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Advancing Desulfurization in the Model Biocatalyst Rhodococcus qingshengii IGTS8 via an In Locus Combinatorial Approach. Appl Environ Microbiol 2023; 89:e0197022. [PMID: 36688659 PMCID: PMC9973023 DOI: 10.1128/aem.01970-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Biodesulfurization poses as an ideal replacement to the high cost hydrodesulfurization of the recalcitrant heterocyclic sulfur compounds, such as dibenzothiophene (DBT) and its derivatives. The increasingly stringent limits on fuel sulfur content intensify the need for improved desulfurization biocatalysts, without sacrificing the calorific value of the fuel. Selective sulfur removal in a wide range of biodesulfurization strains, as well as in the model biocatalyst Rhodococcus qingshengii IGTS8, occurs via the 4S metabolic pathway that involves the dszABC operon, which encodes enzymes that catalyze the generation of 2-hydroxybiphenyl and sulfite from DBT. Here, using a homologous recombination process, we generate two recombinant IGTS8 biocatalysts, harboring native or rearranged, nonrepressible desulfurization operons, within the native dsz locus. The alleviation of sulfate-, methionine-, and cysteine-mediated dsz repression is achieved through the exchange of the native promoter Pdsz, with the nonrepressible Pkap1 promoter. The Dsz-mediated desulfurization from DBT was monitored at three growth phases, through HPLC analysis of end product levels. Notably, an 86-fold enhancement of desulfurization activity was documented in the presence of selected repressive sulfur sources for the recombinant biocatalyst harboring a combination of three targeted genetic modifications, namely, a dsz operon rearrangement, a native promoter exchange, and a dszA-dszB overlap removal. In addition, transcript level comparison highlighted the diverse effects of our genetic engineering approaches on dsz mRNA ratios and revealed a gene-specific differential increase in mRNA levels. IMPORTANCE Rhodococcus is perhaps the most promising biodesulfurization genus and is able to withstand the harsh process conditions of a biphasic biodesulfurization process. In the present work, we constructed an advanced biocatalyst harboring a combination of three genetic modifications, namely, an operon rearrangement, a promoter exchange, and a gene overlap removal. Our homologous recombination approach generated stable biocatalysts that do not require antibiotic addition, while harboring nonrepressible desulfurization operons that present very high biodesulfurization activities and are produced in simple and low-cost media. In addition, transcript level quantification validated the effects of our genetic engineering approaches on recombinant strains' dsz mRNA ratios and revealed a gene-specific differential increase in mRNA levels. Based on these findings, the present work can pave the way for further strain and process optimization studies that could eventually lead to an economically viable biodesulfurization process.
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Bacterial Biological Factories Intended for the Desulfurization of Petroleum Products in Refineries. FERMENTATION-BASEL 2023. [DOI: 10.3390/fermentation9030211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/02/2023]
Abstract
The removal of sulfur by deep hydrodesulfurization is expensive and environmentally unfriendly. Additionally, sulfur is not separated completely from heterocyclic poly-aromatic compounds. In nature, several microorganisms (Rhodococcus erythropolis IGTS8, Gordonia sp., Bacillus sp., Mycobacterium sp., Paenibacillus sp. A11-2 etc.) have been reported to remove sulfur from petroleum fractions. All these microbes remove sulfur from recalcitrant organosulfur compounds via the 4S pathway, showing potential for some organosulfur compounds only. Activity up to 100 µM/g dry cell weights is needed to meet the current demand for desulfurization. The present review describes the desulfurization capability of various microorganisms acting on several kinds of sulfur sources. Genetic engineering approaches on Gordonia sp. and other species have revealed a variety of good substrate ranges of desulfurization, both for aliphatic and aromatic organosulfur compounds. Whole genome sequence analysis and 4S pathway inhibition by a pTeR group inhibitor have also been discussed. Now, emphasis is being placed on how to commercialize the microbes for industrial-level applications by incorporating biodesulfurization into hydrodesulfurization systems. Thus, this review summarizes the potentialities of microbes for desulfurization of petroleum. The information included in this review could be useful for researchers as well as the economical commercialization of bacteria in petroleum industries.
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Nanocatalysts for Oxidative Desulfurization of Liquid Fuel: Modern Solutions and the Perspectives of Application in Hybrid Chemical-Biocatalytic Processes. Catalysts 2021. [DOI: 10.3390/catal11091131] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
In this paper, the current advantages and disadvantages of using metal-containing nanocatalysts (NCs) for deep chemical oxidative desulfurization (ODS) of liquid fuels are reviewed. A similar analysis is performed for the oxidative biodesulfurization of oil along the 4S-pathway, catalyzed by various aerobic bacterial cells of microorganisms. The preferences of using NCs for the oxidation of organic sulfur-containing compounds in various oil fractions seem obvious. The text discusses the development of new chemical and biocatalytic approaches to ODS, including the use of both heterogeneous NCs and anaerobic microbial biocatalysts that catalyze the reduction of chemically oxidized sulfur-containing compounds in the framework of methanogenesis. The addition of anaerobic biocatalytic stages to the ODS of liquid fuel based on NCs leads to the emergence of hybrid technologies that improve both the environmental characteristics and the economic efficiency of the overall process. The bioconversion of sulfur-containing extracts from fuels with accompanying hydrocarbon residues into biogas containing valuable components for the implementation of C-1 green chemistry processes, such as CH4, CO2, or H2, looks attractive for the implementation of such a hybrid process.
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Biodesulfurization of diesel oil in oil–water two phase reaction system by Gordonia sp. SC-10. Biotechnol Lett 2019; 41:547-554. [DOI: 10.1007/s10529-019-02663-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2018] [Accepted: 03/20/2019] [Indexed: 10/27/2022]
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Enzymatic Desulfurization of Crude Oil and Its Fractions: A Mini Review on the Recent Progresses and Challenges. ARABIAN JOURNAL FOR SCIENCE AND ENGINEERING 2019. [DOI: 10.1007/s13369-019-03800-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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6
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Microbial desulfurization of ground tire rubber (GTR): Characterization of microbial communities and rheological and mechanical properties of GTR and natural rubber composites (GTR/NR). Polym Degrad Stab 2019. [DOI: 10.1016/j.polymdegradstab.2018.12.021] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Characterization of the genome of a Nocardia strain isolated from soils in the Qinghai-Tibetan Plateau that specifically degrades crude oil and of this biodegradation. Genomics 2018; 111:356-366. [PMID: 29474825 DOI: 10.1016/j.ygeno.2018.02.010] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2018] [Accepted: 02/16/2018] [Indexed: 11/22/2022]
Abstract
A strain of Nocardia isolated from crude oil-contaminated soils in the Qinghai-Tibetan Plateau degrades nearly all components of crude oil. This strain was identified as Nocardia soli Y48, and its growth conditions were determined. Complete genome sequencing showed that N. soli Y48 has a 7.3 Mb genome and many genes responsible for hydrocarbon degradation, biosurfactant synthesis, emulsification and other hydrocarbon degradation-related metabolisms. Analysis of the clusters of orthologous groups (COGs) and genomic islands (GIs) revealed that Y48 has undergone significant gene transfer events to adapt to changing environmental conditions (crude oil contamination). The structural features of the genome might provide a competitive edge for the survival of N. soli Y48 in oil-polluted environments and reflect the adaptation of coexisting bacteria to distinct nutritional niches.
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Abstract
1. Thianthrene is a sulfur-containing tricyclic molecule distributed widely within the macrostructure of hydrocarbon fossil fuels. Identified nearly 150 years ago, its chemistry has been widely explored leading to insights into reaction mechanisms and radical ion formation. 2. It has been claimed to have therapeutic application in the treatment of dermal infections and to interfere with enzyme and nucleic acid function, but appears to have little toxicity. 3. Following its oral administration to the rat, the majority remained within the gastrointestinal tract. After three days, about 88% was detected in the combined excreta with the remainder still within the animal. It is readily taken up into fish from the surrounding aqueous environment and has been placed within the "bioaccumulative category" to be regarded with concern. 4. Mammalian metabolism appeared to be restricted to ring carbon oxidation and subsequent glucuronic acid conjugation. Small amounts of sulfoxide and disulfoxide were also formed. No ring degradation was evident. Microorganisms similarly undertook aromatic ring hydroxylation but were able also to rupture the ring system by attacking the carbon-sulfur linkages and thereby degrading the molecule.
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Affiliation(s)
- Steve C Mitchell
- a Computational and Systems Medicine, Imperial College London , London , UK and
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Tatangelo V, Mangili I, Caracino P, Anzano M, Najmi Z, Bestetti G, Collina E, Franzetti A, Lasagni M. Biological devulcanization of ground natural rubber by Gordonia desulfuricans DSM 44462T strain. Appl Microbiol Biotechnol 2016; 100:8931-42. [DOI: 10.1007/s00253-016-7691-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Revised: 06/13/2016] [Accepted: 06/15/2016] [Indexed: 10/21/2022]
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Parravicini F, Brocca S, Lotti M. Evaluation of the Conformational Stability of Recombinant Desulfurizing Enzymes from a Newly Isolated Rhodococcus sp. Mol Biotechnol 2015; 58:1-11. [PMID: 26515071 DOI: 10.1007/s12033-015-9897-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Metabolic pathways of aerobic bacteria able to assimilate sulfur can provide biocatalysts for biodesulfurization of petroleum and of other sulfur-containing pollutants. Of major interest is the so-called "4S pathway," in that C-S bonds are specifically cleaved leaving the carbon skeleton of substrates intact. This pathway is carried out by four enzymes, named Dsz A, B, C, and D. In view of a possible application of recombinant Dsz enzymes in biodesulfurization treatments, we have investigated the structural features of enzymes cloned from a Rhodococcus strain isolated from polluted environmental samples and their resistance to temperature (20-95 °C) and to organic solvents (5, 10, and 20 % v/v methanol, acetonitrile, hexane, and toluene). Changes in protein structures were assessed by circular dichroism and intrinsic fluorescence spectroscopy. We found that all Dsz proteins are unfolded by temperatures in the range 45-60 °C and by all solvents tested, with the most dramatic effect being produced by toluene. These results suggest that stabilization of the biocatalysts by protein engineering will be necessary for developing biodesulfurization technologies based on Dsz enzymes.
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Affiliation(s)
- Federica Parravicini
- Department of Biotechnology and Biosciences, State University of Milano-Bicocca, Piazza della Scienza 2, 20126, Milan, Italy
| | - Stefania Brocca
- Department of Biotechnology and Biosciences, State University of Milano-Bicocca, Piazza della Scienza 2, 20126, Milan, Italy
| | - Marina Lotti
- Department of Biotechnology and Biosciences, State University of Milano-Bicocca, Piazza della Scienza 2, 20126, Milan, Italy.
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Mohamed MES, Al-Yacoub ZH, Vedakumar JV. Biocatalytic desulfurization of thiophenic compounds and crude oil by newly isolated bacteria. Front Microbiol 2015; 6:112. [PMID: 25762990 PMCID: PMC4327732 DOI: 10.3389/fmicb.2015.00112] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Accepted: 01/29/2015] [Indexed: 12/23/2022] Open
Abstract
Microorganisms possess enormous highly specific metabolic activities, which enable them to utilize and transform nearly every known chemical class present in crude oil. In this context, one of the most studied biocatalytic processes is the biodesulfurization (BDS) of thiophenic sulfur-containing compounds such as benzothiophene (BT) and dibenzothiophene (DBT) in crude oils and refinery streams. Three newly isolated bacterial strains, which were affiliated as Rhodococcus sp. strain SA11, Stenotrophomonas sp. strain SA21, and Rhodococcus sp. strain SA31, were enriched from oil contaminated soil in the presence of DBT as the sole S source. GC-FID analysis of DBT-grown cultures showed consumption of DBT, transient formation of DBT sulfone (DBTO2) and accumulation of 2-hydroxybiphenyl (2-HBP). Molecular detection of the plasmid-borne dsz operon, which codes for the DBT desulfurization activity, revealed the presence of dszA, dszB, and dszC genes. These results point to the operation of the known 4S pathway in the BDS of DBT. The maximum consumption rate of DBT was 11 μmol/g dry cell weight (DCW)/h and the maximum formation rate of 2-HBP formation was 4 μmol/g DCW/h. Inhibition of both cell growth and DBT consumption by 2-HBP was observed for all isolates but SA11 isolate was the least affected. The isolated biocatalysts desulfurized other model DBT alkylated homologs. SA11 isolate was capable of desulfurizing BT as well. Resting cells of SA11 exhibited 10% reduction in total sulfur present in heavy crude oil and 18% reduction in total sulfur present in the hexane-soluble fraction of the heavy crude oil. The capabilities of the isolated bacteria to survive and desulfurize a wide range of S compounds present in crude oil are desirable traits for the development of a robust BDS biocatalyst to upgrade crude oils and refinery streams.
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Affiliation(s)
| | - Zakariya H Al-Yacoub
- Biotechnology, Research and Development Center, Saudi Aramco, Dhahran Saudi Arabia
| | - John V Vedakumar
- Biotechnology, Research and Development Center, Saudi Aramco, Dhahran Saudi Arabia
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Alves L, Paixão SM. Fructophilic behaviour of Gordonia alkanivorans strain 1B during dibenzothiophene desulfurization process. N Biotechnol 2013; 31:73-9. [PMID: 24012483 DOI: 10.1016/j.nbt.2013.08.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Revised: 08/15/2013] [Accepted: 08/22/2013] [Indexed: 01/23/2023]
Abstract
Biodesulfurization (BDS) aims at the removal of recalcitrant sulfur from fossil fuels at mild operating conditions with the aid of microorganisms. These microorganisms can remove sulfur from dibenzothiphene (DBT), a model compound, or other polycyclic aromatic used as sulfur source, making BDS an easy and environmental friendly process. Gordonia alkanivorans strain 1B has been described as a desulfurizing bacterium, able to desulfurize DBT to 2-hydroxybiphenyl (2-HBP), the final product of the 4S pathway, using d-glucose as carbon source. However, both cell growth and desulfurization can be largely affected by the nutrient composition of the growth medium, due to cofactor requirements of many enzymes involved in the BDS biochemical pathway. In this study, the main goal was to investigate the influence of several sugars, as carbon source, on the growth and DBT desulfurization ability of G. alkanivorans strain 1B. The results of desulfurization tests showed that the lowest values for the growth rate (0.025 hour(-1)) and for the overall 2-HBP production rate (1.80 μm/hour) by the strain 1B were obtained in glucose grown cultures. When using sucrose, the growth rate increase exhibited by strain 1B led to a higher biomass productivity, which induced a slightly increase in the 2-HBP production rate (1.91 μm/hour), conversely in terms of 2-HBP specific production rate (q2-HBP) the value obtained was markedly lower (0.718 μmol/g/hour in sucrose versus 1.22 μmol/g/hour in glucose). When a mixture of glucose and fructose was used as carbon source, strain 1B reached a value of q2-HBP=1.90 μmol/g/hour, close to that in fructose (q2-HBP=2.12 μmol/g/hour). The highest values for both cell growth (μ=0.091 hour(-1)) and 2-HPB production (9.29μm/hour) were obtained when strain 1B was desulfurizing DBT in the presence of fructose as the only carbon source, indicating a fructophilic behaviour by this bacterium. This fact is in agreement with the highest value of biomass productivity by strain 1B be in fructose, which resulted in a higher amount cells fulfilling the DBT-desulfurization. The greater number of functional cells conducted to a more effectiveness BDS process by strain 1B, as they attained a q2-HBP about 74% higher than in glucose grown cultures. Moreover, this significant BDS enhancement can better be observed in terms of the overall 2-HBP production rate, which increased over 5-fold, from 1.80 μm/hour (in glucose) to 9.29 μm/hour (in fructose).
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Affiliation(s)
- Luís Alves
- LNEG - Instituto Nacional de Energia e Geologia, IP, Unidade de Bioenergia, Estrada do Paço do Lumiar, 22, 1649-038 Lisboa, Portugal.
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Luo Q, Hiessl S, Steinbüchel A. Functional diversity of Nocardia in metabolism. Environ Microbiol 2013; 16:29-48. [PMID: 23981049 DOI: 10.1111/1462-2920.12221] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Revised: 07/12/2013] [Accepted: 07/19/2013] [Indexed: 11/29/2022]
Abstract
Bacteria affiliated in the genus Nocardia are aerobic and Gram-positive actinomycetes that are widely found in aquatic and terrestrial habitats. As occasional pathogens, several of them cause infection diseases called 'nocardiosis' affecting lungs, central nervous system, cutaneous tissues and others. In addition, members of the genus Nocardia exhibit an enormous metabolic versatility. On one side, many secondary metabolites have been isolated from members of this genus that exhibit various biological activities such as antimicrobial, antitumor, antioxidative and immunosuppressive activities. On the other side, many species are capable of degrading or converting aliphatic and aromatic toxic hydrocarbons, natural or synthetic polymers, and other widespread environmental pollutants. Because of these valuable properties and the application potential, Nocardia species have attracted much interest in academia and industry in recent years. A solid basis of genetic tools including a set of shuttle vectors and an efficient electroporation method for further genetic and metabolic engineering studies has been established to conduct efficient research. Associated with the increasing data of nocardial genome sequences, the functional diversity of Nocardia will be much faster and better understood.
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Affiliation(s)
- Quan Luo
- Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster, Corrensstraße 3, 48149, Münster, Germany
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Aminsefat A, Rasekh B, Ardakani MR. Biodesulfurization of dibenzothiophene by Gordonia sp. AHV-01 and optimization by using of response surface design procedure. Microbiology (Reading) 2012. [DOI: 10.1134/s0026261712020026] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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Characterization of bacterial strains capable of desulphurisation in soil and sediment samples from Antarctica. Extremophiles 2010; 14:475-81. [PMID: 20737178 DOI: 10.1007/s00792-010-0326-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2010] [Accepted: 08/04/2010] [Indexed: 10/19/2022]
Abstract
The presence of sulphur in fossil fuels and the natural environment justifies the study of sulphur-utilising bacterial species and genes involved in the biodesulphurisation process. Technology has been developed based on the natural ability of microorganisms to remove sulphur from polycyclic aromatic hydrocarbon chains. This biotechnology aims to minimise the emission of sulphur oxides into the atmosphere during combustion and prevent the formation of acid rain. In this study, the isolation and characterization of desulphurising microorganisms in rhizosphere and bulk soil samples from Antarctica that were either contaminated with oil or uncontaminated was described. The growth of selected isolates and their capacity to utilise sulphur based on the formation of the terminal product of desulphurisation via the 4S pathway, 2-hydroxybiphenyl, was analysed. DNA was extracted from the isolates and BOX-PCR and DNA sequencing were performed to obtain a genomic diversity profile of cultivable desulphurising bacterial species. Fifty isolates were obtained showing the ability of utilising dibenzothiophene as a substrate and sulphur source for maintenance and growth when plated on selective media. However, only seven genetically diverse isolates tested positive for sulphur removal using the Gibbs assay. DNA sequencing revealed that these isolates were related to the genera Acinetobacter and Pseudomonas.
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Kalme S, Parshetti G, Gomare S, Govindwar S. Diesel and Kerosene Degradation by Pseudomonas desmolyticum NCIM 2112 and Nocardia hydrocarbonoxydans NCIM 2386. Curr Microbiol 2008; 56:581-6. [DOI: 10.1007/s00284-008-9128-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2007] [Accepted: 06/20/2007] [Indexed: 11/24/2022]
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Santos SCC, Alviano DS, Alviano CS, Goulart FRV, de Pádula M, Leitão AC, Martins OB, Ribeiro CMS, Sassaki MYM, Matta CPS, Bevilaqua J, Sebastián GV, Seldin L. Comparative studies of phenotypic and genetic characteristics between two desulfurizing isolates of Rhodococcus erythropolis and the well-characterized R. erythropolis strain IGTS8. J Ind Microbiol Biotechnol 2007; 34:423-31. [PMID: 17333091 DOI: 10.1007/s10295-007-0214-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2006] [Accepted: 02/04/2007] [Indexed: 11/26/2022]
Abstract
Two Rhodococcus erythropolis isolates, named A66 and A69, together with the well-characterized R. erythropolis strain IGTS8 were compared biochemically and genetically. Both isolates, like strain IGTS8, desulfurized DBT to 2-hydroxybiphenyl (2-HBP), following the 4S pathway of desulfurization. Strain IGTS8 showed the highest (81.5%) desulfurization activity in a medium containing DBT at 30 degrees C. Strain A66 showed approximately the same desulfurization activity either when incubated at 30 degrees C or at 37 degrees C, while strain A69 showed an increase of desulfurization efficiency (up to 79%) when incubated at 37 degrees C. Strains A66 and A69 were also able to grow using various organosulfur or organonitrogen-compounds as the sole sulfur or nitrogen sources. The biological responses of A66, A69 and IGTS8 strains to a series of mutagens and environmental agents were evaluated, trying to mimic actual circumstances involved in exposure/handling of microorganisms during petroleum biorefining. The results showed that strains A69 and IGTS8 were much more resistant to UVC treatment than A66. The three desulfurization genes (dszA, dszB and dszC) present in strains A66 and A69 were partially characterized. They seem to be located on a plasmid, not only in the strain IGTS8, but also in A66 and A69. PCR amplification was observed using specific primers for dsz genes in all the strains tested; however, no amplification product was observed using primers for carbazole (car) or quinoline (qor) metabolisms. All this information contributes to broaden our knowledge concerning both the desulfurization of DBT and the degradation of organonitrogen compounds within the R. erythropolis species.
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Affiliation(s)
- Silvia C C Santos
- Laboratório de Genética Microbiana, Departamento de Microbiologia Geral, Instituto de Microbiologia Prof. Paulo de Góes (IMPPG), Centro de Ciências da Saúde (CCS), Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ, Brazil
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Chapter 3 Emerging biocatalytic processes. ACTA ACUST UNITED AC 2007. [DOI: 10.1016/s0167-2991(07)80243-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Kirkwood KM, Andersson JT, Fedorak PM, Foght JM, Gray MR. Sulfur from benzothiophene and alkylbenzothiophenes supports growth of Rhodococcus sp. strain JVH1. Biodegradation 2006; 18:541-9. [PMID: 17091342 DOI: 10.1007/s10532-006-9085-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2006] [Accepted: 09/21/2006] [Indexed: 10/23/2022]
Abstract
Rhodococcus sp. strain JVH1 was previously reported to use a number of compounds with aliphatic sulfide bridges as sulfur sources for growth. We have shown that although JVH1 does not use the three-ring thiophenic sulfur compound dibenzothiophene, this strain can use the two-ring compound benzothiophene as its sole sulfur source, resulting in growth of the culture and loss of benzothiophene. Addition of inorganic sulfate to the medium reduced the conversion of benzothiophene, indicating that benzothiophene metabolism is repressed by sulfate and that benzothiophene is therefore used specifically as a sulfur source. JVH1 also used all six isomers of methylbenzothiophene and two dimethylbenzothiophene isomers as sulfur sources for growth. Metabolites identified from benzothiophene and some methylbenzothiophenes were consistent with published pathways for benzothiophene biodesulfurization. Products retaining the sulfur atom were sulfones and sultines, the sultines being formed from phenolic sulfinates under acidic extraction conditions. With 2-methylbenzothiophene, the final desulfurized product was 2-methylbenzofuran, formed by dehydration of 3-(o-hydroxyphenyl) propanone under acidic extraction conditions and indicating an oxygenative desulfination reaction. With 3-methylbenzothiophene, the final desulfurized product was 2-isopropenylphenol, indicating a hydrolytic desulfination reaction. JVH1 is the first microorganism reported to use all six isomers of methylbenzothiophene, as well as some dimethylbenzothiophene isomers, as sole sulfur sources. JVH1 therefore possesses broader sulfur extraction abilities than previously reported, including not only sulfidic compounds but also some thiophenic species.
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Affiliation(s)
- Kathlyn M Kirkwood
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, T6G 2G6, Canada
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Santos SCC, Alviano DS, Alviano CS, Pádula M, Leitão AC, Martins OB, Ribeiro CMS, Sassaki MYM, Matta CPS, Bevilaqua J, Sebastián GV, Seldin L. Characterization of Gordonia sp. strain F.5.25.8 capable of dibenzothiophene desulfurization and carbazole utilization. Appl Microbiol Biotechnol 2006; 71:355-62. [PMID: 16211383 DOI: 10.1007/s00253-005-0154-z] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2005] [Revised: 08/21/2005] [Accepted: 08/29/2005] [Indexed: 12/01/2022]
Abstract
A dibenzothiophene (DBT)-degrading bacterial strain able to utilize carbazole as the only source of nitrogen was identified as Gordonia sp. F.5.25.8 due to its 16S rRNA gene sequence and phenotypic characteristics. Gas chromatography (GC) and GC-mass spectroscopy analyses showed that strain F.5.25.8 transformed DBT into 2-hydroxybiphenyl (2-HBP). This strain was also able to grow using various organic sulfur or nitrogen compounds as the sole sulfur or nitrogen sources. Resting-cell studies indicated that desulfurization occurs either in cell-associated or in cell-free extracts of F.5.25.8. The biological responses of F.5.25.8 to a series of mutagens and environmental agents were also characterized. The results revealed that this strain is highly tolerant to DNA damage and also refractory to induced mutagenesis. Strain F.5.25.8 was also characterized genetically. Results showed that genes involved in desulfurization (dsz) are located in the chromosome, and PCR amplification was observed with primers dszA and dszB designed based on Rhodococcus genes. However, no amplification product was observed with the primer based on dszC.
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Affiliation(s)
- S C C Santos
- Departamento de Microbiologia Geral, Instituto de Microbiologia Prof. Paulo de Góes (IMPPG), Centro de Ciências da Saúde (CCS), Laboratório de Genética Microbiana, Universidade Federal do Rio de Janeiro (UFRJ), Bloco I, Ilha do Fundão, Brazil
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Rashtchi M, Mohebali G, Akbarnejad M, Towfighi J, Rasekh B, Keytash A. Analysis of biodesulfurization of model oil system by the bacterium, strain RIPI-22. Biochem Eng J 2006. [DOI: 10.1016/j.bej.2005.08.034] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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22
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Guobin S, Huaiying Z, Jianmin X, Guo C, Wangliang L, Huizhou L. Biodesulfurization of hydrodesulfurized diesel oil with Pseudomonas delafieldii R-8 from high density culture. Biochem Eng J 2006. [DOI: 10.1016/j.bej.2005.07.003] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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23
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Yu B, Xu P, Shi Q, Ma C. Deep desulfurization of diesel oil and crude oils by a newly isolated Rhodococcus erythropolis strain. Appl Environ Microbiol 2006; 72:54-8. [PMID: 16391024 PMCID: PMC1352184 DOI: 10.1128/aem.72.1.54-58.2006] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2005] [Accepted: 09/23/2005] [Indexed: 11/20/2022] Open
Abstract
The soil-isolated strain XP was identified as Rhodococcus erythropolis. R. erythropolis XP could efficiently desulfurize benzonaphthothiophene, a complicated model sulfur compound that exists in crude oil. The desulfurization product of benzonaphthothiophene was identified as alpha-hydroxy-beta-phenyl-naphthalene. Resting cells could desulfurize diesel oil (total organic sulfur, 259 ppm) after hydrodesulfurization. The sulfur content of diesel oil was reduced by 94.5% by using the resting cell biocatalyst for 24 h at 30 degrees C. Biodesulfurization of crude oils was also investigated. After 72 h of treatment at 30 degrees C, 62.3% of the total sulfur content in Fushun crude oil (initial total sulfur content, 3,210 ppm) and 47.2% of that in Sudanese crude oil (initial total sulfur, 1,237 ppm) were removed. Gas chromatography with pulsed-flame photometric detector analysis was used to evaluate the effect of R. erythropolis XP treatment on the sulfur content in Fushun crude oil, and it was shown that most organic sulfur compounds were eliminated after biodesulfurization.
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Affiliation(s)
- Bo Yu
- State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100, People's Republic of China
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Two-stage process design for the biodesulphurisation of a model diesel by a newly isolated Rhodococcus globerulus DAQ3. Biochem Eng J 2005. [DOI: 10.1016/j.bej.2005.08.012] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Abstract
AIMS To study the desulphurization of dibenzothiophene (DBT), a recalcitrant thiophenic component of fossil fuels, by two bacteria namely Rhodococcus sp. and Arthrobacter sulfureus isolated from oil-contaminated soil/sludge in order to use them for reducing the sulphur content of diesel oil in compliance with environmental regulations. METHODS AND RESULTS The desulphurization pathway of DBT by the two bacteria was determined by gas chromatography (GC) and GC-mass spectrometry. Both organisms were found to produce 2-hydroxy biphenyl (2-HBP), the desulphurized product of DBT. Sulphur contents of culture supernatants of Rhodococcus sp. and A. sulfureus grown with DBT as sole sulphur source were analysed by X-ray fluorescence indicating sulphur levels of 8 and 10 ppm, respectively, as compared with 27 ppm in control. In order to study desulphurization of diesel oils obtained from an oil refinery, resting cell studies were carried out which showed a decrease of about 50% in sulphur content of the oil obtained from the hydrodesulphurization (HDS) unit of the refinery. CONCLUSIONS Rhodococcus sp. and A. sulfureus selectively remove sulphur from DBT to form 2-HBP. Application of these bacteria for desulphurization of diesel showed promising potential for decreasing the sulphur content of diesel oil. SIGNIFICANCE AND IMPACT OF THE STUDY The process of microbial desulphurization described herein can be used for significantly reducing the sulphur content of oil, particularly, after the process of HDS which would help in meeting the regulatory standards for sulphur level in diesel oil.
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Affiliation(s)
- S Labana
- Institute of Microbial Technology, Chandigarh, India
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26
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Ishii Y, Kozaki S, Furuya T, Kino K, Kirimura K. Thermophilic Biodesulfurization of Various Heterocyclic Sulfur Compounds and Crude Straight-Run Light Gas Oil Fraction by a Newly Isolated Strain Mycobacterium phlei WU-0103. Curr Microbiol 2005; 50:63-70. [PMID: 15702256 DOI: 10.1007/s00284-004-4403-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2004] [Accepted: 09/01/2004] [Indexed: 10/25/2022]
Abstract
Various heterocyclic sulfur compounds such as naphtho[2,1-b]thiophene (NTH) and benzo[b]thiophene (BTH) derivatives can be detected in diesel oil, in addition to dibenzothiophene (DBT) derivatives. Mycobacterium phlei WU-0103 was newly isolated as a bacterial strain capable of growing in a medium with NTH as the sulfur source at 50 degrees C. M. phlei WU-0103 could degrade various heterocyclic sulfur compounds, not only NTH and its derivatives but also DBT, BTH, and their derivatives at 45 degrees C. When M. phlei WU-0103 was cultivated with the heterocyclic sulfur compounds such as NTH, NTH 3,3-dioxide, DBT, BTH, and 4,6-dialkylDBTs as sulfur sources, monohydroxy compounds and sulfone compounds corresponding to starting heterocyclic sulfur compounds were detected by gas chromatography-mass spectrometry analysis, suggesting the sulfur-specific desulfurization pathways for heterocyclic sulfur compounds. Moreover, total sulfur content in 12-fold-diluted crude straight-run light gas oil fraction was reduced from 1000 to 475 ppm S, with 52% reduction, by the biodesulfurization treatment at 45 degrees C with growing cells of M. phlei WU-0103. Gas chromatography analysis with a flame photometric detector revealed that most of the resolvable peaks, such as those corresponding to alkylated derivatives of NTH, DBT, and BTH, disappeared after the biodesulfurization treatment. These results indicated that M. phlei WU-0103 may have a good potential as a biocatalyst for practical biodesulfurization of diesel oil.
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Affiliation(s)
- Yoshitaka Ishii
- Department of Applied Chemistry, School of Science and Engineering, Waseda University, Shinjuku-ku, Tokyo 169-8555, Japan.
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Kim YJ, Chang JH, Cho KS, Ryu HW, Chang YK. A physiological study on growth and dibenzothiophene (DBT) desulfurization characteristics of Gordonia sp. CYKS1. KOREAN J CHEM ENG 2004. [DOI: 10.1007/bf02705433] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Chapter 2 Petroleum biorefining: the selective removal of sulfur, nitrogen, and metals. STUDIES IN SURFACE SCIENCE AND CATALYSIS 2004. [DOI: 10.1016/s0167-2991(04)80143-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Abstract
Recent advances in molecular biology have extended our understanding of the metabolic processes related to microbial transformation of petroleum hydrocarbons. The physiological responses of microorganisms to the presence of hydrocarbons, including cell surface alterations and adaptive mechanisms for uptake and efflux of these substrates, have been characterized. New molecular techniques have enhanced our ability to investigate the dynamics of microbial communities in petroleum-impacted ecosystems. By establishing conditions which maximize rates and extents of microbial growth, hydrocarbon access, and transformation, highly accelerated and bioreactor-based petroleum waste degradation processes have been implemented. Biofilters capable of removing and biodegrading volatile petroleum contaminants in air streams with short substrate-microbe contact times (<60 s) are being used effectively. Microbes are being injected into partially spent petroleum reservoirs to enhance oil recovery. However, these microbial processes have not exhibited consistent and effective performance, primarily because of our inability to control conditions in the subsurface environment. Microbes may be exploited to break stable oilfield emulsions to produce pipeline quality oil. There is interest in replacing physical oil desulfurization processes with biodesulfurization methods through promotion of selective sulfur removal without degradation of associated carbon moieties. However, since microbes require an environment containing some water, a two-phase oil-water system must be established to optimize contact between the microbes and the hydrocarbon, and such an emulsion is not easily created with viscous crude oil. This challenge may be circumvented by application of the technology to more refined gasoline and diesel substrates, where aqueous-hydrocarbon emulsions are more easily generated. Molecular approaches are being used to broaden the substrate specificity and increase the rates and extents of desulfurization. Bacterial processes are being commercialized for removal of H(2)S and sulfoxides from petrochemical waste streams. Microbes also have potential for use in removal of nitrogen from crude oil leading to reduced nitric oxide emissions provided that technical problems similar to those experienced in biodesulfurization can be solved. Enzymes are being exploited to produce added-value products from petroleum substrates, and bacterial biosensors are being used to analyze petroleum-contaminated environments.
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Affiliation(s)
- Jonathan D Van Hamme
- Department of Biological Sciences, The University College of the Cariboo, Kamloops, British Columbia V2C 5N3
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Baldi F, Pepi M, Fava F. Growth of Rhodosporidium toruloides strain DBVPG 6662 on dibenzothiophene crystals and orimulsion. Appl Environ Microbiol 2003; 69:4689-96. [PMID: 12902259 PMCID: PMC169080 DOI: 10.1128/aem.69.8.4689-4696.2003] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Strains DBVPG 6662 and DBVPG 6739 of Rhodosporidium toruloides, a basidiomycete yeast, grew on thiosulfate as a sulfur source and glucose (2 g liter(-1) or 10.75 mM) as a carbon source. DBVPG 6662 has a defective sulfate transport system, whereas DBVPG 6739 barely grew on sulfate. They were compared for the ability to use dibenzothiophene (DBT) and related organic sulfur compounds as sulfur sources. In the presence of glucose as a carbon source and DBT as a sulfur source, strain DBVPG 6662 grew better than DBVPG 6739. In the presence of thiosulfate as a sulfur source, the two yeast strains did not use DBT, DBT-sulfone, benzenesulfonic acid, biphenyl, and fluorene. When the two strains were grown in the presence of glucose, strain DBVPG 6662 transformed 27% of the DBT present (10 micro M) at a rate of 0.023 micro mol liter(-1) h(-1) in 36 h. Traces of 2,2'-dihydroxylated biphenyl were transiently accumulated under these conditions. When the same strain was grown on glucose in the presence of a higher concentration of DBT (0.5 g liter(-1)), mainly in an insoluble form, the whole surface of the DBT crystals was colonized by a thick mycelium. This adherent structure was imaged by confocal microscopy with fluorescent concanavalin A, a lectin that specifically binds glucose and mannose residues. When DBVPG 6662 was grown on glucose in the presence of a commercial emulsion of bitumen, i.e., orimulsion, 68% of the benzo- and dibenzothiophenes and DBTs was removed after 15 days of incubation. The fungus adhered by hyphae to orimulsion droplets. When cultivated in the presence of commercial emulsifier-free fuel oil containing alkylated benzothiophenes and DBTs and having a composition similar to that of orimulsion, strain DBVPG 6662 removed only 11% of the total organic sulfur that occurs in the medium and did not adhere to the oil droplets. These results indicate that strain DBVPG 6662 is able to utilize the organic sulfur of DBT and a large variety of thiophenic compounds that occur extensively in commercial fuel oils by physically adhering to the organic sulfur source.
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Affiliation(s)
- Franco Baldi
- Department of Environmental Sciences, Cà Foscari University, S. Marta, Dorsoduro 2137I-30121 Venice, Italy.
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Noh SL, Choi JM, An YJ, Park SS, Cho KS. Anaerobic biodegradation of toluene coupled to sulfate reduction in oil-contaminated soils: optimum environmental conditions for field applications. JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH. PART A, TOXIC/HAZARDOUS SUBSTANCES & ENVIRONMENTAL ENGINEERING 2003; 38:1087-1097. [PMID: 12774911 DOI: 10.1081/ese-120019866] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Degradation characteristics of toluene in enrichment culture were investigated in soil microcosms study and the optimum environmental conditions for anaerobic degradation of toluene coupled with sulfate reduction were determined for field site applications. Anaerobic sulfate-reducing bacteria were enriched from oil contaminated soil samples with toluene. Enriched consortia degraded toluene with sulfate as a terminal electron acceptor. The average degradation rate of toluene in enriched consortia ranged from 0.08 to 0.1 micromol g(-1) day(-1). Toluene degradation under sulfate-reducing condition was inhibited in the presence of molybdate alone or together with nitrate or fumarate, indicating that toluene is degraded directly by sulfate-reducing bacteria. Effects of initial toluene concentration, pH, temperature, and other hydrocarbons on toluene degradation were investigated. There is a trend of increasing rate of toluene degradation with increasing the initial mass up to 94 micromol of toluene. Toluene degradation did not affected by the presence of ethylbenzene and xylene, as a while, toluene was degraded in a slower rate in the presence of benzene. The sulfate-reducing bacteria in the enriched culture showed higher microbial activity at neutral (pH 6-8) and medium temperature (30-37 degrees C) environments.
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Affiliation(s)
- Seung-Lim Noh
- Department of Environmental Science and Engineering, Ewha Womans University, Seoul, Korea
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Effects of aqueous media on microbial removal of sulfur from dibenzothiophene in the presence of hydrocarbons. CHINESE SCIENCE BULLETIN-CHINESE 2003. [DOI: 10.1007/bf03183223] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Castorena G, Suárez C, Valdez I, Amador G, Fernández L, Le Borgne S. Sulfur-selective desulfurization of dibenzothiophene and diesel oil by newly isolated Rhodococcus sp. strains. FEMS Microbiol Lett 2002; 215:157-61. [PMID: 12393216 DOI: 10.1111/j.1574-6968.2002.tb11385.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
New desulfurizing bacteria able to convert dibenzothiophene into 2-hydroxybiphenyl and sulfate were isolated from contaminated soils collected in Mexican refineries. Random amplified polymorphic DNA analysis showed they were different from previously reported Rhodococcus erythropolis desulfurizing strains. According to 16S rRNA gene sequencing and fatty acid analyses, these new isolates belonged to the genus Rhodococcus. These strains could desulfurize 4,6-dimethyldibenzothiophene which is one of the most difficult dibenzothiophene derivatives to remove by hydrodesulfurization. A deeply hydrodesulfurized diesel oil containing significant amounts of 4,6-dimethyldibenzothiophene was treated with Rhodococcus sp. IMP-S02 cells. Up to 60% of the total sulfur was removed and all the 4,6-dimethyldibenzothiophene disappeared as a result of this treatment.
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Affiliation(s)
- Gladys Castorena
- Instituto Mexicano del Petróleo, Programa de Investigación y Desarrollo en Biotecnologi;a del Petróleo, Eje Central Lázaro Cárdenas 152, Col. San Bartolo Atepehuacan, 07730, Mexico City, DF, Mexico.
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Grossman MJ, Lee MK, Prince RC, Minak-Bernero V, George GN, Pickering IJ. Deep desulfurization of extensively hydrodesulfurized middle distillate oil by Rhodococcus sp. strain ECRD-1. Appl Environ Microbiol 2001; 67:1949-52. [PMID: 11282654 PMCID: PMC92818 DOI: 10.1128/aem.67.4.1949-1952.2001] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Dibenzothiophene (DBT), and in particular substituted DBTs, are resistant to hydrodesulfurization (HDS) and can persist in fuels even after aggressive HDS treatment. Treatment by Rhodococcus sp. strain ECRD-1 of a middle distillate oil whose sulfur content was virtually all substituted DBTs produced extensive desulfurization and a sulfur level of 56 ppm.
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Affiliation(s)
- M J Grossman
- ExxonMobil Research and Engineering Co., Route 22 East, Annandale, New Jersey 08801, USA.
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Chang JH, Chang YK, Ryu HW, Chang HN. Desulfurization of light gas oil in immobilized-cell systems of Gordona sp. CYKS1 and Nocardia sp. CYKS2. FEMS Microbiol Lett 2000; 182:309-12. [PMID: 10620684 DOI: 10.1111/j.1574-6968.2000.tb08913.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Desulfurizations of a model oil (hexadecane containing dibenzothiophene (DBT)) and a diesel oil by immobilized DBT-desulfurizing bacterial strains, Gordona sp. CYKS1 and Nocardia sp. CYKS2, were carried out. Celite bead was used as a biosupport for cell immobilization. Seven-eight cycles of repeated-batch desulfurization were conducted for each strain. Each batch reaction was carried out for 24 h. In the case of model oil treatment with strain CYKS1, about 4.0 mM of DBT in hexadecane (0.13 g sulfur l(oil)(-1)) was desulfurized during the first batch, while 0.25 g sulfur l(oil)(-1) during the final eighth batch. The mean desulfurization rate increased from 0.24 for the first batch to 0.48 mg sulfur l(dispersion)(-1) h(-1) for the final batch. The sulfur content in the light gas oil was decreased from 3 to 2.1 g l(oil)(-1) by strain CYKS1 in the first batch. The mean desulfurization rate was 1.81 mg sulfur l(dispersion)(-1) h(-1), which decreased slightly when the batch reaction was repeated. No significant changes in desulfurization rate were observed with strain CYKS2 when the batch reaction was repeated. When the immobilized cells were stored at 4 degrees C in 0.1 M phosphate buffer (pH 7.0) for 10 days, the residual desulfurization activity was about 50 approximately 70% of the initial value.
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Affiliation(s)
- J H Chang
- Department of Chemical Engineering and BioProcess Engineering Research Center, Korea Advanced Institute of Science and Technology, 373-1, Kusong-dong, Yusong-gu, Taejon, South Korea
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Abstract
Microbial sulfur-specific transformations have been identified that selectively desulfurize organic sulfur compounds in fossil fuels. Recent discoveries related to biodesulfurization mechanisms may lead to commercial applications of biodesulfurization through engineering recombinant strains for over-expression of biodesulfurization genes, removal of end product repression, and/or by combining relevant industrial and environmental traits with improvements in bioprocess design.
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Affiliation(s)
- B L McFarland
- MicroBioTech Consulting, 1143 Halifax Avenue, Davis, CA 95616-2718, USA.
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