of the microbial consortium to the values obtained via the electrochemical technique. The simple setup we present here can help laboratories with limited resources to study biofilm attachment and facilitates the development of various strategies to control biofilm development in order to avoid damage to metallic structures (microbiologically influenced corrosion, MIC) or the colonization of other industrial structures and medical devices.

Chromium bioremediation of batik industrial wastewater using a consortium of sulfate-reducing bacteria from forested wetland soil

Chromium pollutants in textile wastewater can be removed by bioremediation using sulfate-reducing bacteria (SRB) from forested wetland soil. Biostimulation of carbon sources in the form of molasses and a supporting material in the form of zeolite to trap bacteria and create biofilms can improve the ability of SRB to bioremediate chromium. The batch bioremediation technique was further examined by including molasses, a combination of molasses and zeolite, and SRB, which has been adapted to acclimatize wastewater that is diluted two times. Adaptive SRB aged 7 days, which had reached the exponential growth phase, showed optimal bioremediation activity when molasses and zeolite were added. Results of further observations of the consortium on continuous bioremediation with the same treatment showed decontamination of chromium efficiency that reached about 94%. In addition, pH values decreased efficiency at approximately 7.3 in 14 days of incubation. The biological oxygen demand, chemical oxygen demand, and sulfate concentrations also decreased at around 89%, 92%, and 91%, respectively. SRB immobilization with zeolite-induced biofilm formation was observed at 9 days, and it further increased at 14 days. SRB cells observed were attached to the surface of the zeolite, between cells connected to each other by extracellular polymeric substances. The mass of sulfur and chromium on the surface of the zeolite increased from the 9th and 14th days. Sulfur increased from 0.07% to 0.27%, whereas chromium increased from 0.21% to 0.84%. The increase in the percentage of the two elements on the zeolite surface indicated the decontamination of sulfate and chromium pollutants in wastewater.

Pengaruh Nitrat terhadap Biokorosi Logam oleh Konsorsium Bakteri Pereduksi Sulfat dari PLTA Saguling

<div><strong>The Influence of Nitrate in Metal Biocorrosion caused by Sulfate Reducing Bacteria from Saguling Hydropower</strong>. The corrosion facilitated and accelerated by the activities of microorganism is called biocorrosion. Sulfate reducing bacteria (SRB) is known as the bacteria that cause biocorrosion in anaerobic condition by using sulfate as the final electron acceptor. Biocorrosion reduces equipment lifetime and increases maintenance cost in industry. In the cooling system in Saguling hydropower, corrosion was commonly caused by utilization of contaminated water due to anorganic and organic waste, especially sulfate. In this research, sulfate reducing bacteria was isolated from biofilms in the cooling system of Saguling Hydropower. Molecular analysis using PCR-DGGE method with dsrB gene (350 bp) as molecular markers showed that SRB consortium contained 12 bands and assumed as different species of SRB. SRB consortium was tested to determine its biocorrosion activity over metal material of ST37 (carbon steel) and SUS304 (stainless steel). The consortium then treated with 7 different nitrate concentrations to determine its effect against the sulfate reducing bacteria activity. SRB consortium caused higher corrosion to ST37 than SUS304L, with the corrosion rate of 0.07660 mm/year and 0.00265 mm/year, respectively. Concentration of 10 mM nitrate effectively inhibited corrosion rate on ST37 and caused the changes in sulfate reducing bacteria communities, indicated by the disappearance of 6 bands in DGGE profile</div>

Integrative effect of citrate on Cr(Ⅵ) and total Cr removal using a sulfate-reducing bacteria consortium

In controlling toxic Cr(Ⅵ) pollution, the sulfate-reducing bacteria (SRB) method—a bioresource technology—is considered more sustainable and stable than synthetic technologies; however, its mechanisms of metal removal are unclear. This study investigated the mechanism of the use of citrate as a carbon source in an SRB bioreactor for Cr(Ⅵ) removal by disassemble or simulation approach. We show that citrate can mask toxicity, whereby the IC50 value (inhibitory concentration affecting 50% of the test population) of citrate was higher than that of lactate, and that citrate can also protect water systems from oxidation. The anti-oxidation rate of citrate ranged from 76.00% to 90.92%; whereas for citrate‒Cr(Ⅲ), the oxidation rate was only 0.185%–0.587%. Citrate can up-regulate microbial genes and functions, causing acetate and sulfide (NaFeS2) accumulation. Acetate addition promoted Cr adsorption by sulfide (mainly NaFeS2) and promoted sulfide sedimentation. Moreover, in addition to Cr(Ⅵ) reduction and Cr(Ⅲ)‒sulfide generation, the addition of sulfide promoted sedimentation; the correlation coefficient between the sedimentation coefficient and the sulfur content was r = −0.88877 at p < 0.01. Therefore, citrate had a systemic radiative effect on every aspect of the SRB‒citrate system model for Cr(Ⅵ) removal. In addition to the reduction in the former simple model, an integrative effect (including adsorption, sedimentation, and metabolism) was combined with NaFeS2 for Cr removal, which was regulated by the SRB‒citrate system. Exploration and understanding of these mechanisms promote SRB‒citrate methods to be wider implications in practice.

Modelling a rotating biological contactor treating heavy metal contaminated wastewater using artificial neural network

Abstract The performance of a continuously operated laboratory-scale rotating biological contactor (RBC) was assessed for the removal of heavy metals viz. Cu(II), Cd(II) and Pb(II) from synthetic wastewater using artificial neural networks (ANNs). The RBC was inoculated with Sulfate Reducing Bacteria consortium (predominantly Desulfovibrio species), and the performance was evaluated at different hydraulic retention times (HRTs) and inlet heavy metal concentrations. A feed-forward back-propagation neural network model was developed using 90 data sets obtained over a period of three months, to predict the removal of heavy metal (HMRE) and COD (CODRE). The predictive capability of the model was evaluated in terms of the coefficient of determination (R) and mean absolute percentage error between the model fitted and actual experimental data, whereas sensitivity analysis was performed on the input parameters by determining the absolute average sensitivity (AAS) values. The higher AAS value of the HRT compared with that of inlet heavy metal concentration suggested that the change of HRT has a significant influence on HMRE and CODRE. Overall, the results obtained from this study demonstrated that ANNs can efficiently predict RBC behaviour with regard to heavy metal and COD removal characteristics under the prevailing operational conditions.

Microbial Corrosion of C1018 mild steel by a halotolerant consortium of sulfate reducing bacteria isolated from an Egyptian oil field

In this study, a consortium of halotolerant sulfate reducing bacteria (SRB) was obtained from a water sample collected from an Egyptian oil-field. North Bahreyia Petroleum Company (NORPETCO) is one of the petroleum companies that suffer from severe corrosion. The present study aim to investigate the microbial structures of this consortium and their potential contributed to microbial corrosion. Dissimilatory sulfite reductase dsrAB gene sequences analysis indicated that the mixed bacterial consortium contained two main phylotypes: members of the Proteobacteria (Desulfomicrobium sp., Desulforhopalus sp., and Desulfobulbus sp.) and Firmicutes (Desulfotomaculum sp.). Mild steel C1018 coupons were incubated in the presence of SRB consortium for a period of 35 days, the evolution of corrosion was studied using weight loss and dissolved sulfide production of SRB consortium. Results indicated that, the corrosion rate in the presences of SRB was approximately 15 times of that for the control. Furthermore, sessile cells (biofilm) and subsequent corrosion products that developed were characterized by scanning electron microscope coupled with energy dispersive X-ray spectroscopy (EDX).

Recovery of Metals from Waste Lithium Ion Battery Leachates Using Biogenic Hydrogen Sulfide

Lithium ion battery (LIB) waste is increasing globally and contains an abundance of valuable metals that can be recovered for re-use. This study aimed to evaluate the recovery of metals from LIB waste leachate using hydrogen sulfide generated by a consortium of sulfate-reducing bacteria (SRB) in a lactate-fed fluidised bed reactor (FBR). The microbial community analysis showed Desulfovibrio as the most abundant genus in a dynamic and diverse bioreactor consortium. During periods of biogenic hydrogen sulfide production, the average dissolved sulfide concentration was 507 mg L−1 and the average volumetric sulfate reduction rate was 278 mg L−1 d−1. Over 99% precipitation efficiency was achieved for Al, Ni, Co, and Cu using biogenic sulfide and NaOH, accounting for 96% of the metal value contained in the LIB waste leachate. The purity indices of the precipitates were highest for Co, being above 0.7 for the precipitate at pH 10. However, the process was not selective for individual metals due to simultaneous precipitation and the complexity of the metal content of the LIB waste. Overall, the process facilitated the production of high value mixed metal precipitates, which could be purified further or used as feedstock for other processes, such as the production of steel.

Bacterial shifts during in-situ mineralization bio-treatment to non-ferrous metal(loid) tailings

Nonferrous mine tailings have caused serious problems of co-contamination with metal(loid)s. It is still a global challenge to cost-effectively manage and mitigate the effect of the mining wastes. We conducted an in-situ bio-treatment of non-ferrous metal(loid) tailings using a microbial consortium of sulfate reducing bacteria (SRB). During the bio-treatment, the transformation of metal(loid)s (such as Cu, Fe, Mn, Pb, Sb, and Zn) into oxidizable and residual fractions in the subsurface tended to be higher than that observed in the surface. As well the mineral compositions changed becoming more complex, indicating that the sulfur reducing process of bio-treatment shaped the bio-transformation of metal(loid)s. The added SRB genera, especially Desulfotomaculum genus, colonized the tailings suggesting the coalescence of SRB consortia with indigenous communities of tailings. Such observation provides new insights for understanding the functional microbial community coalescence applied to bio-treatment. PICRUSt analysis revealed presence of genes involved in sulfate reduction, both assimilatory and dissimilatory. The potential for the utilization of both inorganic and organic sulfur compounds as S source, as well as the presence of sulfite oxidation genes indicated that SRB play an important role in the transformation of metal(loid)s. We advocate that the management of microorganisms involved in S-cycle is of paramount importance for the in situ bio-treatment of tailings, which provide new insights for the implementation of bio-treatments for mitigating the effect of tailings.

Recovery of Palladium(ii) and Platinum(ii) by Biocrystallization and Biodeposition Using a Pure Culture and Mixed Culture

Despite limited availability of platinum group metals such as palladium (Pd), there is an increasing demand to use them especially as catalysts. However, conventional recovery of these metals has proven detrimental to the environment, therefore, sustainable recycling and production is required. Biological synthesis of Pd (0) has proven to be an innovative method for recovery of palladium. This study aims to investigate the deposition of Pd at different concentrations by a pure isolate of Desulfovibrio desulfuricans and a consortium of Sulphate-reducing bacteria. The reduction was accelerated at the expanse of formate as an electron donor at a pH of 4. The results showed that after 12 hours of incubation a black precipitate of reduced Pd formed, the consortium produced a higher percentage reduction of 90% at a concentration of 2mM while the pure isolate had a percentage reduction of 77%. SEM showed electron oblique deposits on the surface of the bacteria, the deposits were between 40nm and 50nm in size. The use of the consortium proved to be highly efficient for the potential bioremediation of palladium contaminated environments.

A Comprehensive Study on Crude Methanolic Extract of Daphne gnidium L. as Effective Corrosion Inhibitors of Mild Steel Induced by SRB Consortium

The aim of the present work is the evaluation of effect of methanolic extract obtained from Daphne gnidium against biocorrosion caused by sulphate-reducing bacteria (SRB). Herein, the study of the influence of SRB consortium has been realized on the biological and electrochemical properties of the carbon steel API5LX60 immersed in water sample obtained from an Algerian oil field separator. The monitoring of the treatment effects on the SRB performance using kits test and weight loss methods showed a positive effect of the methanolic extract of D. gnidium as a corrosion inhibitor at a concentration of 0.8 g/L. In the other hand, the weight loss test has generated an efficiency rate of 95.99% at a concentration of 1.6 g/L. A linear polarization resistance approved these results, and they have given a yield of 91.14% with a polarization resistance value of 28.9 kΩ cm2 at a concentration of 0.25 g/L.

Use of carbon steel ball bearings to determine the effect of biocides and corrosion inhibitors on microbiologically influenced corrosion under flow conditions.

A consortium of sulfate-reducing bacteria consisting mostly of Desulfovibrio, Desulfomicrobium, and Desulfocurvus from oil field produced water was cultivated in a chemostat, receiving medium with 20mM formate and 10mM sulfate as the energy and 1mM acetate as the carbon source. The chemostat effluent, containing 5mM sulfide and 0.5mM of residual acetate, was passed through 1-ml syringe columns with 60 carbon steel ball bearings (BBs) of 53.6±0.1mg each at a flow rate of 0.8ml/h per column. These were treated every 5days with 1.6ml of 300ppm of glutaraldehyde (Glut), tetrakis(hydroxymethyl)phosphonium sulfate (THPS), benzalkonium chloride (BAC), or Glut/BAC, a mixture of Glut and BAC. Alternatively, BBs were treated with 33% (v/v) of a water-soluble (CR_W) or an oil-soluble (CR_O1 or CR_O3) corrosion inhibitor for 20s after which the corrosion inhibitor was drained off and BBs were packed into columns. The effluent of untreated control columns had no acetate. Treatment with the chemically reactive biocides Glut and THPS, as well as with Glut/BAC, gave a transient increase of acetate indicating decreased microbial activity. This was not seen with BAC alone indicating it to be the least effective biocide. Relative to untreated BBs (100%), those treated periodically with Glut, THPS, BAC, or Glut/BAC had a general weight loss corrosion rate of 91, 81, 45, and 36% of the untreated rate of 0.104±0.004mm/year, respectively. Single treatment with corrosion inhibitors decreased corrosion to 48, 2, and 1% of the untreated rate for CR_W, CR_O1 and CR_O3, respectively. Analysis of the distribution of corrosion rates from the weight loss of individual BBs (N = 120) indicated the presence of a more slowly and a more rapidly corroding group. BAC treatment prevented emergence of the latter, and this quaternary ammonium detergent appeared most effective in decreasing corrosion not because of its biocidal properties, but because of its corrosion inhibitory properties.

The potential impact of using a surfactant and an alcoholic co-surfactant on SRB activity during EOR

ABSTRACTSurfactants and co-surfactants play an important role in enhanced oil recovery for they improve petroleum solubility and reduce interfacial tensions between oil, water and the rock formation. Ethanol is receiving renewed attention as potential co-surfactant because of the negative results obtained with the use of salts and alkaline substances. Sulphate-reducing bacteria (SRB) can use surfactants and co-surfactants as carbon sources and, consequently, this can increase the biological accumulation of sulphide (souring). The aim of this research is to correlate SRB activity with different concentrations of co-surfactant (ethanol) as an attempt to quantifying in which concentration such compound can potentially increase or inhibit souring. The results show that the combination of surfactant (lauryl glucoside) and co-surfactant (ethanol) can increase SRB activity to about 2.3-fold. The highest sulphate consumption rate of 591 μg l−1 h−1 was observed in experiments with 0.03% and 1.5% (v/v) of surfactant and ethanol, respectively. The experiments indicated that SRB activity is only controlled by ethanol concentrations above 6.5% (v/v). Ethanol can potentially decrease costs with the use of biocides and significantly increase oil recovery ratios. Tests with the model Desulfovibrio vulgaris were not comparable with the results obtained with the SRB consortium.

PENGARUH MOLASE TERHADAP AKTIVITAS KONSORSIUM BAKTERI PEREDUKSI SULFAT DALAM MEREDUKSI SULFAT (SO4-)

The purpose of this research is to understanding the effect of organic matter on BPS activity in reducing sulfate. Research carried out in batch culture using erlenmeyer, and using a completely randomized design (CRD). The treatment given is organic matter amounted to 308 mg / L, 617 mg / L and 1.234 mg / L and control. Each treatment was repeated 3 times. The parameters observed in this study is SO4- concentration. Using Duncan New Multiple Range Test (DNMRT) at 5% level for data analysis. The results showed that the molecular concentration of 617 mg / L was able to decrease the sulfate concentration at the fastest, then consecutively the concentration of molasses 1.234 mg / L, and control. Based on the Anova test the significant value is less than 0.05. Thus it can be stated that there is an effect of addition molasses to decrease sulfate concentration by sulfate reducing bacteria consortium.

PENGARUH MOLASE TERHADAP AKTIVITAS KONSORSIUM BAKTERI PEREDUKSI SULFAT DALAM MEREDUKSI SULFAT (SO4-)

The purpose of this research is to understanding the effect of organic matter on BPS activity in reducing sulfate. Research carried out in batch culture using erlenmeyer, and using a completely randomized design (CRD). The treatment given is organic matter amounted to 308 mg / L, 617 mg / L and 1.234 mg / L and control. Each treatment was repeated 3 times. The parameters observed in this study is SO4- concentration. Using Duncan New Multiple Range Test (DNMRT) at 5% level for data analysis. The results showed that the molecular concentration of 617 mg / L was able to decrease the sulfate concentration at the fastest, then consecutively the concentration of molasses 1.234 mg / L, and control. Based on the Anova test the significant value is less than 0.05. Thus it can be stated that there is an effect of addition molasses to decrease sulfate concentration by sulfate reducing bacteria consortium.

Biological treatment of wastewater with high concentrations of zinc and sulfate ions from zinc pyrithione synthesis

Abstract An enriched and domesticated bacteria consortium of sulfate-reducing bacteria (SRB) was used to treat wastewater from zinc pyrithione (ZPT) production, and the effects of different reaction parameters on sulfate reduction and zinc precipitation were evaluated. The single-factor experimental results showed that the removal rates of Zn2+ and SO42− decreased with an increased ZPT concentration ranging from 3.0 to 5.0 mg/L. Zn2+ and SO42− in wastewater were effectively removed under the conditions of 30–35 °C, pH 7–8 and an inoculum concentration of 10%–25%. The presence of Fe0 in the SRB system enhanced Zn2+ and SO42− removal and may increase the resistance of SRB to the toxicity of Zn2+ and ZPT in wastewater. A Box–Behnken design was used to evaluate the influence of the main operating parameters on the removal rate of SO42−. The optimum parameter values were found to be pH 7.45, 33.61 °C and ZPT concentration of 0.62 mg/L, and the removal rate of SO42− reached a maximum of 91.62% under these optimum conditions.

Biological Hydrogen Sulfide and Sulfate Removal from Rubber Smoked Sheet Wastewater for Enhanced Biogas Production

The sulfate-rich wastewater from rubber smoked sheet industry could generate hydrogen sulfide (H2S) under anaerobic condition, which created bad smell to the community and might cause toxicity and damage to the environment. The H2S can be removed from the biogas by sulfur-oxidizing bacteria (SOB) with the ability to converted H2S to sulfate. Sulfate-reducing bacteria (SRB) could remove sulfate in wastewater before anaerobic treatment for biogas production. The microbial sludge from wastewater and anaerobic digestion system was collected and test for sulfate and H2S removal efficiency. Anaerobic microbial sludge has a high ability to produced methane from gelatin with a specific methane production rate of 92.4 ml CH4 gVSS-1 day-1. Anaerobic microbial sludge has lower methane production when gelatin and sulfate used as a substrate with a specific methane production rate of 81.4 ml CH4 gVSS-1 day-1. The biomethane potential, hydrogen sulfide removal and sulfate removal in anaerobic digestion system by addition of enriched cultures of SOB and SRB were investigated. The methane yield of SRB consortium was 60.1 ml CH4/gCOD with 20% sulfate reduction from wastewater and no sulfide reduction. The methane yield of SOB consortium was 41.9 ml CH4/gCOD with no sulfate and sulfide reduction from wastewater. The addition of SRB consortium could increase methane production by reducing sulfate concentration in wastewater consequently to a reduced concentration of H2S in biogas.

Sulfate-reducing bacteria stimulate gut immune responses and contribute to inflammation in experimental colitis

The intestinal microbiota is critical for mammalian immune system development and homeostasis. Sulfate-reducing bacteria (SRB) are part of the normal gut microbiota, but their increased levels may contribute to colitis development, likely in association with hydrogen sulfide (H2S) production. Here, we investigated the effects of SRB in the gut immune response in germ-free mice, and in experimental colitis. After 7days of colonization with Desulfovibrio indonesiensis or with a human SRB consortium (from patients with colitis), germ-free mice exhibited alterations in the colonic architecture, with increased cell infiltration in the lamina propria. SRB colonization upregulated the Th17 and Treg profiles of cytokine production/cell activation, in T cells from mesenteric lymph nodes. These alterations were more pronounced in mice colonized with the human SRB consortium, although D. indonesiensis colonization produced higher levels of H2S. Importantly, the colon of C57BL/6 mice with colitis induced by TNBS or oxazolone had increased SRB colonization, and the administration of D. indonesiensis to mice with TNBS-induced colitis clearly exacerbated the alterations in colonic architecture observed in the established disease, and also increased mouse weight loss. We conclude that SRB contribute to immune response activation in the gut and play an important role in colitis development.