“Man can believe the impossible, but can never believe the improbable” - Oscar Wilde (Irish Poet, Novelist, Dramatist and Critic, 1854-1900)
It is nearly impossible to find quality technical articles for free these days … nearly, but not entirely. Here are 16 items I found recently. Browse through and pick out the ones you like.
They all were found by searching and browsing (lots of browsing!) Google® Scholar and NDLTD - Networked Digital Library of Theses and Dissertations (www.ndltd.org)
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Journal of Bioremediation & Biodegradation, Volume 1• Issue 3•1000112 (2010)
Pankaj Kumar Arora (1), Alok Srivastava (2)* and Vijay Pal Singh (2)
1 Environmental Biotechnology, Microbial Type Culture Collection and Gene Bank (MTCC), Institute of Microbial Technology, Sector-39A, Chandigarh-160036, India
2 Department of Plant Science, Faculty of Applied Sciences, M.J.P. Rohilkhand University, Bareilly -243006, India
1:112. doi:10.4172/2155-6199.1000112
Abstract
Monooxygenases act as biocatalysts in bioremediation process and synthetic chemistry due to their highly regioselectivity and sterioselectivity on wide range of substrates. They are involved in the process of desulfurization, dehalogenation, denitrification, ammonification, hydroxylation, biotransformation and biodegradation of various aromatic and aliphatic compounds. In the recent years, the practical applications of monooxygenases have been improved using the approaches of directed evolution, meta-genomics and bioinformatics. This review is focused on current applications of monooxygenses especially in biodegradation and biotransformation of aromatic compounds.
Monooxygenases Involved in Biodesulfurization of Dibenzothiophene
Sulphur containing organic compounds such as dibenzothiophene (DBT) are present in the fossil fuels. On combustion of these fossil fuels, sulphur dioxide is released into the environment and causes air pollution. The complete removal of sulphur from these compounds is not possible by conventional physical and chemical methods. Biodesulfurization, therefore, is a process that completely removes sulphur from these organic compounds. Biodesulfurization of DBT is well characterized in Rhodococcus erythropolis IGTS8 [33]. Two flavin dependent monooxygenases, DBT monooxygenase (DszC) and DBT sulfone monooxygenases (DszA) are involved in the initial steps of the biodesulfurization. DBT monooxygenase (EC 1.14.13.-) converts DBT to DBT sulphoxide which is further converted to DBT sulphone by same enzyme (Figure 3a and 3b). DBT sulfone monooxygenase (EC 1.14.13.-) converts DBT sulfone to 2’-hydroxybiphenyl 2-sulfinate (HBPS) (Figure 3c). Both of the monooxygenases require another enzyme flavin reductase (DszD) for their activities. One more enzyme HBPS desulfinase (DszB) is also involved in the final step of biodesulfurization and converts HBPS to hydroxybiphenyl (HBP) and sulphate (Figure 3d). In R. erythropolis, enzymes DszA, DszB and DszC are encoded by plasmid located dsz operon and another enzyme DszD is considered as genome encoded [34, 35]. The desulfurization genes was conserved among Rhodococcus species [36]. Several strains of R. erythropolis, i.e., SY1, D-1, Ni-36, Ni-43, and QIA-22 exhibited same DBT-desulfurizing reaction as reported in Rhodococcus erythropolis IGTS8 [37-40].
Although the biochemistry, genetics and physiology of desulphurization have been extensively studied in Rhodococcus sp., the desulfurizing genes (dszABC) have also been identified in other mesophilc bacteria [41-43] as well as thermophilc bacteria.
Free Full Text Source: http://www.omicsonline.org/2155-6199/2155-6199-1-112.pdf
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Journal of Scientific & Industrial Research, Vol. 69, July 2010, pp. 543-547
Nandi, Somnath
Abstract:
This study presents simulation of an indigenously designed airlift reactor (vol. 43.746 dm3) to lower down sulfur content ofhydrodesulfurized diesel from 500 ppm (mg/dm3) to ultra-low level using Rhodococcus sp. as microbial biocatalyst. A detailedmodeling using TSM (tanks in series model) is proposed to demonstrate efficacy of airlift reactor for biodesulfurization.
Free Full Text Source: http://nopr.niscair.res.in/handle/123456789/9858
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Middle-East Journal of Scientific Research 7 (1): 22-29, 2011
Maryam Khavarpour et al., Biotechnology Research Center, Faculty of Chemical Engineering, Noushirvani University of Technology, Babol, Iran
Abstract
The present study focused on evaluatin of various kinetic models for hydrogen sulfur removal by means of active microorganisms. The microorganisms used for the removal of hydrogen sulfide were isolated from a local hot spring. The experiments were conducted with natural gas at initial pressures of 1 to 1.8atm. Several kinetic models such as: Andrew, Contois, Logistic, Monod, Moser, Tessier and Verhulst models in a batch culture were used to describe the microbial growth and substrate utilization. At low pressure (1 atm) the bacterial behavior were substrate related and growth and dependent, thus, Monod and Tessier models were unable to explain the microbial behavior. At gas pressure of 1.2 atm, maximum cell dry weight of 3.136 and 1.724g.1-t were obtained with Logistic and Verhulst models, respectively. The obtained regression values for Logistic model were reasonably acceptable for all initial gas pressures. As the gas pressure was increased to 1.8 atm, the inhibition coefficient may be dominated in growth kinetic. Andrew's equation was also able to predict inhibition constant.
Free Full Text Source: http://www.idosi.org/mejsr/mejsr7(1)11/5.pdf
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International Journal of Microbiology, Volume 2010, Article ID 319527, 9 pages
Review Article
Sofiya N. Parshina (1) Jan Sipma (2) AnneMeint Henstra (3) and Alfons J.M. Stams (3)
1 Laboratory of Microbiology of Anthropogenic Environments, Winogradsky Institute of Microbiology, Russian Academy of Sciences, 117312, prosp. 60 let Oktyabrya, 7, b.2, Moscow, Russia
2 Laboratory of Chemical and Environmental Engineering (LEQUIA), University of Girona, 17071 Girona, Spain
3 Laboratory of Microbiology, Wageningen University, 6703 HB, Wageningen, The Netherlands
Abstract
Several strains of Gram-negative and Gram-positive sulphate-reducing bacteria (SRB) are able to use carbon monoxide (CO) as a carbon source and electron donor for biological sulphate reduction. These strains exhibit variable resistance to CO toxicity. The most resistant SRB can grow and use CO as an electron donor at concentrations up to 100%, whereas others are already severely inhibited at CO concentrations as low as 1-2%. Here, the utilization, inhibition characteristics, and enzymology of CO metabolism as well as the current state of genomics of CO-oxidizing SRB are reviewed. Carboxydotrophic sulphate-reducing bacteria can be applied for biological sulphate reduction with synthesis gas (a mixture of hydrogen and carbon monoxide) as an electron donor.
1. Introduction
Sulphate reducers are anaerobic microorganisms that are able to use sulphate as a terminal electron acceptor [1]. They are widespread in anoxic habitats [2] and can use numerous substrates as electron donor for growth. These include sugars [3, 4], amino acids [5, 6], hydrogen [7], and one-carbon compounds, such as methanol [8–11], carbon monoxide [12–14], and methanethiol [15]. Even alkanes [16–19], alkenes [20], and short-chain alkanes [21], as well as aniline [22], benzoate, phenol, aromatic hydrocarbons [23– 25], and phosphite [26] are used as electron donor. Sulphate-reducing bacteria play an important role in biodesulfurization processes. Industries that use sulphuric acid, sulphate-rich feedstocks, or reduced sulphur compounds generate wastewaters rich in sulphate [27]. Sulphate is removed from wastewater by the combined activity of SRB that generate sulphide and the subsequent partial oxidation of sulphide to insoluble elemental sulphur by sulphide oxidizing bacteria [28]. Biotechnological applications of sulphate reduction further include SOx abatement from the flue gas of coal fueled power plants [27] and treatment of sulphate-rich, heavy metal contaminated wastewaters. Heavy metals such as Cu, Zn, Cd, Pb, Ni, and Fe can be removed from waste streams by precipitation with biogenic sulfide. Because of differences in solubility of products, the metals can be selectively precipitated, which enables their recovery and reuse as demonstrated at full-scale for a zinc smelting plant [29].
If sulphate-rich wastewaters contain no or insufficient amounts of suitable electron and carbon donors for sulphate reduction, external addition becomes a prerequisite. Examples of such wastewaters are waste streams generated in galvanic processes, in the detoxification of metal-contaminated soils, in the mining of heavy metals and coal, and in flue gas desulphurization.
Free Full Text Source: http://downloads.hindawi.com/journals/ijmb/2010/319527.pdf
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SCIENCE CHINA Chemistry, Volume 53, Number 7, 1470-1475
HuiZhou Liu, XiangFeng Liang, LiangRong Yang and JiaYong Chen
Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
Abstract
Process intensification is one of the most significant trends in current chemical engineering and process industries. In recent years, the desire to become more “green” in processing has always been tied to the requirement of being profitable. This review discusses the challenges of process engineering and summarizes the key role of fundamentals for green process intensification. green chemistry, process intensification
3.3.2 Biodesulfurization and adsorption desulfurization
Hydrodesulfurization (HDS) is the commonly used method for reducing the sulfur content. It is effective for removing inorganic sulfur and simple organic sulfur compounds. However, it is difficult to remove heterocyclic sulfur compounds. By contrast, biodesulfurization is a promising technology to remove these recalcitrant compounds more selectively and cost-effectively [22, 23]. Dibenzothiophene (DBT) has been used as a model polyaromatic sulfur heterocyclic compound for the isolation and characterization of bacteria capable of transforming organosulfur compounds. The finding of bacteria that use a sulfur-selective oxidative pathway (4S pathway) to remove sulfur from organic sulfur compounds is a breakthrough of biodesulfurization, for this method preserves the fuel value of the desulfurized product. Biodesulfurization will be an efficient way to realize the green chemistry in the 21st century. Biodesulfurization could be not only performed alone but also integrated with other kinds of desulfurization processes. This provides a new method for deep desulfurization and increases its applicability. Adsorption desulfurization is a process that utilizes adsorbents to adsorb sulfur compounds in the fuel at ambient temperature and normal pressure. The economic benefit of adsorption desulfurization is attractive if the capacity of the sulfur adsorbent could be kept for a long time, for example, one year. Compared with the HDS, the cost of adsorption desulfurization decreases about more than a half. Biodesulfurization has the disadvantage of long reaction time and low volume of samples. The main obstacle for the application of adsorption desulfurization is the regeneration and recycle of the adsorbent. Integration of adsorption desulfurization and biodesulfurization could result in the lower sulfur content oil (lower than 30 ppm) by removing the organic sulfur compounds, for HDS is more difficult to remove. Moreover, the integrated desulfurization process has the advantage of low energy consumption, no production of poisonous waste, and most significantly, the reuse of the adsorbents. This novel integration technique will arouse much interest in desulfurization (Figure 4).
Free Full Text Source: http://www.springerlink.com/content/b032g5105n11hj48/
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Extremophiles (2010) 14:475–481
D. Boniek
Graduate Program in Environmental Engineering, Institute of Biological and Exact Sciences, Federal University of Ouro Preto, Ouro Preto, MG, Brazil
V. S. Pylro
Graduate Program in Agricultural Microbiology, Microbiology Department, Federal University of Vic¸osa, Vic¸osa, MG, Brazil
D. Figueiredo
G. F. Duarte
Biodiversity and Microbial Ecology Laboratory, Biological Sciences Department, Institute of Biological and Exact Sciences, Federal University of Ouro Preto, Ouro Preto, MG 35400-000, Brazil
Introduction
The release of sulphur dioxide into the atmosphere from the combustion of fossil fuels is a serious environmental concern because it contributes to air pollution and is a major cause of acid rain (Tanaka et al. 2002). Thus, it is necessary that sulphur oxides be removed from fossil fuels before, during and after combustion (Ohshiro and Izumi 1999). Most refineries use the conventional technique of hydrodesulphurisation (HDS), which removes sulphur from diesel fuel at high temperatures (200–450_C) and pressures (150–250 psi) in the presence of an inorganic catalyst (Orr 1978; Speight 1980; Izumi et al. 1994). However, this technique requires much energy and produces a high level of pollution (Ohshiro and Izumi 1999). Dibenzothiophene (DBT) and its derivatives are persistent and ubiquitous heterocyclic environmental pollutants. The development of catalysts capable of desulphurising HDS-resistant thiophenes is necessary for further desulphurisation of petroleum fractions (Chen et al. 2008).
The biological desulphurisation of DBT can be carried out by oxidative or reductive pathways that release sulphur as sulphate or sulphide, respectively. Several studies have investigated the development of aerobic microbial desulphurisation pathways. Some bacteria can desulphurise DBT to 2-hydroxybiphenyl (2-HBP) through the sulphur-specific degradation pathway (4S pathway) without destroying the hydrocarbon skeleton (Olson et al. 1993; Nekodzuka et al. 1997; Chang et al. 2000), and several DBT-desulphurising bacterial species have been reported (Omori et al. 1992; Chang et al. 1998).
Antarctica is one of the largest remaining areas on the planet that contributes to the maintenance of the global climate equilibrium. However, in the last century, the human activity in Antarctica relied heavily on fossil fuels for transportation and the generation of power. As in other regions of the world, this activity has led to petroleum hydrocarbon contamination of soils (Aislabie et al. 2004). Microorganisms are the dominant biomass component of Antarctic ecosystems (Wynn-Williams 1996; Pointing et al. 2009). The harsh conditions of this habitat are fundamental to selecting those organisms able to survive in such an extreme habitat and able to support the relatively simple ecosystems. Hydrocarbon spills may result in enrichment of culturable heterotrophic bacteria and hydrocarbon-degrading microorganisms (Aislabie et al. 2004) and the numbers of culturable heterotrophs are typically 1–2 orders of magnitude higher in contaminated soil than in control soil.
Hydrocarbon-degrading bacteria can be applied in the biodesulphurisation of DBT process and they have been isolated from contaminated Antarctic soils (reviewed in Aislabie et al. 2004). These bacteria have been assigned to a number of genera including Acinetobacter, Rhodococcus, Pseudomonas and Sphingomonas. In this study we analysed the composition of the culturable bacterial community in soil samples from Antarctica, focusing on bacteria capable of desulphurisation, through the use of conventional microbiological methodologies and molecular techniques.
Free Full Text Source: http://www.springerlink.com/content/dhl6715l11j715pu
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INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCES Volume 1, No 7, 2011
Kumar Arun 1 , Munjal Ashok 1 , Sawhney Rajesh 2
1Department
of Bioscience and Biotechnology, Banasthali Vidyapith, Banasthali, Rajasthan
(India)304022
2Department
of Microbiology, Bhojia Institute of Life Sciences, Budh, Baddi. Distt.
Solan,Himachal Pradesh (India)173205
ABSTRACT
Crude oil, a dark sticky liquid, is a complex mixture of varying molecular weight which is used for the preparation of petroleum products. Crude oil contains more than 30 parent polyaromatic hydrocarbons (PAHs). The U.S.EPA has designated 16 PAH compounds (naphthalene, acenaphthylene, acenaphthene, fluorene, phenenthrene, anthracene, fluoranthene, pyrene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenz[a, h]anthracene, benzo[g, h, i]perylene, and indeno[1,2,3cd] pyrene) as priority pollutants. PAHs are one of the most widespread organic pollutants and potentially health hazard. Besides other environmental components, they are also found in foods (cereals, oils, fats, vegetables, cooked meat). They are carcinogenic , mutagenic , and teratogenic . Thus, key focus is to eliminate these hazardous pollutants from the environment. The present review highlights the presence of various PAHs in the crude oil, key metabolic pathway for the degradation and the associated microbial degraders. The current approach to bioremediation uses various bacterial and fungal genera under aerobic or anaerobic conditions to directly target the specific PAH. However, there is need to explore newer approaches to design an efficient, effective and ecofriendly bioremediation tool. The dearomatization of crude oil might be a useful comprehensive approach and one shot solution to multiple PAH population.
Free Full Text Source: http://ipublishing.co.in/jesvol1no12010/EIJES2092.pdf
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Journal of American Science. 2010;6(11):343-356
Nour Sh. El-Gendy1*, Yasser M. Moustafa1, Salem A. Habib2, Sherif Ali1
1Egyptian Petroleum Research Institute, Cairo, P.O. 11727, Egypt.
2Mansoura University, Faculty of Science, Damietta, Egypt.
Abstract: Corynebacterium variabilis sp. Sh42 is used to investigate the biodegradation potentials and metabolic pathways of different poly aromatic compounds (PACs) in batch flasks. Effects of PACs size, molecular weight, alkylation and their presence individually or in mixture on biodegradation potentials of Sh42 were studied; Naphthalene (Nap) as a model compound for di-aromatic ring; Antheracene (Ant) and Phenantherene (Phe) as model compounds for tri-aromatic ring; while Pyrene (Pyr) as a model compound for four-aromatic ring compounds were used as representatives for different PAHs. Dibenzothiophene (DBT), 4-methyldibenzothiophene (4-MDBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) were taken as representative models for PASHs compounds. While, 2-hydroxybiphenyl (2-HBP) and 2, 2'-bihydroxybiphenyl (2, 2'-BHBP) were taken as models for phenolic compounds. The experimental results show that biodegradation rate decrease with increase ring size, alkylation’s group within homologous series and Sh42 has the highest capability to biodegradation of toxic phenolic compounds either in single (BD% ˜ 90%) or mixed substrates cultures (BD% ˜ 48%). To ensure detoxification and mineralization of these toxic PACs; metabolic pathways of representative model compounds (Pyr, DBT and 2,2'-BHBP) were elucidated by GC/MS analysis which confirmed that, Sh42 completely metabolized all representative compounds to CO2 and H2O.
Free Full Text Source: http://www.jofamericanscience.org/journals/am-sci/am0611/41_3163am0611_343_356.pdf
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J Pet Environ Biotechnol 2:107 (2011)
Gamil A. Amin
Taif University, Taif, Saudi Arabia
Abstract
A single vertical rotating immobilized cell reactor (VRICR) with the bacterium R. erythropolis, as a biocatalyst, was developed and used for investigation of biodesulfurization process with its two successive stages of cell growth and desulfurization activity. With a rotation speed of 15 rpm and oxygen transfer rate of 90 mM O2.l-1.h-1, immobilized cell concentration of up to 70.0 g.l-1 was achieved during the first stage and further used, in the second, to carry out a stable continuous desulfurization of model oil (dibenzothiophene in hexadecane). A steady state with specific desulfurization rate as high as 167 mM 2HBP.Kg-1.h-1 and sulfur removal efficiency of 100% were maintained for more than 120 h. The proposed integrated biodesulfurization process utilizing the VRICR has the potential to lower operating costs and support possibilities of commercial application at the expense of Hydrodesulfurization process currently employed
Free Full Text Source: http://www.omicsonline.org/2157-7463/2157-7463-2-107.php
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African Journal of Biotechnology, Vol 8, No 12 (2009)
C Montiel, R Quintero, J Aburto
Abstract
This paper comes out from the need to provide a general overview of the current biotechnology situation and its future impact on the petroleum industry. This important industrial sector already encounters challenges as the decreasing oil reserves, the fluctuating oil prices, the increasing demand of petroleum, fuels and petrochemicals and finally more strict environmental regulations. These challenges will persist and strengthen in the following years. Biotechnology has come a long way since the 1950's and today impacts different industrial sectors such as food, pharmaceutics, medicine, agriculture, textile, etc. Because of good experiences of the above industries, the petroleum industry interests is now in biotechnology as an alternative technology to resolve the challenges and needs of this worldwide important sector. We described throughout the paper the main factors that drive or restrain research and development (R&D) in biological processes applied to petroleum industry. Moreover, we identified several challenges and opportunities, where R&D in petroleum biotechnology plays an important role to surmount the industrial needs during the following years
Free Full Text Source: http://www.ajol.info/index.php/ajb/article/view/60810
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Appl Microbiol Biotechnol (2010) 85:615–624
J.-D. Zhang : A.-T. Li : Y. Yang : J.-H. Xu
State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, People’s Republic of China
J.-H. Xu (*)
Laboratory of Biocatalysis and Bioprocessing, State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, People’s Republic of China
Introduction
Rhodococcus species are ideal candidates which have been proven of immense use for a wide range of biotransformation, such as steroid modification, enantioselective synthesis, and the production of amides fromnitriles (Warhurst and Fewson 1994; Larkin et al. 1998, 2005; Bell et al. 1998). They have been used to specifically remove sulfur from coal and oil after hydrodesulfurization that releases recalcitrant Sheterocyclic compounds such as benzothiophene, dibenzothiopene, and 4,6-dimethyldibenzothiophene (Prince and Grossman 2003; Tanaka et al. 2002). A common feature of the aerobic Rhodococcus genus is the presence of many types of monooxygenases and dioxygenases. For instance, a heme-containing cytochrome P450 enzyme in the degradation of substituted aromatics (Karlson et al. 1993), thiocarbamates, atrazine (Nagy et al. 1995), and ethyl tertiary butyl ether (Chauvaux et al. 2001) have been demonstrated. Recently, an explosive-degrading P450 system XplA/B was identified from Rhodococcus rhodochrous 11Y, and its oxidizing activity was detected towards both methyl tolyl and methyl phenyl sulfides (Seth-Smith et al. 2002; Jackson et al. 2007). At present, at least 16 P450 monooxygenases belonging to different subfamilies including four members from the CYP116 subfamily have been reported in Rhodococcus strains (David Nelson’s homepage, http://drnelson. utmem.edu/CytochromeP450.html). For dioxygenases, a naphthalene dioxygenase (Nar Aa, Ab) from Rhodococcus sp. NCIMB 12038 has been elucidated (Malik et al. 2002). A similar crystal structure of the terminal oxygenase components (BphA1A2) of the biphenyl dioxygenase from Rhodococcus sp. RHA1 has also been determined (Furusawa et al. 2004).
Free Full Text Source: http://www.springerlink.com/content/57u263n2583085m1/
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Chemosphere, Volume 82, Issue 4, January 2011, Pages 489-494
Review
Xiaolei Zhang (a), Song Yan (a), R.D. Tyagi (a), and R.Y. Surampalli (b)
a INRS Eau, Terre et Environnement, 490, rue de la Couronne, Québec, Canada G1K 9A9
b US Environmental Protection Agency, P.O. Box 17-2141, Kansas City, KS 66117, USA
Abstract
Nanotechnology has attracted a great interest in recent years due to its expected impact on many areas such as energy, medicine, electronics, and space industries. This review provides the state-of-art knowledge on the synthesis of nanoparticles by microorganisms including bacteria, fungi, actinomycetes, and yeast, and their effect on microbiological processes. The available microbes and their predicted nanoparticle biosynthesis mechanism, the conditions to control the size/shape and monodispersity of particles, and microbiological reaction rate enhancement using nanoparticles as catalysts are presented. The current limitations and future scope for specific research are also discussed.
3. Application of nanoparticles in enhancing the microbiological reaction rates
Nanoparticles have been widely used to improve various reactions as reductants and/or catalysts in chemistry field due to their high specific surface areas and characters ([Ivanov et al., 2000], [Kopinke et al., 2003], [Hildebrand et al., 2008] and [Nezahat et al., 2009]). However, so far, very limited studies have been reported on nanoparticle effect on the microbiological reaction rates. Nanosized palladium particles formed on the cell wall or inside the periplasmic of Shewanella oneidensis were found to have the ability to encourage dehalogenate polychlorinated biphenyl (PCB) reduction (De Windt et al., 2005). It was observed that more than 90% decrease of PCB 21 (2,3,4-chloro biphenyl) coupled to formation of its dechlorination products PCB 5 (2,3-chloro biphenyl) and PCB 1 (2-chloro biphenyl) was obtained at a concentration of 1 mg L-1 within 5 h at 28 °C. It is due to the fact that palladium Pd(0) nanoparticles could combine with hydroxyl radicals by providing electron donors such as hydrogen, acetate and formate. When S. oneidensis cells deposited Pd(0) nanoparticles charged with hydroxyl radical meet chlorinated compounds, the hydroxyl radical bonded on the Pd(0) would catalytically react with PCB, consequently, the chlorine molecule would be removed from the chlorinated compounds. The results exhibited that nanoparticles extensively increased the catalytic activity of Pd(0). The same amount of Pd(0), nanoparticle Pd(0) has 9-fold higher catalytic activity compared to commercial Pd(0) powder on the PCB removal. Magnetic nanoparticles have also been used to improve the microbiological reaction rates. In fact, the magnetic ones are utilized due to not only their catalytic function but also well dispersible ability. Shan et al. (2005) made use of the coated microbial cells of Pseudomonas delafieldii with magnetic Fe3O4 nanoparticles to fulfill desulfurization of dibenzothiophene. The high surface energies of nanoparticles resulted in their strong adsorption on the cells. An external magnetic field application ensured the well diffusion of cells in the solution even without mixing and enhanced the possibility to collect cells for reuse. The results showed that the desulfurization efficiencies of P. delafieldii were not reduced and the cells could be reused several times.
Free Full Text Source: http://www.sciencedirect.com/science/article/pii/S0045653510011665
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International Journal of Biotechnology and Biochemistry, Volume 6 Number 2 (2010) pp. 219–229
Increasing of Biodesulfurization Activity of Newly Recombinant Pseudomonas Aeruginosa ATCC 9027 by Cloning the Flavin Reductase Gene
Jamshid Raheb¹*, Mohammad Javad Hajipour¹,² and Babak Memari¹
1 National Institute of Genetic Engineering and Biotechnology (NIGEB), Karaj-Tehran highway, Pajoohesh Blvd. P.O.Box.14155-6343
2 Department of Biological Science Imam Hossein university, Tehran - Iran.
Abstract
Sulfur emission through fossil fuel combustion is a major cause of acid rainand air pollution. The main aim of running of this research was increasing thebiodesulfurization activity of recombinant P. aeruginosa ATCC9027 bycloning of flavin reductase gene. There are four gene dszA,B,C,D which areinvolved in desulfurization pathway (4s) and allowed release of sulfur afterfour enzymatic steps. In this pathway Monooxygenases DszC and DszAenzymes require free FMNH2 which provided by DszD enzyme. In the presentstudy the pVLT31 vector harboring flavin-oxidoreductase gene (dszD) wastransferred into the recombinant P. aeruginosa ATCC9027 which containeddszABC gene in its chromosome stably. We found that the biodesulfurizationacivity of the recombinant P. aeruginosa ATCC9027 enhanced when thesefour genes co-expressed. The data obtained here confirmed by biochemicalquantitative Gibbs assay.
Introduction
The present of sulfur in coal and petroleum contributes to corrosion of production andrefining equipments. Burning this high sulfur production emit sulfur oxides toatmosphere and is a major cause of acid rain and air pollution [1, 2]. Dibenzothiophen(DBT) is generally accepted as the model compound for organic sulfur-containingfossil fuel component [3, 4]. Hydrodesulfurization is current chemical method for sulfur removal which converts organic sulfur in the feed higher hydrogen pressure andtemperature giving greater sulfur removal [5, 6, 7]. Biodesulfurization (BDS) is aprocess which is cheap and can operate with the high selectivity needed for theeconomic desulfurization of fossil fuel [8, 9, 10]. Rhodococcus erythropolis IGTS8 isable to extract sulfur from different organosulfur compounds. This bacterium have thegenes and enzymes responsible for removing sulfur from dibenzothiophen to yield 2-hydroxybiphenyl as the final product, meaning that there is no degradation of thecarbon-carbon bonds in the dibenzothiophen molecule. Desulfurization of DBT isconsidered a proceed via the 4S pathway, that is oxidation of DBT to sulfone by DszCand subsequent oxygenation by DszA occurs to yield 2-(2-Hydroxyphenyl)benzensulfinat (HPBS) by DszA. HPBS is converted to 2-hydroxybiphenyl (2-HBP)by DszB. DszD is flavin oxidoreductase and absoloutely required in the reactioncatalysed by DszC and DszA enzymes. DszD enzyme catalysed the reduction offlavins, such as flavin mono nucleotid, FAD and riboflavin by NADH and/or NADPHto form reduced flavin The first two Enzyme in this pathway (4S) belong to thenonflavin containing "Two-Componenet monooxygenase" family which require freeFMNH2 for activity-this is provided in the recombinant Pseudomonas by four protein[11, 12, 13, 14]. The 4S pathway is potentially useful for removing the sulfur fromcompound in petroleum and or coal. Unfortunately this strain is among those bacteriawith a low tolerance towards solvents and is therefore unable to function optimally inthe high concentration of hydrocarbons currently used in petrochemical process [15,16, 17]. In this study the pVLT31 vector harboring flavin-oxidoreductase gene (dszD)was transferred in to the aforementioned recombinant strain and measured 2-HBPproduction of this recombinant strain by qualitative and quantitative Gibbs assaywhen these four genes co-expressed.
Free Full Text Source: http://74.125.155.132/scholar?q=cache:ea0LNam0gcgJ:scholar.google.com/+desulfurization&hl=en&as_sdt=0,11&as_ylo=2010&as_yhi=2011
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Korean Journal of Chemical Engineering, Volume 27, Number 2, 624-631
Kyu-Sung Kim, Sun Hee Park, Ki Tae Park, Byung-Hee Chun, and Sung Hyun Kim†
Department of Chemical and Biological Engineering, Korea University, Anam-dong, Seongbuk-gu, Seoul 136-701, Korea
Abstract
Fluid catalytic cracking (FCC) is one of the most important refinery processes for economical efficiency that produces commercial fuels with acceptable concentrations of sulfur. Several activated carbon (AC) based adsorbents were studied to develop a more efficient adsorbent for removal of mercaptanes and sulfides during the FCC C4 refinery process. The adsorbents were prepared by impregnating AC with CuCl and PdCl2. To evaluate the degree of metal halide impregnation into the AC support, each adsorbent was characterized by N2 adsorption, elemental analysis (EA) and XRF. Three types of ACs were used to investigate the effect of the structural properties such as surface area, total pore volume and pore size distribution. From this analysis, an AC micro pore size of 0.7 nm was found to be the most effective support material for FCC C4 removal of sulfur compounds. The experimental adsorption isotherms were compared with Langmuir and Freundlich models and were found to fit the Freundlich model much better than the Langmuir model. The sulfur removal performance of the prepared adsorbents was tested using the breakthrough experiments. The sulfur adsorption capacities of adsorbents decreased in the following order: AC impregnated PdCl2, AC impregnated CuCl and non-impregnated AC (NIAC). The saturated adsorbents were regenerated by toluene treatment and reactivated at 130 oC under a vacuum. Key words: Sulfur Removal, Desulfurization, Adsorption, Activated Carbon Adsorbent, CuCl Adsorbent, PdCl2 Adsorbent, Impregnation, FCC
INTRODUCTION
As the estimated amount of oil deposits continually dwindles and the price of oil continues to increase, it has become necessary to refine crude oil that contains a high sulfur content. The total content of sulfur in oil products is currently much higher than the acceptable limit in some places [1,2]. The sulfur content should be lower than 1.0 ppmw to avoid poisoning the catalysts in the emission control systems of vehicles. The SOX that is produced from the combustion of oil with a high sulfur content is harmful to human health and it may cause acidic rain. Therefore, there is currently a pressing need for methods that can remove high levels of sulfur from oil. In fact, the U.S. environmental protection agency (EPA) has already issued a mandate that the total sulfur content must be dropped down to 5 and 10 ppmw in diesel and gasoline, respectively, before 2010. Similar stringent new regulations are being implemented in Europe and Japan. Sulfur-free fuel has been a goal in all countries across the world. Various refinery processes are being developed all over the world to produce refined economic and sulfur free commercial fuels.
Among these processes, the FCC process is one of the most economical efficient refinery processes for the conversion of relatively heavy hydrocarbons to lighter hydrocarbons. Some FCC based refineries can lower the level of sulfur during the refinery process by using various catalysts and/or adsorbents. In fact, various desulfurization processes are being developed to remove sulfur compounds from commercial fuels. Of these methods, the hydrodesulfurization (HDS) processes have been most extensively employed to reduce sulfur levels from commercial fuels. However, it is difficult to reduce sulfur levels using the current HDS process because of the very low reactivity of the HDS catalysts towards sulfur compounds [3,4]. An increase in the reactor size and hydrogen consumption is required to achieve high levels of desulfurization [5]. Extensive research has been carried out to find adsorbent materials that are highly selective toward just sulfur compounds. One way to avoid increased costs is to use different approaches like an adsorption process that operates at ambient condition.
Desulfurization of commercial fuels by selective adsorption has been reported as an alternative technology for the current HDS method. Yang and coworkers reported using zeolites for selective adsorption under ambient conditions for the desulfurization of commercial fuels [6-10]. Metal ion-exchange Y zeolites have also been shown to effectively remove sulfur compounds under ambient conditions. However, the sulfur adsorption capacity depends on the composition of the fuel. Adsorptive removal of sulfur compounds from liquid commercial fuels has been widely investigated using various different adsorbents such as porous carbon materials [11,12], metal impregnated oxides [13], zeolite 5A [14], 13X [15,16] and Y zeolites of various metal cation forms [17,18]. Among these absorbents, Ag-Y and Cu-Y zeolites have been shown to have a particularly high adsorption capacity and selectivity for thiophene and its derivatives via p-complexation.
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THESIS
Catalytic Oxidative Desulfurization of a Model Diesel
Liu, Dongxing (2010)
A Thesis Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Master of Science in Chemical Engineering in The Gordon A. and Mary Cain Department of Chemical Engineering
Abstract
An analysis of heterogeneous oxidation catalysts was performed to determine the activities and optimal operating conditions for the multiphase oxidative desulfurization (ODS) reactions, using a model diesel. Catalysts studied included well-characterized Pd on Al2O3 and activated carbon supports, and carbon-supported Mo2C and W2C, which were prepared by temperature programmed reaction. Several other typical oxidation catalysts were also examined. The model diesel consisted of ~1 wt% sulfur compounds (thiophene and dibenzothiophene) with appropriate amounts of aliphatic, alkylaromatic and N-heterocyclic compounds to simulate a raw number 2 diesel. With oxygen as the oxidant in ODS reactions of this model diesel (70-90ºC, 0.8-1.8 MPa, feed vol/wt cat. = 100 mL/g), Pd/C and Mo2C/C showed the best selectivity for oxidizing the N- and S-heterocycles vs. the alkylaromatics. Increasing the pressure increased the reaction rates of the N- and S-heterocycles. Except for thiophene, there was only a small dependence of observed rates on temperature, which suggests the reactions were partially diffusion (of O2) controlled. The optimal ODS catalysts (carbides and 5%Pd/MPT-5) also showed high activity for the conversion of N-heterocycles. Current work includes further investigations of the better catalysts, full characterization of the products by GC-MS, and kinetics measurements using catalyst monoliths in a pistonoscillating reactor, which can eliminate the diffusion limitations and provide a uniform hydrodynamic environment.
Free Full Text Source: http://etd.lsu.edu/docs/available/etd-06032010-071804/
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THESIS
Botchwey, Christian
A Thesis Submitted to the College of Graduate Studies and Research in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in the Department of Chemical Engineering University of Saskatchewan
Abstract
This thesis summarizes the methods and major findings of Ni-W(P)/ã-Al2O3 nitride cata-lyst synthesis, characterization, hydrotreating activity, kinetic analysis and correlation of the catalysts’ activities to their synthesis parameters and properties.
The range of parameters for catalyst synthesis were W (15-40 wt%), Ni (0-8 wt%), P (0-5 wt%) and nitriding temperature (TN) (500-900 °C). Characterization techniques used included: N2 sorption studies, chemisorption, elemental analysis, temperature programmed studies, x-ray diffraction, scanning electron microscopy, energy dispersive x-ray, infrared spectroscopy, trans-mission electron microscopy and x-ray absorption near edge structure. Hydrodesulfurization (HDS), hydrodenitrogenation (HDN) and hydrodearomatization (HDA) were performed at: tem-perature (340-380 °C), pressure (6.2-9.0 MPa), liquid hourly space velocity (1-3 h-1) and hydro-gen to oil ratio (600 ml/ml, STP).
The predominant species on the catalyst surface were Ni3N, W2N and bimetallic Ni2W3N. The bimetallic Ni-W nitride species was more active than the individual activities of the Ni3N and W2N. P increased weak acid sites while nitriding temperature decreased amount of strong acid sites. Low nitriding temperature enhanced dispersion of metal particles. P interacted with Al2O3 which increased the dispersion of metal nitrides on the catalyst surface. HDN activity in-creased with Ni and P loading but decreased with increase in nitriding temperature (optimum conversion; 60 wt%). HDS and HDA activities went through a maximum with increase in the synthesis parameters (optimum conversions; 88. wt% for HDS and 47 wt% for HDA). Increase in W loading led to increase in catalyst activity. The catalysts were stable to deactivation and had the nitride structure conserved during hydrotreating in the presence of hydrogen sulfide.
The results showed good correlation between hydrotreating activities (HDS and HDN) and the catalyst nitrogen content, number of exposed active sites, catalyst particle size and BET surface area.
HDS and HDN kinetic analyses, using Langmuir-Hinshelwood models, gave activation energies of 66 and 32 kJ/mol, respectively. There were no diffusion limitations in the reaction process. Two active sites were involved in HDS reaction while one site was used for HDN. HDS and HDN activities of the Ni-W(P)/ã-Al2O3 nitride catalysts were comparable to the corre-sponding sulfides.
Free Full Text Source: http://library2.usask.ca/theses/available/etd-07192010-092232/
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THESIS
University of Saskatchewan
Sigurdson, Stefan Kasey
A thesis submitted to the College of Graduate Studies & Research in partial fulfillment of the requirements for the Master of Science Degree in the Department of Chemical Engineering,
Abstract
Multi-walled carbon nanotubes (MWCNTs) are a potential alternative to commonly used catalyst support structures in hydrotreating processes. Synthesis of MWCNTs with specific pore diameters can be achieved by chemical vapor deposition (CVD) of a carbon source onto an anodic aluminum oxide (AAO) template. AAO films consist of pore channels in a uniform hexagonal arrangement that run parallel to the surface of the film. These films are created by the passivation of an aluminum anode within an electrolysis cell consisting of certain weak acid electrolytes. Changing the concentration of the electrolyte (oxalic acid) and the electrical potential of the electrolysis cell altered the pore channel diameter of these AAO films. Controlling the pore diameter of these templates enabled the pore diameter of MWCNTs synthesized by CVD to be controlled as well. The produced MWCNTs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Raman spectroscopy, and N2 adsorption analysis. Anodizing conditions of 0.40 M oxalic acid concentration and 40.0 V maximum anodizing potential were found to produce AAO films that resulted in MWCNTs with optimum surface characteristics for a catalyst support application. CVD parameter values of 650°C reaction temperature and 8.00 mL/(min·g) C2H2-to-AAO ratio were found to produce the highest yield of MWCNT product.
The MWCNTs were synthesized for the purpose of supporting hydroprocessing catalysts, with several grades of NiMo/MWCNT sulfide catalysts being prepared to determine the optimum pore size. These catalysts were characterized by techniques of TEM, CO chemisorption, N2 adsorption, and H2 temperature programmed reduction (TPR). A MWCNT grade with 67 nm inner diameters (found from TEM analysis) was found to offer the best hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) activities for the treatment of coker light gas oil (CLGO). After determining the most suitable pore diameter, the optimum catalyst metal loadings were found to be 2.5 wt.% for Ni and 19.5 wt.% for Mo. The optimum catalyst was found to offer HDS conversions of 90.5%, 84.4%, and 73.5% with HDN conversions of 75.9%, 65.8%, and 55.3% for temperatures of 370°C, 350°C, and 330°C, respectively. An equal mass loading of commercial NiMo/ã-Al2O3 catalyst offered HDS conversions of 91.2%, 77.9%, and 58.5% with HDN conversions of 71.4%, 53.2%, and 31.3% for temperatures of 370°C, 350°C, and 330°C, respectively.
A kinetic study was performed on the optimum NiMo/MWCNT catalyst to help predict its HDS and HDN activities while varying the parameters of temperature, liquid hourly space velocity (LHSV), pressure, and gas-to-oil flow rate ratio. Rate expressions were then developed to predict the behavior of both the HDS and HDN reactions. Power law models were best fit with reaction orders of 2.6 and 1.2, and activation energies of 161 kJ/mol and 82.3 kJ/mol, for the HDS and HDN reactions, respectively. Generalized Langmuir-Hinshelwood models were found to have reaction orders of 3.0 and 1.5, and activation energies of 155 kJ/mol and 42.3 kJ/mol, for the HDS and HDN reactions, respectively.
Free Full Text Source: http://library2.usask.ca/theses/available/etd-01072010-162623/
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