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Abstract

In the current era, the alarming rate at which coal is being burned as a fuel is causing concern with regard to the release of sulphur oxides. According to reports, global coal consumption has increased by 0.4% in 2014. While countries like UK, Ukraine etc. have witnessed a decline in coal consumption, some others like India, China, Africa and North America have increased their use of coal to meet the energy requirements of the growing human population. The increasing use of coal has led to extensive investigations for finding an ecofriendly clean coal technology. Dibenzothiophene (DBT) and some of its alkylated derivatives present in the form of organic sulphur in coal have received a great deal of attention in the past few years because of their recalcitrant nature. Considering the economic and environmental prospects, biodesulphurization is being regarded as an effective tool for the degradation of DBT, with concomitant application towards sulphur removal from coal. Owing to the importance of microbial applications towards production of clean coal, the present review discusses some of the recent findings in the area of DBT biodegradation. In addition, current advances in coal biodesulphurization are reviewed, concluding with a consideration of future prospects for the rapidly growing energy sector.

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... Moreover, the alkylated derivatives of thiophenic compounds, seemingly, hamper the biodesulfurization process and the removal of the target element i.e., sulfur [8]. So, in order to enhance the rate of biodesulfurization process, it is needed to isolate new microbial strains having less inhibition by 2-HBP and high desulfurizing ability towards a broader range of sulfur compounds [17,22]. In our previous study [3], we described the DBT desulfurization capability and evolutionary divergence of some newly isolated bacteria and amongst them Gordonia sp. ...
... This indicated the sulfur-specific nature (cleavage of C-S bond) of Gordonia sp. HS126-4N and excluded the possibility of following the oxidative C-C bond cleavage (Kodama) and destructive C-C bond cleavage pathways [22]. Further, to confirm a sulfur-specific nature of the isolate, the ethyl acetate extract of 72 h old culture broth was analyzed by HPLC and LC/ MS for the presence of key DBT metabolites. ...
... Microbial desulfurization of fossil fuels is gaining attention due to its eco-friendly nature and low operating cost. In this regard, numerous bacteria having ability of metabolizing alkylated and non-alkylated DBTs or BTs have been reported [3,22,23]. In order to investigate the heterocyclic sulfur-containing compounds desulfurization ability of HS126-4N, we chose some typical organic sulfur compounds in fossil fuels as model compounds like DBT; 4-methyl DBT (4MDBT); 2,8-dimethyl DBT (2,8DMDBT); BT; and 3-methyl BT (3MBT). ...
Article
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Microorganisms can metabolize or transform a range of known chemical compounds present in fossil fuels by naturally having highly specific metabolic activities. In this context, the microbial desulfurization of fuels is an attractive and alternative process to the conventional hydrodesulfurization (HDS) process, since the thiophenic sulfur containing compounds such as dibenzothiophene (DBT) and benzothiophene (BT) cannot be removed by HDS. A DBT desulfurizing mesophilic bacterium, identified on the basis of 16S rRNA gene sequence as Gordonia sp. HS126-4N (source: periphery soil of a coal heap) has been evaluated for its biodesulfurization traits and potential to desulfurize the thiophenic compounds. The HPLC and LC/MS analyses of the metabolites produced from DBT desulfurization and PCR-based nucleotide sequence confirmation of the key desulfurizing genes (dszA/dszB/dszC) proved that HS126-4N could convert DBT to 2-hydroxybiphenyl (2-HBP) via the 4S pathway. The isolate could convert 0.2 mM of DBT to 2-HBP within 48 h and was reasonably tolerant against the inhibitory effect of 2-HBP (retained 70% of growth at 0.5 mM 2-HBP). The isolated biocatalyst desulfurized/degraded 100% of 0.2 mM of 4-methyl DBT, 2,8-dimethyl DBT, BT and 3-methyl BT within 108 h. The capabilities to survive and desulfurize a broad range of thiophenic sulfur containing substrates as well as less inhibition by the 2-HBP suggest that HS126-4N could be a potential candidate for improved biodesulfurization/organic sulfur removal from fossil fuels.
... In addition to the contribution of renewable energy sources, for example, wind, biomass, solar, hydro-energy etc., coal has been serving as an indispensable source of non-renewable energy since decades and finds its applications in various sectors [2][3][4]. Coal holds a major share in power generation in countries like China, U.S.A, India, South Africa, Brazil and Germany [5]. Apart from that, one of the primary utilization of coal is in the iron and steel industry, where its use has increased considerably in the last 30 years (https://www.iea.org/reports/coal-in ...
... In addition, the chemical approaches are responsible for the release of large amount of carbon dioxide into the atmosphere and also include a high operating cost. These disadvantages associated with the physicochemical techniques render the biological method as an ecofriendly approach for sulphur removal from coal [4,14]. It is to be noted that biological methods have found wide applications in treatment of several wastes offering eco-friendly and economic benefits [15][16][17]. ...
Article
Of late, sustainable energy development has received considerable importance throughout the world due to the growing concerns regarding climate change and environment protection. This in turn, has led to the search for alternatives, which are ecofriendly and cost-effective. Turkey possesses vast resources of lignite and renewable energies, which if utilized properly can reduce the current energy deficit and imports from other countries. Though renewables have received more attention in the past few years; yet, the vast lignite reserves of Turkey cannot be averted while considering the major indigenous energy resources of the country. The present review briefly discusses the existing energy situation in Turkey with particular focus on the indispensable role of coal as a valuable energy resource in meeting the country’s growing energy demand. Biodesulphurization as a green treatment technique for sulphur removal from coal is discussed along with some of the recent advances made with respect to the Turkish lignite. A brief description relating to the impact of COVID-19 on the energy sector is also discussed. Furthermore, future outlooks towards sustainable development are presented.
... Several selected bacteria are gaining momentum in bioleaching to extract metals from their respective ores in more economic and environmentally friendly way (Zeng et al. 2015;Mishra et al. 2016;Yang et al. 2016). Numerous acidophilic chemolithotrophic bacteria have been reported and characterized. ...
... In addition, the use of sulfur-oxidizing Acidithiobacillus thiooxidans along with iron-oxidizing bacteria established a remarkably effective consortium for extraction of heavy metals from their ores and industrial wastes (Baba et al. 2011;Panda et al. 2013b). Such consortia of iron-and sulfur-oxidizing acidophiles are difficult to contaminate by unwanted microorganisms that make consortia industrially important for novel applications in many sectors (Mishra et al. 2016;Zhu et al. 2011). Bioleaching studies of several minerals have exhibited satisfactory recovery of metals using acidophilic bacteria. ...
Article
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Indigenous iron-oxidizing bacteria were isolated on modified selective 9KFe2+ medium from Baiyin copper mine stope, China. Three distinct acidophilic bacteria were isolated and identified by analyzing the sequences of 16S rRNA gene. Based on published sequences of 16S rRNA gene in the GenBank, a phylogenetic tree was constructed. The sequence of isolate WG101 showed 99% homology with Acidithiobacillus ferrooxidans strain AS2. Isolate WG102 exhibited 98% similarity with Leptospirillum ferriphilum strain YSK. Similarly, isolate WG103 showed 98% similarity with Leptospirillum ferrooxidans strain L15. Furthermore, the biotechnological potential of these isolates in consortia form was evaluated to recover copper and zinc from their ore. Under optimized conditions, 77.68 ± 3.55% of copper and 70.58 ± 3.77% of zinc were dissolved. During the bioleaching process, analytical study of pH and oxidation-reduction potential fluctuations were monitored that reflected efficient activity of the bacterial consortia. The FTIR analysis confirmed the variation in bands after treatment with consortia. The impact of consortia on iron speciation within bioleached ore was analyzed using Mössbauer spectroscopy and clear changes in iron speciation was reported. The use of indigenous bacterial consortia is more efficient compared to pure inoculum. This study provided the basic essential conditions for further upscaling bioleaching application for metal extraction.
... Owing to its high toxicity, inhalation of DBT causes lung disorders in human beings and causes inflammation if it comes in direct contact with the skin. Apart from its effects on human beings, it can also have harmful effects on aquatic life (Mishra et al., 2016). ...
... Desulphurization of Kuwait crude oil was also carried out using Desulfovibrio desulphuricans M6, which resulted in 21% of sulphur reduction along with the release of H2S (Kim et al., 1990). Armstrong et al. (1995) Nevertheless, the anaerobic biodesulphurization process proceeds at a very slow pace, specifically when the reactants consist of organic compounds, as DBT, where only 10% of the energy generated as a result of substrate utilization is employed for microbial growth, while 50% under aerobic conditions (Mishra et al., 2016). Further research should be performed to implement anaerobic biodesulfuration because under the aerobic route is difficult to remove the final end product i.e. sulphate formed during the reaction, while H2S formed in the anaerobic route can be easily treated in the desulphurization plants. ...
Thesis
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Summary Microbial electrochemistry is an emerging biotechnological discipline based on the interactions between microorganisms and electrically conductive materials. All the assorted technologies based on this principle are referred as “Microbial Electrochemical Technologies” (METs) and their range of applications spans diverse fields. For instance, a system based on Microbial Electrochemistry conforms a novel strategy for enhancing the clean-up of polluted environments. The novelty of this application consists in the unlimited character of electrodes as terminal electron acceptor (anode) or donors (cathode), unchaining microbial metabolism activities beyond the natural conditions. The versatility of these systems allows the application of electrode-assisted bioremediation in matrices as different as wastewater, sediment, soil and manure. Nevertheless, overcoming microbial, technological and economical challenges is basic for the implementation of such a system in real-field applications. In this thesis, we have conformed new redox scenarios supplied by electrodes for degrading 3 different pollutants in 3 different matrices, using the electrode as a terminal electron acceptor: dibenzothiophene (polycyclic aromatic hydrocarbon) in paddy soil, isoproturon (herbicide) in agricultural soil and sulfamethazine (antibiotic) in manure. The work has been organized in 5 chapters, 3 of them being experimental. Chapter 1 establishes an introduction to microbial electrochemistry, its fundamentals and its applications. We centre the attention in the state of the art of Microbial Electrochemical Systems as bioremediation tools of polluted environments. Conventional bioremediation techniques have acted by supplying nutrients, co-metabolites, oxygen or other electron donors or acceptors (biostimulation) or by adding additional microorganisms able to degrade a specific pollutant (bioaugmentation). Electrode-assisted bioremediation means a novel strategy to stimulate microbial activity, avoiding the supply of costly chemical amendments that diffuse uncontrollably and might be consumed in unwanted metabolic reactions. Furthermore, electrodes not only overcome the deficiency of suitable electron donors or acceptors in highly reductive environments, but also provide a battery of tailored redox scenarios that can be displayed and interchanged in reference to the different pollutant chemical nature, redox conditions and matrix. Additionally, the introduction presents the pollutants tested in this thesis, their ecological impact and their degradation current knowledge. One common feature of the compounds evaluated is the scarce research about their biodegradation under flooded and extreme reductive conditions. The common feature of the matrices is their high resistivity that restrains the transport of ions between electrodes, and makes them less favourable scenarios for electrode-assisted bioremediation. All the objectives aimed in this thesis are also outlined also in Chapter 1. In Chapter 2 we establish the term Microbial Electroremediating Cell (MERCs) to refer to METs that in spite of harvesting energy, aim to maximize metabolic oxidation or reduction for enhancing the biodegradation of a pollutant. MERCs outperform the removal of dibenzothiophene (DBT) compared to the natural attenuation under flooded conditions. Moreover, the study was complemented with toxicological analyses for verifying a real clean-up of DBT-polluted soil. Green algae confirm a toxicity decrease of the treated soil during incubation in MERCs, in contrast to the unaltered values detected under natural conditions. Our results also reveal that the mere presence of conductive material enhanced the biodegradation of DBT, which raises this conductive material-assisted bioremediation as a very promising technique to treat polluted environments. The flexibility of these systems for operating under different electrode configurations or redox conditions makes this technology a very versatile tool for cleaning up with pollutants of different nature. So the first part of Chapter 3 demonstrates that isoproturon (IPU) total degradation to CO2 can be enhanced by polarizing the anode at positive potentials. In this case the 14C detection techniques provide a precise measurement of the stimulation capacity of electrodes to degrade IPU. We introduce the term bioelectroventing to designate the process to supply electrodes to stimulate the oxidative metabolism of environmental microbial populations in allusion to the similarities with the traditional bioremediation technique bioventing, where oxygen is artificially applied as electron acceptor. This chapter also reports an overall profile of the 14C-IPU metabolites and 14C mass balance in response to the different treatments. In the second part of Chapter 3, we demonstrate how the use of electrodes at high anodic potential (+600 mV versus Ag/AgCl) in IPU-contaminated soil increases not only the IPU-removal, but also leads to effective clean-up demonstrated by ecotoxicological analysis of treated soils. Furthermore, electrode potential differences induced taxonomical shifts in the microbial community. So thus, microbial metabolism and community structure respond to the bioelectrochemically stimulation, linking functional differences (IPU-removal) with taxonomical microbial shifts. We also use the microbial community profile as a reporter of the electrode influence, suggesting that the electrode effect to change the communities profile is at least 0.5 cm. As a final scientific contribution, Chapter 4 explores the operation of MERCs in flooded manure to degrade sulfamethazine (SMZ). This compound is frequently used in veterinary medicine and enters the environment by using manure as soil fertilizer due to its incomplete absorption in the animal gut and its unmetabolized excretion. Our results have revealed how the use of electrodes at negative anodic potential (-400 mV versus Ag/AgCl) in SMZ-contaminated manure increases, not only the SMZ-removal, but also influence the compound fate. Similarly than in the study with DBT in polluted soils, our results also reveal that the mere presence of conductive material enhanced the mineralization to 14CO2 of the radiolabeled antibiotic. We hypothesized that conducted material acts as assistance of a process called Direct Interspecies Electron Transfer (DIET), a metabolism that consists in interchanging electrons in the absence of electron shuttles or redox mediators, just through direct electrical connections between microbes. Finally, in Chapter 5 we introduce a general discussion, conclusions and future work based on our experimental results. The general discussion is presented under a question-answer mode. The remarkable impact of electrodes on bioremediation of polluted environments suggests a promising future for this emerging environmental technology as a potential alternative to conventional bioremediating techniques, enforcing the establishment of electrodes as a conceivable cost-effective and environmentally friendly strategy for enhancing pollutants degradation under extreme reductive conditions.
... At the same time retaining restricted sulfur emission as per the stringent rules for pollution control, the need of appropriate desulfurizing technologies for high sulfur-containing fossil fuels has become a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 crucial. Among various sulfur bearing compounds the most predominant form of sulfur is dibenzothiophene (DBT) and its derivatives in the petroleum and coal [4,5] which is refractory to the contemporary desulfurization techniques. ...
... Different intermediate and end products warrants for the divergent evolution of dsz genes by strains isolated from different sources. To test our hypothesis we further investigated MTCC strains which were able to desulfurize free-DBT for the BDS of Assam coal which has high organic sulfur [5]. In support of our hypothesis, we could not get any significant desulfurization by these strains (Data not shown). ...
Article
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Since the sulfur specific cleavage is vital for the organic sulfur removal from fossil fuel, we explored potential bacterial strains of MTCC (Microbial Type Culture Collection) to desulfurize the Dibenzothiophene (DBT) through C-S bond cleavage (4-S pathway). MTCC strains Rhodococcus rhodochrous (3552), Arthrobacter sulfureus (3332), Gordonia rubropertincta (289), and Rhodococcus erythropolis (3951) capable of growing in 0.5 mM DBT were examined for their desulfurization ability. The presence of dsz genes as well as the metabolites was screened by polymerase chain reaction (PCR) and HPLC, respectively. All these strains showed > 99% DBT desulfurization with 10 days of incubation in minimal salt medium. From the HPLC analysis it was further revealed that these MTCC strains show differences in the end metabolites and desulfurize DBT differently following a variation in the regular 4-S pathway. These findings are also well corroborating with their respective organization of dszABC operons and their relative abundance. The above MTCC strains are capable of desulfurizing DBT efficiently and hence can be explored for biodesulfurization of petrochemicals and coal with an eco-friendly and energy economical process.
... Coal can be used in many industries, including the steel, cement, building, coal power, coke, coal chemistry, and paper and textile industries, etc. [18,20] . Most of these industries need the heat from coal combustion. ...
... There are two zones in this concept: one is to remove moisture in coal with a temperature of approximately 149 °C, and the other is a hazardous air pollutants (HAPs) zone, which aims to remove the mercury with a temperature of about 288 °C. The volatilized mercury will be collected and 20. The mild pyrolysis concept for mercury removal from coal [268] . ...
Article
Mercury, as a global pollutant, has raised worldwide concern due to its high toxicity, long-distance transport, persistence, and bioaccumulation in the environment. Coal-fired power plants (CFPPs) are considered as the major anthropogenic mercury emission source to the atmosphere, especially for China, India, and the US. Studies on mercury in coal combustion process have been carried out for decades, which include content and occurrence forms of mercury in coal, mercury transformation during coal combustion, sampling, co-removal and emission of mercury in CFPPs, mercury removal technologies for CFPPs. This current review summarizes the knowledge and research developments concerning these mercury-related issues, and hopes to provide a comprehensive understanding of mercury in coal combustion process and guidance for future mercury research directions. The average mercury content in the coal from China, the US, and South Africa is 0.20, 0.17, and 0.20 mg/kg, respectively, which is higher than the world's coal average value of 0.1 mg/kg. In general, mercury in coal is in the forms of sulfide-bound mercury (mainly pyritic mercury, dominant), clay-bound mercury, and organic matter-bound mercury, which are influenced by diagenetic, coalification, and post-diagenetic conditions, etc. Mercury transformation in coal combustion includes homogeneous (without fly ash) and heterogeneous (with fly ash) reaction. The transformation is affected by the coal types, flue gas components, flue gas temperature, combustion atmosphere, coal ash properties, etc. The effects of chlorine, NOx, SO2, H2O, O2 NH3 on elemental mercury (Hg⁰) homogeneous oxidation and the influence of physical structure properties, unburned carbon, and metal oxides in fly ash as well as flue gas components on Hg⁰ heterogeneous transformation are systematically reviewed in detail. For the mercury transformation in oxy-coal combustion, O2 promotes Hg⁰ oxidation with Cl2 while NO and CO2 inhibit or do not favor that reaction. CO2 increases Hg⁰ oxidation in the atmosphere of NO and N2. SO2 will limit Hg⁰ oxidation, while HCl has a higher oxidation effect on Hg⁰ than that in air-coal combustion atmosphere. Fly ash plays an important role in Hg⁰ oxidation. SO3 inhibits mercury retention by fly ash while H2O promotes the oxidation. The sampling or analysis principle, sampling requirements, and advantages and disadvantages of the commonly used on-site mercury sampling methods, namely, Ontarion Hydro Method (OHM), US EPA Method 30B, and Hg-CEMS, are compared. The air pollution control devices (APCDs) in CFPPs also have the mercury co-removal ability besides the conventional pollutants, such as NOx, particulate matter (PM), SO2, and fine PM. Selective catalytic reduction (SCR) equipment, electrostatic precipitator (ESP) or fabric filter (FF), and wet flue gas desulfurization (WFGD) device are good at Hg⁰ oxidation, particulate mercury (Hgp) removal, and oxidized mercury (Hg²⁺) capture, respectively. The Hg⁰ oxidation rate for SCR equipment, and the total mercury (Hgt, Hgt = Hg⁰ + Hg²⁺ + Hgp) removal rate for ESP, FF, and WFGD device is 6.5–79.9%, 11.5–90.4%, 28.5–90%, and 3.9–72%, respectively. Wet electrostatic precipitator (WESP) can capture Hg⁰, Hg²⁺, and Hgp simultaneously. The mercury transformation process in SCR, ESP, FF, WFGD, and WESP is also discussed. Hgt removal in ESP+WFGD, SCR+ESP+WFGD, SCR+ESP+FF+WFGD, and SCR+ESP+WFGD+WESP is 35.5–84%, 43.8–94.9%, 58.78–73.32%, and 56.59–89.07%, respectively. The mercury emission concentration in the reviewed CFPPs of China, South Korea, Poland, the Netherlands, and the US is 0.29–16.3 µg/m³. Mercury in some fly ash and gypsum, and in most WFGD and WESP wastewater, is higher than the relevant limits, which needs to be paid attention to during their processing. Mercury removal technologies for CFPPs can be divided into pre-combustion (including coal washing technology and mild pyrolysis method), in-combustion (including low-NOx combustion technology, circulating fluidized bed combustion technology, and halogens addition into coal), and post-combustion (including existing commercial SCR catalyst improvement, inhibiting Hg⁰ re-emission in WFGD, mercury oxidizing catalysts, injecting oxidizing chemicals, carbon-based adsorbents, fly ash, calcium-based adsorbents, and mineral adsorbents) based on the mercury removal position. The mercury removal effects, mercury removal mechanism, and/or influencing factors are summarized in detail. One of the regenerable mercury removal adsorbents, the magnetic adsorbent modified by metal oxides or the metal halides, is the most promising sorbent for mercury removal from CFPPs. It has advantages of high mercury removal efficiency, low investment, easy separation from fly ash, and mercury recovery, etc. Lastly, further works about mercury transformation in coal combustion atmosphere, mercury co-removal by APCDs, the emission in CFPPs, and mercury removal technologies for CFPPs are noted.
... Carbon dioxide has been identified as a primary contributor to global warming. The following impact of coal burning was reported by Ref. [129].1) Naturally occurring radionuclides present in soils are same as coal samples. ...
... However, coal-based plants are considered to be higher health risk to the population if the entire emitted gaseous and particulate are considered [130]. It was recommended by Ref. [129] that the radiation dose from thermal power plants can be reduced by reducing the ash content of coal. Number of technologies and processes can be exploited to alleviate negative environmental impacts. ...
Article
Full-text available
As Bangladesh's economy expands, the country has experienced severe power crises over the decades. With the Government's effective implementation of policies, the country has shown remarkable progress in energy sector recently. Even though various initiatives have been undertaken to improve energy sector, thevision of power sector hasn't yet achieved. To accelerate the progress in energy sector, the country needs to reform the transmission and distribution sector of the country to reduce the distribution losses. The effort should be given to the fuel demand and supply side management, energy efficiency and diversifying program for sustainable development in energy sector. Thus, revisiting the existing reform process in the energy sector is needed to be investigated to meet ever rising energy demand. The paper assesses the major regulatory framework changes commenced by the government in power sector and identifies key issues that led to the passage of the affordable and sustainable energy for all. In addition, fuzzy rule-based GHG emission predicting system is designed in this research which demonstrates how the GHG emission varies with the variables i.e., renewable integration, fossil fuel management, fossil fuel quality and use of modern technology and suggests the effective and efficient GHG emission reduction process from power generating sector. Finally, policy perspective, control and co-ordination issues in energy sector were discussed.
... The generation of fly ash (FA) resulting out of coal burning is being increased up to a considerable extent owing to the extensive rate of usages of coal in thermal power sectors Mishra et al., 2018;Mishra et al., 2016). This leads to cause serious concerns in the environment in the context of the management of the large quantity of the FA generated, and hence, it urges to develop suitable technology for its safe environmental disposal (Dan et al. 2021). ...
Article
The present investigation is intended to develop the stabilization and transportation behavior of fly ash slurry (FAS) using the mixture of the surfactants, namely, Sapindus laurifolia (S. laurifolia, natural) and sodium dodecyl sulfate (SDS, synthetic). In addition to the rheological study, an attempt has been made to remove the toxic and other trace metals through the leaching method to address the safe disposal of FAS for mining backfilling applications. The data obtained from the different rheological studies of ash concentrations in the range of 45–65.8% were fitted to the Bingham plastic model. Addition of synthetic surfactant SDS to natural surfactant S. Laurifolia does enhance the wettability of fly ash (FA) particles by decreasing the surface tension and increasing the zeta potential of the slurry. The effect of other parameters like temperature, mixed surfactant concentration, and FA concentration on the formulation, stability, and leachability of FAS was investigated and reported. The results from the present investigation revealed that the optimum dosages of surfactants for both leaching and transportation of FAS is 0.009 g/cc of saponin and 0.008 g/cc of SDS. The stabilization interaction and leaching mechanism were proposed considering the hydrophobic/hydrophilic property of FA, S. laurifolia, and SDS. Abbreviations CMC: Critical micellar concentration; S. laurifolia: Sapindus laurifolia; SDS: Sodium dodecyl sulfate; FA: Fly ash; FAS: Fly ash slurry; η: Dynamic viscosity; τ0: Yield stress; γ: Applied shear rate; ζ: Zeta potential; τ: Shear stress
... The illustration in Figure 7 placed the bacteria members in the 4S pathway based on their activities and growth turnover in coal medium (Figures 1-6) and some references. The 4S is a well-known biodegradation pathway of dibenzothiophene (Jatoi et al., 2021;Li et al., 2019;Martín-Cabello et al., 2020;Mishra et al., 2016;Sousa et al., 2020). The most dominant role member in the coal consortium is M. osloensis COK1. ...
Article
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Efforts to reduce organic sulfur in coal are taken through biodesulfurization by using desulfurization bacteria to release covalently-bound sulfur from the coal matrix. Coal is a complex hydrocarbon material that requires collaboration from more than one type of bacteria in a consortium for desulfurization. The current study shows how the individual members of a bacterial consortium obtained directly from coal samples grew on the coal. Mineral medium containing sub-bituminous coal with a concentration of 10%, 15%, and 20% served as a carbon source and the only sulfur to support the consortium's growth. The examination included growth patterns, concentrations of dibenzothiophene as an organic sulfur representative, pH, and sulfate concentration as the sulfur product released into the medium. The growth of individual members of the consortium was observed for 336 h. The consortium grew in all three coal concentrations with slightly different cell growth patterns and the release of dibenzothiophene. Members of the consortium grew alternately and overlapped, which showed possible linkages or dependence on products and existence from the growth of other members. The existence of the primary strain Moraxella osloensis COK1 indicated that they played a role in the activities and growth of other members. The alternating growth is discussed to produce a hypothetical illustration of how several other members play in using sulfur in a well-known desulfurization pathway. In conclusion, this study provides a deeper insight into the value of consortium members individually but growing together while swarming coal as a complex resource to become low-sulfur coal.
... Interestingly, they are also not usually subjected to other microbial contamination. Such unique features make these microbes industrially important there by finding novel applications [14][15][16]. ...
Article
Simultaneous multi-metal leaching from industrial pyrite ash is reported for the first time using a novel bioreactor system that allows natural diffusion of atmospheric O2 and CO2 along with the required temperature maintenance. The waste containing economically important metals (Cu, Co, Zn & As) was leached using an adapted consortium of meso-acidophilic Fe(2+) and S oxidising bacteria. The unique property of the sample supported adequate growth and activity of the acidophiles, thereby, driving the (bio) chemical reactions. Oxido-reductive potentials were seen to improve with time and the system's pH lowered as a result of active S oxidation. Increase in sulphur dosage (>1g/L) and agitation speed (>150rpm) did not bear any significant effect on metal dissolution. The consortium was able to leach 94.01% Cu (11.75% dissolution/d), 98.54% Co (12.3% dissolution/d), 75.95% Zn (9.49% dissolution/d) and 60.80% As (7.6% dissolution/d) at 150rpm, 1g/L sulphur, 30°C in 8days.
... Sulfur oxide (SO x ) emission from the burning of the sulfur loaded fossil fuels causes serious health (bronchial irritation and asthma), environmental (acidic rains), as well as technical problems (corrosion of the machinery) [15,17]. The process of hydrodesulfurization (HDS) is being used to remove sulfur; however, HDS demands severe operational conditions and cannot remove sulfur from thiophenic compounds such as dibenzothiophene (DBT), benzothiophene (BT), and their alkylated forms [8,18,20]. ...
Article
Full-text available
Rhodococcus sp. Eu-32 has shown an extended novel dibenzothiophene desulfurization sulfur-specific 4S pathway and could remove significant amounts of organic sulfur from coal. Here, we present the draft genome sequence of Eu-32 with a genome size of approximately 5.61 Mb, containing 5065 protein coding sequences with a G+C content of 65.1%. The Rhodococcus sp. Eu-32 showed ~ 99% identity at the 16S rRNA gene sequence level while < 34% digital DNA–DNA hybridization and < 81% average nucleotide identity values with the genome sequence of most closely related known Rhodococcus species, suggesting that it is taxonomically different from the already reported Rhodococcus species. Among the annotated genes, 90 are involved in the metabolism of sulfur. Comparative genome analysis suggests many commonalities in sulfur metabolism gene sets that may have evolved due to many factors including ecological pressures. Our study and the genome sequence data will be available for further research and will provide insights into potential biotechnological and industrial applications of this bacterium.
... In addition, certain acidophilic strains such as Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans have also been used for the biodesulphurization of Cayirhan lignites, which resulted in a maximum sulphur removal of 78.2% (Gürü et al., 2006). In general, biodesulphurization of coal has also been reported using several bacterial and fungal strains such as Sinomonas flava XL4, Sulpholobus acidocaldarius, Sulpholobus brierleyi, Pseudomonas aeruginosa, Pseudomonas putida, Beggiatoa, Rhodococcus sp., Fusarium oxysporum, Aspergilllus niger and Exophiala spinifera (Etemadzadeh et al., 2016;Liu et al., 2015;Mishra et al., 2016Mishra et al., , 2017. ...
Article
Coal has been serving as a profuse source of energy since centuries and several attempts are being made to reduce sulphur emission levels from coal. Recently, pretreatment techniques such as ultrasonication and utilization of surfactants as additives have surfaced aiming at improving the biodesulphurization of coal. In the present study, biodesulphurization of Turkish lignite was studied for the first time using Leptospirillum ferriphilum. Attempts have been made to study the biodesulphurization aspects of the lignite sample where the effect of Fe²⁺ iron, surfactant Span 80 and ultrasonication were studied under shake flask conditions. The study indicated Fe²⁺ to be an essential component in the growth media for improving biodesulphurization performance (with 56.2% total sulphur removal). Span 80 (0.05% v/v) marginally enhanced the biodesulphurization of the lignite sample (nearly 61% of total sulphur removal). The carbon content in the lignite sample increased following biodesulphurization. Ultrasonication of the lignite sample, on the other hand, did not yield significant sulphur removal when compared to the effect of Span 80. About 57.6% of total sulphur could be removed from the sample when ultrasonicated for 60 min. Mineralogical characterization along with thermal analysis of the samples pre and post biodesulphurization provided more information on different phases present in coal and the effect of microbial treatment on them.
... For the scale-up studies, mostly stirred tank reactors and airlift reactors have been used. 15 Apart from that, Cara et al. 16 have reported the packed column leaching of a 5 kg coal sample using a mixed culture of acidophilic strains, where they achieved a maximum sulfur removal of 24% in 125 days. Besides, a pilot scale study (in a 525 L batch bioreactor) has been carried out with Tabas coal using Acidithiobacillus ferrooxidans, where a maximum sulfur removal of 20% was achieved in 14 days, out of which 45% comprised pyritic sulfur. ...
Article
The low rank coal lignite stands out to be a profuse source of energy in Turkey and accounts for nearly 43% of its total fossil fuel production. However, the high sulfur content associated with lignite averts its application in several sectors due to various health and environmental issues. In the present work, biodesulphurization of Turkish lignite was studied in 1 and 20 L aerated bioreactors using an iron oxidizing acidophile, Leptospirillum ferriphilum (L. ferriphilum). Additionally, the effect of Span 80 (S80) on biodesulphurization of the sample was studied, under the optimum concentration derived from our previous shake flask study, in order to notice its effect under scale-up aerated bioreactor conditions. Under lab scale (using 1 L bioreactors), in the absence of S80, L. ferriphilum could desulphurize a maximum of 65.6% sulfur from the lignite sample, while 56% desulphurization was achieved in the presence of 0.05% (v/v) S80. Further scale-up studies under semipilot conditions (in 20 L reactors) indicated a maximum desulphurization of 63% from the sample in absence of S80. The pH, oxidation–reduction potential (ORP), and Fe2+ iron and total iron concentrations were periodically monitored in all the reactors during the course of the experiments. XRD and FTIR characterization of the lignite samples pre and post biodesulphurization provided valuable information on the structural and phase changes due to the microbial action.
... In addition, Leptospirillum ferrooxidans along with Acidithiobacillus thiooxidans constitute a remarkably important consortium for leaching of heavy metals from various mining and industrial wastes [17,18]. These iron and/or sulphur oxidizing acidophiles are hardly contaminated with unwanted microbes which make them industrially important thereby finding novel applications in several sectors [9,19,20]. Owing to the importance of these industrially important microbes, the present study evaluates the biotechnological potential of such microbes to simultaneously recover metal values from pyrite ash waste of the Turkish acid production plant. Several physicochemical and biological process parameters have been optimized and suitable conditions have been established for a scale-up study. ...
Article
Pyrite ash, a waste by-product formed during roasting of pyrite ores, is a good source of valuable metals. The waste is associated with several environmental issues due to its dumping in sea and/or land filling. Although several other management practices are available for its utilization, the waste still awaits and calls for an eco-friendly biotechnological application for metal recovery. In the present study, chemolithotrophic meso-acidophilic iron and sulphur oxidisers were evaluated for the first time towards simultaneous mutli-metal recovery from pyrite ash. XRD and XRF analysis indicated higher amount of Hematite (Fe2O3) in the sample. ICP–OES analysis indicated concentrations of Cu > Zn > Co> As that were considered for bioleaching. Optimization studies indicated Cu −95%, Co −97%, Zn − 78% and As −60% recovery within 8 days at 10% pulp density, pH −1.75, 10% (v/v) inoculum and 9 g/L Fe²⁺. The productivity of the bioleaching system was found to be Cu −1696 ppm/d (12% dissolution/d), Co −338 ppm/d (12.2% dissolution/d), Zn −576 ppm/d (9.8% dissolution/d) and As −75 ppm/d (7.5% dissolution/d). Synergistic actions for Fe²⁺ −S° oxidation by iron and sulphur oxidisers were identified as the key drivers for enhanced metal dissolution from pyrite ash sample.
... Acid rain is detrimental to the life of animals, plants, ecosystem, and entire environment (Hu et al. 2018;Makgato and Chirwa 2020). DBT is highly toxic to human lungs and inflames the skin (Mishra et al. 2016) and also causes chronic respiratory illnesses. Sulfate aerosols cause corrosion, abrasion, fouling and slagging of metals and leads to leakage in the boiler tubes (Mketo et al. 2016;Makgato and Chirwa 2020). ...
... Among these methods, physical method is cost-effective and can remove a part of pyritic sulfur, but cannot reduce organic sulfur (Zhao et al., 2008). Both organic and inorganic sulfur from coal can be effectively removed by chemical method, but chemical method needs high temperature and pressure (Soleimani et al., 2007;Xia, 2018) associated with high operating cost (Mishra et al., 2016) and loss of partial combustible matters (Cara et al., 2006). Furthermore, the chemical method releases large amounts of CO 2 and also secondary hazardous products. ...
Article
Coal is the most abundant fossil fuel in the world and its combustion accompanies with the emission of SOX, which is responsible for serious environmental problems. To reduce the emission of SOX is essential for clean fuel. In the present study, indigenous microorganisms acclimatized from fat coal itself and exotic microorganisms from sewage sludge were used for coal biodesulfurization. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and Raman spectral analysis were used to investigate the structural change of fat coal during the bioleaching. Results showed that kaolinite and quartz were the main minerals, and pyrite was the main inorganic sulfide in fat coal. After 36-day biodesulfurization, the total sulfur in fat coal decreased from 5.07% to 2.77% and 2.75%, and the pyritic removal was 77.68% and 87.88% with indigenous and exotic microorganisms, respectively. The exotic microorganisms were more effective to oxidize the pyrite than the indigenous microorganisms. But both microorganisms did not interact with the organic sulfur, which existed as C–S bond in fat coal. FT-IR analyses showed the damage of kaolinite structure, indicating potential microbial effect on kaolinite, which has not been reported before. Raman spectral analysis was for the first time used to investigate the changes of coal macromolecular structure during the bioleaching. FT-IR and Raman spectra confirmed the changes of aromatic C–H, O–H bonds, which led to the increase of carbon crystallinity index.
... The most common compound for sulfur degradation is dibenzothiophene (DBT; Das and Chandran, 2011). DBT has gained global attention due to its removal of organic sulfur (Mishra et al., 2016). Certain bacteria may degrade sulfur in complex organic sulfur compounds (such as DBT) for their growth and essential processes and thus can be used to remove organic sulfur from fossil fuels. ...
Article
Full-text available
Sulfur, organosulfur compounds, and sulfides are essential parts of life. Microbial sulfate assimilation is among the most active and ancient metabolic activities in the sulfur cycle that operates in various ecosystems. We analyzed the molecular basis of bacterial characterization. NR1 was isolated and purified from mangrove sediments. Whole-genome sequencing indicated that the NR1 isolate was closely related to Bacillus cereus. The genome contained 5,305 functional genes with a total length of 5,420,664 bp, a GC content of 35.62%, 42 rRNA, and 107 tRNA. DBT-grown cultures exhibited DBT utilization, fleeting emergence of DBT sulfone (DBTO2), and formation of 2-hydroxybiphenyl (2-HBP). Molecular analysis of the PCR products’ dsz operon revealed the presence of dszA, dszB, and dszC genes, which encoded for NR1’s 90% DBT desulfurization activity. Furthermore, 17 sulfur metabolism-related genes, including genes involved in assimilation sulfate reduction, APS and PAPS, and the cys, ssu, and TST gene families, were identified. In sulfate media, alkenesulfonate was converted to sulfite and inhibited ssu enzymes. Downregulated cysK variants were associated with nrnA expression and the regulation of L-cysteine synthesis. These findings established a scientific foundation for further research and application of bacteria to mangrove rehabilitation and ecological treatment by evaluating the bacterial characterization and sulfur degradation metabolic pathway. We used whole-genome and transcriptome sequencing to examine their genetic characteristics.
... This became possible due to the screening of higher numbers of environments for such microorganisms and new techniques were used for the screening of these microorganisms capable of bioleaching [9,10]. Several selected bacteria are gaining momentum in bioleaching to extract metals from their respective ores in more economical and eco-friendly way [15][16][17]. Numerous acidophilic chemolithotrophic bacteria have been reported and characterized. ...
Article
The exploration of microbial diversity in extremely acidic habitats has provided a vital base for the progression of minerals biotechnology. Three indigenous iron‐oxidizing acidophilic bacterial strains were isolated through serial dilution of enriched bacterial culture from Baiyin Copper Mine Stope, China. The morphological, biochemical, physiological, and phylogenetic characteristics of isolates were investigated. These isolates were motile, Gram‐negative, and curved shape with pleomorphism except isolate WG101 that was a straight rod. The optimum growth pH and temperature for all isolates were 1.5 and 30 °C, respectively, and showed extreme acidophilic nature. All the isolates showed obligate chemoautotrophic nature and used ferrous iron and pyrite as an energy source, however, isolates WG102 and WG103 were unable to use sulfur, while isolate WG101 could use elemental sulfur and reduced inorganic sodium thiosulfate as an energy source. The phylogenetic analyses based on 16S rRNA sequences revealed that the isolates WG101, WG102, and WG103 were homologous with Acidithiobacillus ferrooxidans strain AS2 (99%), Leptospirillum ferriphilum strain YSK (98%), and Leptospirillum ferrooxidans strain L15 (98%), respectively. These bacterial isolates showed efficient copper and zinc dissolution from the ore. The metals dissolution rate of At. ferrooxidans strain WG101 was 54.5 ± 4.33% (copper) and 49.6 ± 5% (zinc). The metals recovery rate of L. ferriphilum strain WG102 was 45.7 ± 3.5% (copper) and 40.5 ± 2.5% (zinc). The recovery rate of copper and zinc was 49.6 ± 4% and 46.5 ± 3% respectively in the case of L. ferrooxidans strain WG103. The findings of this study are consistent with the notion that the indigenous bacteria are more efficient in minerals dissolution.
... Biodesulfurization (BDS) emerged as an environmentally friendly technology able to reduce contamination from fossil fuels, under mild pressures and temperatures [1]. Despite numerous studies of this methodology [2][3][4][5][6], the process still presents several unresolved difficulties, among them the high cost of biocatalysis, reactor design, separation of aqueous-organic phases and biocatalytic stability and lifetime [7,8]. However, the main disadvantage of BDS process is the limited access of the microorganisms to the organic substrates, due to the low bioavailability of sulfur compounds in the bacterial aqueous medium [9]. ...
Article
Full-text available
Experimental biodesulfurization (BDS) data for dibenzothiophene (DBT) (1.0-7.0 mM) with Rhodococcus rhodochorus immobilized by adsorption on silica, were adjusted with liquid-film kinetic model (Fisher coefficient, F = 592.74 and probability value p << 0.05 and r² = 0.97). Simulations predict the presence of considerable amounts of DBT surrounding the particles, which would be available for the cells adsorbed on the surface of silica. The greatest percentage removal (50 %) was obtained for adsorbed cell system over the suspended bacterial cells (30 %), showing that sulfur substrates are more bioavailable when the bacterial cells are adsorbed on silica. The liquid-film modelling with diffusional effects provides proper theoretical basis to explain the BDS performance obtained using adsorbed cells.
... DBT is highly toxic and its inhalation leads to lung disorders in human and causes inflammation if it comes in contact with skin (Mishra et al. 2016). During its refining, more amount of sulphur oxides may lead to the acid rain, pollute the environment, biosphere and may cause other health issues (Tailleur et al. 2005 andOllivier 2005). ...
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Bacterial strains are successfully employed to desulfurize dibenzothiophene which may be determined by chromatography, HPLC and GC-Mass spectrometry. Strains of Ralstonia sp ., Pseudoxanthomons sp. and Rhodococcus sp. were used in the present investigation. Only Rhodococcus sp. was able to convert dibenzothiophene (DBT) into 2-hydroxy biphenyl (2-HBP). Gibb’s assay blue colour indicates the conversion of DBT into 2-HBP and brown colour indicates complete consumption of DBT by bacteria. After two days of bacterial treatment, there was no further removal of DBT. Conversion of DBT into 2-HBP was monitored through HPLC for six days of entire experiment.
... It is important to note that Acidithiobacillus ferrooxidans, an iron and sulfuroxidizing microbe belonging to the c-proteobacteria group, is the well studied microorganism ( [35] and references therein). Acidithiobacillus ferrooxidans along with Leptospirillum ferrooxidans and Acidithiobacillus thiooxidans constitute a remarkably important consortium for metal sulfide oxidation and in particular finds a number of applications for bioleaching of metals, biodesulfurization of coal, etc., [3,[31][32][33][36][37][38][39][40][41]. The chemical activity of biogenic Fe ?3 also contribute towards acid generation. ...
Article
Acid mine drainage (AMD) is recognised as a serious and global environmental problem. The major producer of these toxic effluents is the mining industry. Owing to the severe effects of these effluents, their prevention and treatment have been a primary focus of research over several decades. The problems have invited the attention of a large group of researchers, governmental bodies, educational and research establishments, mining industries, general public and environmental specialists. A preferable option is to prevent the formation and movement of AMD from its source of origin; however, it is not possible in many locations. It, therefore, becomes essential to collect and treat AMD to which a number of treatment techniques are available. Despite the extreme environmental conditions, several communities of autotrophic and heterotrophic bacteria and archaea are seen to flourish that mainly drive the rate of release of sulfur and toxic metals into the environment. The present review briefly discusses the cause and occurrence of AMD and the microbial diversity observed in such ecosystems. In addition, the bioremediation options are briefly presented with a discussion on the role of sulfidogenic biosystems in the bioremediation of the AMD.
Article
A native isolate, 9C, identified as Rhodococcus ruber (Genbank Accession number – KY029073) was studied for dibenzothiophene degradation and subsequent bio-desulphurization of three different sulphur bearing materials (NE coal containing organic sulphur; lignite containing pyritic sulphur and a calcined petroleum-coke) of Indian origin. The isolate could degrade 0.25 mM DBT through the 4S pathway within 7 days. Preliminary studies for sulphur removal using the 9C isolate indicated NE coal to be more amenable (29% sulphur removal) followed by Lignite (15.87%) and CPC (14.83%) respectively. Characterization through XRD and FTIR along with the proximate and ultimate analysis of all the samples provided more insights into the changes in calorific values as well as the chemical constitution of the samples following microbial treatment. Owing to the amenability of NE coal, the effect of time, size fraction and pulp density were optimized. The best bio-desulphurization conditions for NE coal indicated 36% total sulphur removal (organic–53%, pyritic–18% and sulphate sulphur–14% respectively). Analytical characterization studies confirmed that the energy value of the NE coal was not affected due to biodesulphurization, rather it contributed towards an increase in gross calorific value from 6698 cal/g to 6812 cal/g following microbial treatment.
Article
In this context, this study aims to reduce the harmful effects of coal combustion and to investigate the possibility of efficient use of Turkish lignite with high sulfur content. In this study, peroxide leaching process and accounts for approximately 35% of lignite reserves in Turkey total sulfur content of the garment was removed from lignite. For this purpose, the effect of H2O2 on 5%, 10%, 20%, and 30% solutions and H2SO4 on the sulfur removal using 0.05 N, 0.1 N, 0.15 N, and 0.2 N solutions separately and together were investigated. According to the results, increasing the H2O2 concentration from 5% to 30%, the total sulfur content of the coal sample was removed by approximately 75%. When 0.1 N H2SO4 and H2O2 were used together, about 93% of sulfur removal was realized. The originality of the study is that scenario 8 of 12 situations is both high standard chemical exergy value used for economic analysis, low CO2 emission value determined according to the life cycle assessment method used for environmental impact assessment, and 20-year operating cost calculated by current value estimation method. The lowest value indicates that 20% of H2SO4 is suitable for the establishment of the desulphurization plant with a yield of 63.2% from 200 kg of coal per hour. The highest exergy efficiency value was calculated as 8,01782E-06 for the 8th scenario. So the 8th scenario should be applied for the establishment of a desulfurization plant for E.L. Due to the results, this study is an economical method of sulfur removal. The addition of H2SO4 to H2O2 has a synergistic effect on sulfur removal. In this study, a new perspective has been developed by using exergy calculation and life cycle methods apart from conventional methods while determining the economy.
Article
Research on coal desulfurization is very important for economic, social, and environmentally sustainable development. In this study, three batches of shake flask experiments were conducted for coal bio-desulfurization using Acidithiobacillus ferrooxidans to explore the relationship between microbial nutrients (iron-free M9 K medium) supply and coal bio-desulfurization efficiency. The results showed that the removal rates of pyritic sulfur and total sulfur from coal effectively increased following reintroduction of coal into the filtrate from previous batch. The removal rates of pyritic sulfur and total sulfur were 55.6% and 10.0%, 77.1% and 16.1%, and 86.5% and 28.2%, respectively, in the three batch experiments without iron-free M9 K medium addition. In contrast, the removal rates of pyritic sulfur and total sulfur reached 87.5% and 28.2%, 89.1% and 31.6%, and 92.0% and 29.1%, respectively, in the three batch experiments with 6.7% iron-free M9 K medium addition. However, addition of excessive iron-free M9 K medium was detrimental to coal bio-desulfurization because of the synthesis of jarosite (MFe3(SO4)2(OH)6, M = K+, NH4+) and gypsum (CaSO4·2H2O), which further declined the pyritic sulfur bio-oxidation efficiency and total sulfur removal efficiency.
Article
This study mainly combines single factor experiment with orthogonal experiment to systematically investigate the effects of particle size, inoculum amount, pH value of the medium, ultrasonication time and species of surfactant on biodesulfurization of the high sulfur coal from Shanxi by using Thiobacillus ferrooxidans, Escherichia coli and Pseudomonas putida. The results revealed that the dominant strain was Pseudomonas putida which attained 58.23% of total sulfur removal during 10 days at the particle size of -125 + 75 μm, pH of 6.0, inoculum amount of 25 mL, ultrasonication time of 60 mins and Tween 80 concentration of 0.1%. Analysis of raw coal and biotreated coal by FTIR spectroscopy and X-ray diffraction indicated a modification of the coal structure after biodesulfurization. The curves of thermogravimetry (TG) for raw coal and biotreated coal also showed that the temperature of the coal pyrolysis significantly reduced, which meant that the thermal stability of the coal after biodesulfurization was lowered than raw coal. And the energy value of coal was not affected in the biodesulfurization process. After treatment with Pseudomonas putida, its calorific value only increased from 6308 cal/g to 6326 cal/g. Liquid products after biodesulfurization were extracted with a series of organic solvents, and each extract was characterized by gas chromatography-mass spectrometry (GC/MS), indicating the presence of sulfur-containing organic compounds in the liquid phase product. Ultimately, following these characterization results, the desulfurization mechanisms of all three bacteria were derived.
Chapter
Combustion of fossil fuels with high levels of sulfur compounds such as dibenzothiophene and their alkylated derivatives leads to severe environmental pollution. The reduction of sulfur emissions from fossil fuels is one of the strict regulations imposed on petroleum refineries by environmental legislative councils of developed countries. The traditional hydrodesulfurization (HDS) process employed by oil industries demands extreme conditions like high pressure, temperature, etc., but is expensive and inefficient in removing recalcitrant polyaromatic sulfur hydrocarbons. In the recent past, biodesulfurization (BDS) using microorganisms to reduce the sulfur content in fuels has gained a lot of attention. This process stands at an advantage from HDS as it is cost-effective, eco-friendly, and requires ambient pressure and temperature conditions. Therefore, it can be considered a potential complementary process for the biorefining of fossil fuels. This chapter summarizes the current state of knowledge and recent advancements in the BDS of fossil fuels.
Article
Dibenzothiophene (DBT) and its derivatives are important constituents of organosulfur compound in fossil fuels, which can result in one type of “acid rain” after burning process. Several technologies and methods have been developed to detect DBT, but they can be sophisticated and expensive. We have developed a two-step in-situ reduction method to fabricate Ag NPs modified glass fiber paper for SERS detection of DBT and its derivatives in a convenient and cheap way. Different from previous reports showing DBT cannot be detected by SERS, the substrate fabricated by our method revealed DBT’s characteristic Raman peak at 1600cm⁻¹. The dense and multilayer Ag NPs on glass fiber provided abundant spatial surface for DBT absorption and chemical interaction with Ag NPs, which led to CHEM enhancement in SERS detection. The mechanism was verified by UV-visible absorption spectrum and calculated Raman spectra. There was a good linear relationship between the SERS intensity at 1600cm⁻¹ and the concentration of DBT solution between 1 × 10 ⁻⁵ and 1 × 10⁻³ mol/L and the limit of detection was 1× 10⁻⁶ mol/L. Spiked petrol sample was detected and the recovery rate of DBT is in the range of 94.53%-107.39%. This method provides a convenient and reliable way to detect DBT and its derivatives.
Article
The current study illustrates the growth kinetics of an efficient PAH and heterocyclic PAH degrading bacterial strain, Pseudomonas aeruginosa RS1 on fluorene (FLU) and dibenzothiophene (DBT) over the concentration 25-500 mg L-1 and their concomitant degradation kinetics. The specific growth rate (µ) was found to lie within the range of 0.32-0.57 day-1 for FLU and 0.24-0.45 day-1 for DBT. The specific substrate utilization rate (q) of FLU and DBT over the log growth phase was between 0.01 and 0.14 mg FLU mg VSS-1 day-1 for FLU and between 0.01 and 0.18 mg DBT mg VSS-1 day-1 for DBT, respectively. The µ and q values varied within a narrow range for both FLU and DBT and they did not follow any specific trend. Dissolution together with direct interfacial uptake was the possible uptake mechanism for both FLU and DBT. The q values over the log growth phase depicts the specific substrate transformation rates. Kirby-Bauer disc diffusion studies performed using an E. coli strain indicated accumulation of some toxic intermediates of FLU and DBT during their degradation. Decrease in TOC and toxicity towards the end of the degradation experiments indicates further utilization of the intermediates. Supplementary information: The online version contains supplementary material available at 10.1007/s13205-021-02742-7.
Article
Exploiting efficient and low-cost oxidative desulfurization methods is urgently needed for promoting the development of novel desulfurization technologies. In this work, the sulfur speciation in the mechanochemically activated and H2O2 oxidized coals was quantitatively characterized through X-ray absorption near-edge structure (XANES) and X-ray photoelectron spectroscopy (XPS). The influences of H2O2 concentration and particle size on the sulfur transformation were discussed. In addition, the synergistic mechanisms of mechanochemical activation and H2O2 oxidation on the removal of organic sulfur were focused. Finally, combined with the sulfur speciation and deconvolution analysis, the main SO2 precursors during the pyrolysis were elucidated. The results indicate that mechanochemical activation can promote the conversion from organic to inorganic sulfur by reducing the strength of C-S bond and accelerating the oxidation of thiophene and sulfide, which is beneficial to remove organic sulfur. On the other hand, the dissolution amount of sulfate in small particles decreases due to the decreased macropore volumes, complicated pore structure, and increased mass transfer resistance. Then, an optimal particle size around 20 μm (i.e., HN_23.9 and NMG_18.7) is observed for the studied coals, where the reduced amplitude of SO2 after the chemical oxidation reaches the maximum. Besides, a dilute oxidant concentration is needed for low-rank coal during the chemical removal of sulfur, which is conducive to reduce the cost. The findings shed light on elucidating the origination of sulfur oxides from a molecular level and further exploiting the new efficient and low-cost desulfurization technologies.
Article
COnsensus DEgenerate Hybrid Oligonucleotide Primers (CODEHOP) were developed for the detection of the dszB desulfinase gene (2'-hydroxybiphenyl-2-sulfinate desulfinase; EC 3.13.1.3) by polymerase chain reaction (PCR), which allow to reveal larger diversity than traditional primers. The new developed primers were used as molecular monitoring tool to drive a procedure for the isolation of desulfurizing microorganisms. The primers revealed a large dszB gene diversity in environmental samples, particularly in diesel-contaminated soil that served as inoculum for enrichment cultures. The isolation procedure using the dibenzothiophene sulfone (DBTO2) as sole sulfur source reduced drastically the dszB gene diversity. A dszB gene closely related to that carried by Gordonia species was selected. The desulfurization activity was confirmed by the production of desulfurized 2-hydroxybiphenyl (2-HBP). Metagenomic 16S rRNA gene sequencing showed that the Gordonia genus was represented at low abundance in the initial bacterial community. Such observation highlighted that the culture medium and conditions represent the bottleneck for isolating novel desulfurizing microorganisms. The new developed primers constitute useful tool for the development of appropriate cultural-dependent procedures, including medium and culture conditions, to access novel desulfurizing microorganisms useful for the petroleum industry.
Article
Bacterial growth and degradation experiments were conducted on carbazole (CBZ), fluorene (FLU) and dibenzothiophene (DBT) individually and in various mixture combinations using an efficient polynuclear aromatic hydrocarbon (PAH) degrading bacterial strain, Pseudomonas aeruginosa RS1. In single component systems, bacterial growth on CBZ (specific growth rate, μ = 0.99 day-1) was much higher compared to that on FLU (μ = 0.38 day-1) and DBT (μ = 0.33 day-1) and bacterial growth was inhibited in the presence of FLU and DBT in binary (μ = 0.64 day-1) and ternary (μ = 0.75 day-1) mixtures. Multisubstrate additive modelling indicated growth inhibition in all the systems. The degradation of the compounds was significantly inhibited in binary mixtures. While the degradation of the compounds in binary mixtures varied from 35 ± 4% to 73 ± 3%, their degradation varied from 61 ± 5% to 91 ± 4%, when applied as sole substrates and from 77 ± 3% to 96 ± 3%, when applied in a ternary mixture. Degradation experiments were also conducted in ternary mixtures using a 23 full factorial design and the results were examined using analysis of variance (ANOVA) and Tukey's honest significant difference (HSD) tests. At a low concentration of the heterocyclics, CBZ and DBT (5 mg L-1 each), the degradation of the PAH, FLU, was significantly enhanced (from 81 ± 1% to 93 ± 0.3%) when its concentration was increased from 5 to 30 mg L-1. The full factorial design can provide valuable insights into substrate interaction effects in mixtures.
Article
Heterocyclic polynuclear aromatic hydrocarbons (PAHs) have been detected in all environmental matrices at few ppb to several ppm concentrations and they are characterized by high polarity. Some heterocyclic PAHs are mutagenic and carcinogenic to humans and various organisms. Despite being potent environmental pollutants, these compounds have received less attention. This paper focuses on the sources and occurrence of these compounds and their microbial degradation using diverse species of bacteria, fungi, and algae. Complete removal of 1.8 to 2614 mg/L of nitrogen heterocyclic PAH (PANH), 0.27 to 184 mg/L of sulfur heterocyclic PAH (PASH), and 0.6 to 120 mg/L of oxygen heterocyclic PAH (PAOH) compounds by various microbial species was observed between 3 h to 18 days, 8 h to 6 days, and 4 h to 250 h, respectively under aerobic condition. Strategies for enhancing the removal of heterocyclic PAHs from aquatic systems are also discussed along with the challenges.
Article
The present work investigated an effective method to remove organic sulfur in coal utilizing different microorganisms (Nocardia mangyaensis and Pseudomonas putida). The most obvious finding to emerge from the sulfur forms analysis is that the organic sulfur removal of these two bacterial strains on Yunnan bumuga high sulfur coal were 61.58% and 54.19%, respectively. This result may be confirmed by the FTIR analyses that there were obvious decreases of intensity after biotreatment in the C‐S bond. Besides, the results of X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS) showed that major mineralogical phases in the forms of kaolinite and pyrite exist in raw coal. And more than 80% of thiophene and sulfoxide in the raw coal were removed by Nocardia mangyaensis and Pseudomonas putida. In addition, the results of the thermogravimetric analysis indicated that the combustion performance of biotreated coal samples was better than that of raw coal, and the most probable models to describe the combustion kinetics for biotreated coal and raw coal at different stages were obtained by the Arrhenius method and Coats‐Redfern method. This article is protected by copyright. All rights reserved.
Article
This study explored the utilization of soil sorbed carbazole (CBZ), fluorene (FLU), and dibenzothiophene (DBT) by an efficient polynuclear aromatic hydrocarbon (PAH) and heterocyclic PAH degrading bacterial strain, Pseudomonas aeruginosa RS1, inoculated in soil microcosms. Biotic and abiotic microcosm studies were set up with Tenax beads, which sequestered the desorbed compounds from the aqueous phase. Soil phase decay profiles obtained for single, binary and ternary systems containing soil sorbed CBZ, FLU, and DBT under both biotic and abiotic conditions were fitted using a first-order decay model. Across all compounds, the first-order decay coefficient under biotic condition (kb, varying from 5.77 ×10⁻⁴ to 40 ×10-4 hr⁻¹) was 2 to 5.2 times higher than the corresponding values obtained under abiotic condition (ka, varying from 1.3 ×10⁻⁴ to 13.4 ×10-4 hr⁻¹), indicating direct interfacial uptake of soil sorbed compounds by P. aeruginosa. Although the model fitted the abiotic decay profiles well, the model fits were not consistently good for the biotic profiles. In abiotic systems, the mass of the compounds was conserved, while in biotic systems, microbial degradation of both desorbed and sorbed compounds caused loss of CBZ, FLU, and DBT, and sequestration in Tenax was 1.3 to 5-fold lower.
Article
Mineralogically distinct coal samples respond differentially to microbial attack. In the present study, a mixed meso-acidophilic bacterial consortium predominantly comprising of Acidithiobacillus ferrooxidans strain was investigated for its biodesulphurization abilities for three distinct sulphur bearing samples (Goa CPC, Rajasthan Lignite, Assam Coal) of Indian origin in iron (9K+) and iron-free (9K-) media. A media devoid of Fe (II) iron was seen to be more effective for sulphur removal with maximum desulphurization of 45.19% for Assam coal followed by 36.8% for Rajasthan Lignite and 23.38% for CPC respectively. The proximate analysis, FTIR patterns and XRD analysis of the samples provided better insights into understanding the mineralogical and compositional changes in the coal matrix. Owing to the higher efficiency, Assam coal was additionally subjected to further optimization studies and characterization of the treated coal through TGA. The study indicated that the gross calorific values for all the samples increased following microbial treatment in 9K- media thereby providing a scope for further scale-up studies.
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Successful biodegradation process of different complexes required attention to biological parameters (such as choice of microorganisms), control of the chemical and physical environment (pH, redox potential, temperature and metallic ions) and consideration of the metal mines condition. In this context, the present paper presents the study regarding the main interactions between acidophilic bacteria and toxic metal ions can occur through active processes, involving the metabolic sequences of living microorganisms or passive processes, independent of cellular metabolism. The acidophilic bacterial cultures used in the degradation experiments of organic compounds were selected on the basis of their capacity to hydrolyse the starch in the presence of different inorganic forms of heavy metal ions The heterotrophic bacterial capacity by producing organic acid was very high, which confirm the adaptation of these populations to higher concentrations of heavy metallic ions. Comparative results bring an improved bacterial growth and sensitivity to specific environmental conditions and bacterial populations although the effect is not maintained after longer times. Our analysis regarding the efficiency of extracellular enzymes from Acidiphilium populations shows continuous agitation conditions (21 days) in the presence of 2-3g/l starch induce an increased extracellular hydrolytic activity (50-60%) when sulphates is present in the environment.
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In this study, the resting cells of Gordonia sp. WQ-01A, a DBT-desulfurizing strain, were immobilized by calcium alginate. Batch DBT biodesulfurization experiments using immobilized cells and n-dodecane as the oil phase were conducted in fermenter under varying operating conditions such as initial DBT concentration, bead loading and the oil phase volume fraction. When the initial DBT concentration is 0.5, 1 and 5 mmol L-1, the DBT concentration dropped almost to zero after t = 40, 60 and 100 hours, respectively. The influence of bead loading and the oil-phase volume fraction was small to the DBT biodesulfurization. Furthermore, a mathematical model was proposed to simulate the batch DBT biodesulfurization process in an oil-water-immobilization system, which took into account the internal and external mass transfer resistances of DBT and oxygen, and the intrinsic kinetics of bacteria. To validate this model, the comparison between the model simulations and the experimental measurements of DBT concentration profiles in the oil phase was carried out and the agreement is very good. In addition, the time and radius courses of DBT and oxygen concentrations within the alginate gel beads were reasonably predicted by the proposed model.
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Chalcopyrite is the primary copper mineral used for production of copper metal. Today, as a result of rapid industrialization, there has been enormous demand to profitably process the low grade chalcopyrite and "dirty" concentrates through bioleaching. In the current scenario, heap bioleaching is the most advanced and preferred eco-friendly technology for processing of low grade, uneconomic/difficult-to-enrich ores for copper extraction. This paper reviews the current status of chalcopyrite bioleaching. Advanced information with the attempts made for understanding the diversity of bioleaching microorganisms; role of OMICs based research for future applications to industrial sectors and chemical/microbial aspects of chalcopyrite bioleaching is discussed. Additionally, the current progress made to overcome the problems of passivation as seen in chalcopyrite bioleaching systems have been conversed. Furthermore, advances in the designing of heap bioleaching plant along with microbial and environmental factors of importance have been reviewed with conclusions into the future prospects of chalcopyrite bioleaching. Copyright © 2015 Elsevier Ltd. All rights reserved.
Chapter
Microbe–mineral interactions are very pervasive in nature. Since coal is a chief source of nonrenewable energy and finds its application in a wide variety of sectors, the importance of microbe–mineral interaction is indispensible for developing a sustainable microbial coal biotechnology. The underlying necessity of microbe–mineral interaction is also linked with acid mine drainage that is a universal environmental problem in iron- and sulfur-rich environments. In the view of the fact that microbes act as a storehouse of several novel biomolecules or enzymes, they can be used for bioprocessing on an industrial scale incorporating innovative ideas and advanced technologies. The coal mines comprise of several synergistic interactions occurring between microbes and minerals which vary according to pH, temperature, mineralogy, and metal concentration, ultimately forming a viable microbial community.
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For an efficient operation in biodesulfurization of petroleum and related fuels, the aqueous solubility of insoluble or very slightly soluble sulfur compounds contained in the petroleum products has to be increased. In this study, polyoxyethylene nonionic surfactants were used in order to enhance the aqueous solubility of insoluble or very slightly soluble sulfur compounds contained in the bunker-C oil and the solubilized sulfur contents in the aqueous surfactant solutions were measured by X-ray sulfur spectrophotometer. The most hydrophobic surfactant used during this study showed the maximum solubilization capacity for sulfur compounds contained in the bunker-C oil and the solubilization of sulfur compounds was found to increase with temperature and to be abruptly increased at above 5 wt % surfactant concentrations. It was found that Tergitol series surfactants showed higher solubilizing capacity than Neodol series surfactants presumably due to the disruption of the regular packing in the hydrocarbon region of the surfactant micellar aggregates and that the addition of a cosurfactant and/or an electrolyte increased the solubilization of sulfur compounds in the bunker-C oil. It was also shown that partitioning phenomena were shown to be significant with a hydrophobic surfactant especially at high temperature and pH of the Tergitol surfactant solution did not affect the solubilization of sulfur compounds. The growth of M6 sulfur-reducing bacteria was not greatly affected by the addition of both nonionic surfactant and cosurfactant. Desulfurization experiments with M6 sulfur-reducing bacteria showed that the biodesulfurization rate of bunker-C oil was enhanced with addition of nonionic surfactant and these data suggested the potential applicability of surfactant to the actual biodesulfurization system.
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Coal collected from Meghalaya state situated in northeastern (NE) region of India contains about 6.17% total sulphur (4.7% organic) with a gross calorific value of 26,208 J/g. In the present study, the coal sample was subjected to biodesulphurization along with optimization of various process parameters using a bacteria isolated from the native coal mine site. The native bacterium was identified to be Sinomonas flava 1C and reported first time for the capability to remove about 40% of sulphur from the coal. An innovative two-step sequential leaching using S. flava 1C followed by Acidithiobacillus ferrooxidans was used in the present study to enhance desulphurization. Sequential leaching resulted in 50-53% of sulphur removal from the coal sample. Sequential leaching reduced the sulphur content to 3.08% (organic 2.15% + pyritic 0.1% and 0.85% of sulphate sulphur) in -500+300 mu m size fraction of coal. Analytical characterization indicated that the energy value of coal was not affected adversely due to the biodesulphurization process rather its calorific value increased from 26,208 J/g to 29,481 J/g.
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Dumping of low-grade chalcopyrite encompasses several environmental problems. Despite slow dissolution rate, meso-acidophilic bioleaching is preferred for the extraction of copper from such ores. In the present study, meso-acidophilic bioleaching of a low-grade chalcopyrite in presence of an acid-processed waste newspaper (PWp) is discussed for the first time. The study illustrated a strong catalytic response of PWp with enhanced bio-recovery of copper from acid-conditioned chalcopyrite. A maximum of 99.13% copper recovery (0.36% Cu dissolution/day) was obtained in 6 days of bioleaching in presence of 2 gL- 1 PWp in contrast to only 5.7% copper in its absence. FTIR analysis of bioleached residues revealed similar spectral patterns to the original acid-conditioned ore in presence of PWp, thus indicating less development of passivation layer which was also confirmed through a complementary raman characterization of the bioleached residues. Further, a reaction mechanism (chemistry) was proposed suggesting the possible role of PWp as the electron donor under oxygen limiting conditions which facilitated microbial reduction of Fe (III). The resulting biochemical changes provided an energy source for the bacteria, thus allowing free flow of electrons through the ore surface, thus contributing towards enhanced bioleaching of copper.
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Microwave heating has been used in desulfurization of coal. Removal of organic sulfur and organic sulfur forms alterations of Xishan (XS) coal and Yunnan (YN) coal was investigated under microwave and ultrasonic irradiation. The results showed the optimum conditions for desulfurization were 50 min and 560 W for microwave and ultrasound for both coals. The desulfurization rate was maximum 23.53% for XS coal and 76.58% for YN coal. The effect of combining microwave and ultrasonic irradiation on desulfurization was stronger than simple microwave irradiation. The content of sulphone sulfur in coal was increased from the XPS after microwave and ultrasonic co-enhanced oxidative desulfurization.
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One of the microbial products produced from dibenzothiophene by Pseudomonas abikonensis or P. jianii was identified as a new substance, trans-4 [2-(3-hydroxy)-thianaphthenyl]-2-oxo-3-butenoic acid, and the other as its hemiacetal form. From the structures of the products, an oxidation pathway of dibenzothiophene was suggested. Moreover, the culture broth and the isolated products were examined for plant growth activities on rice plants.
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Up-to-date information on the microbiological method of fuel desulfurization has been systematized and the ways of increasing the efficiency of this method have been considered. The prospective uses of biochemical methods for the specific elimination of sulfur from petroleum and the production of fuel conforming to modern standards are discussed. Reports on the novel desulfurization procedure that employs commercial preparations of enzymes and proteins are analyzed in detail.
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A microbial fungus, Cunninghamella elegans var. echinulata, oxidized not only benzothiophene but also methyl-, ethyl-, and diethyl-benzothiophene to give sulfoxide compounds, and some of them could not be converted by previous reported biodesulfurizing bacteria.
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The removal of sulfur in coal before its combustion can reduce its environmental pollution, and microbial desulfurization should have good application prospects. Some species of bacteria have been used in the process of coal desulfurization, and our previous study demonstrated that mixed culture should be more efficient than pure culture by shaking cultivation. In this study, column leaching was investigated, due to its similarity to the industrial heap leaching. The mixed culture consisted of three strains of bacteria, which were Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans respectively. The ratio of the three strains of bacteria was 1: 1: 1. The column (50 cm height, 650 mm Inner Diameter) bioleaching experiments were carried out at ambient temperature. After desulfurization for 18 days, the ultimate desulfurization rate was 28.66% for total sulfur, which was higher than the previous study of J.Cara (with total sulfur desulfurization rate for 24% after 125 days). This study showed that ferric ions should be in proper concentration, and Leptospirillum ferrooxidans might be in lower ratio for reducing the precipitation of jarosite and improving the efficient of coal desulfurization.
Article
AimTo isolate actinomycete spp with the ability to desulfurize sulfur containing heterocyclic compounds present in petroleum.Methods and ResultsEnrichment cultures were set up to select and isolate sulfur heterocycle metabolizing soil microorganisms. Screening of the microbial isolates for the desulfurization property led to isolation of R3. The isolate was characterized by PCR screening of 16Sr RNA genes, and classical taxonomic investigations. HPLC analysis of the desulfurization assays with R3 showed ~ 85% transformation of dibenzothiophene (270 μmol l−1), present as the sole sulfur source in basal salt medium, in 4 days. Production of the desulfurized dibenzothiophene metabolite; 2-hydroxybiphenyl, was confirmed by GC/MS analyses. GC/MS analyses also established the ability of R3 to transform benzothiophene to benzothiophene-1-oxide and benzothiophene-1, 1-dioxide, and thianthrene to thianthrene-5-oxide. PCR primers computed based on the desulfurization operon (dsz ABC) of Rhodococcus erythropolis IGTS8 yielded the predicted amplification products with R3 genomic DNA as template. Southern hybridization and restriction endonuclease digestion profiles indicated that R3 amplicons were homologous to dsz AB.Conclusions The enrichment method used in this study yielded an environmental isolate with the ability to transform multiple sulfur heterocycles. The isolate R3 has taxonomic proximity to the Oerskovia sp, order Actinomycetales. The isolate R3 selectively removes sulfur from dibenzothiophene yielding 2-hydroxybiphenyl and sulfate. R3 also transforms benzothiophene and thianthrene in a sulfur targeted manner. The desulfurization genes in R3 bear similarity to those in R. erythropolis IGTS8.Significance and Impact of the studyThe actinomycetes present in soil, can remove sulfur from different sulfur heterocycle substrates and have potential as biodesulfurization catalysts.This article is protected by copyright. All rights reserved.
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