Sulfur Regulation Research Articles

Economic repercussions of sulfur regulations in Poland

Using applied general equilibrium techniques, it is possible to compute alternative equilibria for different policy regimes and to assess impacts of the changes. We have used these techniques to verify economy-wide effects of SO 2 emission reduction in Poland according to international sulfur agreement. Simulation results suggest that future emission reduction may have a positive effect on Polish economic indicators. We should not be afraid of a slump in emitting sectors. Some sectors may increase their SO 2 emission and abate it afterwards, rather than decrease their emission at once. The poor households may even gain because their welfare effect will be positive.

Economic modelling of sulphur regulations in Poland

This study presents an assessment of the possible consequences of reducing the emission of sulfur dioxide in Poland according to international sulfur agreement. A computable general equilibrium model was used for this purpose. The model, calibrated for 1995, provides results for year 2010 which suggest that future emission reductions may have positive effects on Polish economic indicators. We should not fear an economic slump in the emitting sectors. Some sectors may increase their sulfur dioxide emissions initially and abate them later, rather than decrease their emissions at once. Poor households may gain, because the welfare effect on them will be positive.

The effect of sulfur regulations on the U.S. electric power industry: a generalized cost approach

This paper estimates the effects of sulfur dioxide emission regulations on the US electric power industry during the 1975–1990 period by utilizing a generalized cost function along with shadow input prices. In the presence of various regulations, including those intended to control sulfur dioxide emissions, firms will likely fail to minimize production costs. The null hypothesis of cost minimization is rejected, implying that the use of a neoclassical cost function is inappropriate for this study. A comparison of the results obtained by estimating a generalized cost function and those obtained with a neoclassical cost function reveals that the use of a neoclassical restriction brings an underestimation of the average percentage increase in cost by 1.1 percentage points.

An additional role for the F-box motif: gene regulation within the Neurospora crassa sulfur control network.

The F-box represents a protein motif originally identified as a conserved amino-terminal domain within the Neurospora crassa negative regulator sulfur controller-2. Recently, F-boxes have been found within a number of cell cycle regulatory proteins, where they mediate ubiquitin-driven proteolytic events required for major cell cycle transitions. F-box function, however, is not restricted solely to cell cycle pathways. Here we present evidence expanding F-box function to encompass gene regulatory processes independent of the cell cycle through in vivo analysis of an F-box acting within the N. crassa sulfur regulatory network. The Neurospora sulfur circuit features a set of regulatory genes acting to modulate gene expression based on environmental sulfur conditions. These sulfur regulatory genes include cys-3+, which encodes a basic region-leucine zipper transcriptional activator, as well as the negative regulatory gene scon-2+. Through site-directed mutagenesis of the SCON2 F-box, we have generated a sulfur auxotrophic phenotype previously unobserved in any scon-2 mutant. Using Northern analysis, we have traced this auxotrophy to a complete shutdown of cys-3+ gene expression. We have further analyzed F-box function by constructing a series of chimeric SCON2 proteins containing swapped F-box domains from the yeast transcriptional inhibitor Met30p and the Candida albicans cell cycle regulator Cdc4p. The ability of these chimeric proteins to restore partial wild-type sulfur regulation in vivo emphasizes the universal nature of this motif and confirms the functional importance of the F-box within noncell cycle regulatory pathways.

Molecular genetics of sulfur assimilation in filamentous fungi and yeast.

The filamentous fungi Aspergillus nidulans and Neurospora crassa and the yeast Saccharomyces cerevisiae each possess a global regulatory circuit that controls the expression of permeases and enzymes that function both in the acquisition of sulfur from the environment and in its assimilation. Control of the structural genes that specify an array of enzymes that catalyze reactions of sulfur metabolism occurs at the transcriptional level and involves both positive-acting and negative-acting regulatory factors. Positive trans-acting regulatory proteins that contain a basic region, leucine zipper-DNA binding domain, are found in Neurospora and yeast. Each of these fungi contain a sulfur regulatory protein of the beta-transducin family that acts in a negative fashion to control gene expression. Sulfur regulation in yeast also involves the general DNA binding protein, centromere binding factor I. Sulfate uptake is a highly regulated step and appears to occur in fungi, plants, and mammals via a family of related transporter proteins. Recent developments have provided new insight into the nature and control of the enzymes ATP sulfurylase and APS kinase, which catalyze the early steps of sulfate assimilation, and of the Aspergillus enzyme, cysteine synthase, which produces cysteine from O-acetylserine.

Global regulation of sulfur assimilation in Neurospora

A complex regulatory circuit controls expression of many permeases and enzymes involved in sulfur assimilation in the filamentous fungus Neurospora crassa. CYS3, the global positive-acting sulfur regulatory protein, turns on the expression of structural genes that encode sulfur enzymes when N. crassa cells are limited for sulfur. Expression of the cys-3 gene itself is highly regulated by negative-acting sulfur-controller scon genes and by autogenous regulation. The CYS3 protein is localized within the nucleus and contains a bZip DNA-binding motif and regions rich in alanine and in proline that appear to function in trans activation. Amino acid substitutions for basic or neutral amino acids in the bZip domain of CYS3 lead to significant changes in its DNA-binding activity. Key words: sulfur regulation, CYS3, autogenous control, leucine zipper, trans activation.

Organic geochemistry characterization of the density fractions of a Permian torbanite

The utilization of high-sulfur coal is becoming more urgent due to the excessive utilization of low-sulfur, high-quality coal resources, and sulfur removal from high-sulfur coal is the most important issue. This paper reviews the speciation, forms and distribution of sulfur in coal, the sulfur removal from raw coal, the thermal transformation of sulfur during coal pyrolysis, and the sulfur regulation during coal-blending coking of high organic-sulfur coals. It was suggested that the proper characterization of sulfur in coal cannot be obtained only by either chemical method or instrumental characterization, which raises the need of a combination of current or newly adopted characterization methods. Different from the removal of inorganic sulfur from coal, the organic sulfur can only be partly removed by chemical technologies; and the coal structure and property, particularly high-sulfur coking coals which have caking ability, may be altered and affected by the pretreatment processes. Based on the interactions among the sulfur radicals, sulfur-containing and hydrogen-containing fragments during coal pyrolysis and the reactions with minerals or nascent char, regulating the sulfur transformation behavior in the process of thermal conversion is the most effective way to utilize high organic-sulfur coals in the coke-making industry. An in-situ regulation approach of sulfur transformation during coal-blending coking has been suggested. That is, the high volatile coals with an appropriate releasing temperature range of CH4 overlapping well with that of H2S from high organic-sulfur coals is blended with high organic-sulfur coals, and the C–S/C–C bonds in some sulfur forms are catalytically broken and immediately hydrogenated by the hydrogen-containing radicals generated from high volatile coals. Wherein, the effect of mass transfer on sulfur regulation during the coking process should be considered for the larger-scale coking tests through optimizing the ratios of different coals in the coal blend.

Biochemical mechanisms for the desulfurization of coal-relevant organic sulfur compounds

Two microbial strains ( Brevibacterium sp. DO, Pseudomonas aeruginosa OS1) were isolated for their ability to desulfurize dibenzothiophene (DBT) and benzyl methyl sulfide (BMS). Enrichment was achieved by a sulfur-selective screening system using the model compounds as the sole source of sulfur for bacterial growth. Brevibacterium sp. DO utilizes DBT as a sole source of sulfur, carbon and energy for growth, whereas Pseudomonas aeruginosa OS1 metabolizes BMS to only a small extent under sulfur-selective conditions. Investigations of the regulation of enzymes involved in the desulfurization of coal-relevant sulfur compounds indicate that in nature at least two mechanisms exist: ‘carbon regulation’ and ‘sulfur regulation’. The biochemical mechanisms leading to the desulfurization of BMS and DBT are similar. The sulfur atom of both compounds is initially oxidized to the corresponding sulfone, and cleavage of the CS bond proceeds via the formation of a chemically unstable hemimercaptal (S-oxidized form) by oxidation of the carbon atom adjacent to the sulfur atom. These results indicate that oxidation of sulfur to its highest oxidation state may be the precondition for the oxidative cleavage of the covalent CS bonds. By isotope-labelling experiments using 18O 2, the initial enzymes were identified as sulfoxygenases that use molecular oxygen. Cleavage of the CS bond of DBT and BMS leads to the formation of organic sulfinic acids as intermediates. With DBT the sulfinic acid is desulfurized probably by hydrolysis; this results in the formation of sulfite and benzoate. The desulfurization of BMS proceeds by sulfonic acid-oxidation. The applicability of these biochemical mechanisms to the microbial desulfurization of coal is discussed.

Regulation of Sulfur and Nitrogen Metabolism in Filamentous Fungi

Regulation of Sulfur and Nitrogen Metabolism in Filamentous Fungi

Molecular Cloning and Analysis of the scon-2 Negative Regulatory Gene of Neurospora crassa

The sulfur regulatory system of Neurospora crassa is composed of a group of highly regulated structural genes (e.g., the gene encoding arylsulfatase) that are under coordinate control of scon+ (sulfur controller) negative and cys-3+ positive regulatory genes. In scon-1 (previously designated sconC) and scon-2 mutants, there is constitutive expression of sulfur structural genes regardless of the sulfur level available to the cells. The scon-2+ gene was cloned by sib selection screening of a cosmid-based gene library. The screening was based on the use of chromate, a toxic sulfate analog, which is transported into scon-2 cells grown on high sulfur but is not transported into cells that have regained normal sulfur regulation. Restriction fragment length polymorphism analysis was used to confirm that the cloned segment mapped to the proper chromosomal location. In wild-type cells, Northern (RNA) blot analysis showed that a 2.6-kilobase scon-2+ transcript was present at a substantial level only under sulfur-derepressing conditions. Kinetic analysis showed that scon-2+ mRNA content increased as the cells became sulfur starved. Further, scon-2+ RNA was detectable in a nuclear transcription assay only under derepressing conditions. In scon-1, the levels of scon-2+ mRNA were found to be constitutive. In the cys-3 regulatory mutant, there was a reduced level of scon-2+ transcript. cys-3+ and ars-1+ mRNAs were present under both derepressing and repressing conditions in the scon-2 mutant. Repeat-induced point mutation-generated scon-2 mutants were identical in phenotype to the known mutant.

Molecular cloning and analysis of the scon-2 negative regulatory gene of Neurospora crassa.

The sulfur regulatory system of Neurospora crassa is composed of a group of highly regulated structural genes (e.g., the gene encoding arylsulfatase) that are under coordinate control of scon+ (sulfur controller) negative and cys-3+ positive regulatory genes. In scon-1 (previously designated sconC) and scon-2 mutants, there is constitutive expression of sulfur structural genes regardless of the sulfur level available to the cells. The scon-2+ gene was cloned by sib selection screening of a cosmid-based gene library. The screening was based on the use of chromate, a toxic sulfate analog, which is transported into scon-2 cells grown on high sulfur but is not transported into cells that have regained normal sulfur regulation. Restriction fragment length polymorphism analysis was used to confirm that the cloned segment mapped to the proper chromosomal location. In wild-type cells, Northern (RNA) blot analysis showed that a 2.6-kilobase scon-2+ transcript was present at a substantial level only under sulfur-derepressing conditions. Kinetic analysis showed that scon-2+ mRNA content increased as the cells became sulfur starved. Further, scon-2+ RNA was detectable in a nuclear transcription assay only under derepressing conditions. In scon-1, the levels of scon-2+ mRNA were found to be constitutive. In the cys-3 regulatory mutant, there was a reduced level of scon-2+ transcript. cys-3+ and ars-1+ mRNAs were present under both derepressing and repressing conditions in the scon-2 mutant. Repeat-induced point mutation-generated scon-2 mutants were identical in phenotype to the known mutant.

Sulfur regulation of heparinase and sulfatases in Flavobacterium heparinum.

Sulfur regulation of heparinase synthesis and sulfatase synthesis was studied in Flavobacterium heparinum. Heparinase synthesis was strongly repressed by sulfate and L-cysteine, while the activity of this enzyme showed little or no inhibition by these compounds. Heparinase was synthesized in the absence of heparin when L-methionine was used as the sole sulfur source. The sulfatases produced by F. heparinum, which include the sulfatases involved in heparin catabolism, were also studied. At least some of the sulfatase activity was regulated by sulfur compounds in a manner similar to heparinase regulation. L-Cysteic acid and taurine were not suitable sulfur sources to support the growth of F. heparinum.

Isolation and characterization of lac fusions to two nitrogen-regulated promoters.

Mud1 (Ap, lac, cts)-mediated fusions to argTr and dhuA, two transport operon promoters in Salmonella typhimurium, were isolated and characterized in order to investigate the regulation of these promoters. Using these fusions we showed that these promoters are under nitrogen regulation and that this effect, as well as the response to a promoter-up mutation in dhuA, is at the transcriptional level. We utilized the fusions to determine that the histidine transport operon does not contain any internal promoters. The fusions were also used to screen the promoters for additional modes of regulation: argTr was found to respond to carbon regulation in addition to nitrogen regulation, while dhuA does not. The argTr promoter contains a sequence with good homology to the consensus sequence determined for the cAMP receptor protein binding site. Neither promoter responds to sulfur or phosphate regulation.

Time Series Analysis of Coal Data from Preparation Plants

The body of information presented in this paper is directed to those individuals concerned with existing or proposed sulfur emission regulations. The ability of coal-fired boiler operators to comply with emission regulations depends largely on the variability in emission rate. Because of the variability inherent in coal, the mean emission rate (in Ib SO2/million Btu) must be lower than the emission standard to prevent violations. Heretofore, this problem has been analyzed by statistical techniques assuming independent (uncorrelated) data. The results of this paper indicate that this method is inappropriate. Failure to account for correlation structure in coal data results in gross underestimation of emission violations of actual coal. It is concluded that correlation in coal data should not be overlooked, and that the ability of each coal to meet emission regulations must be individually determined by procedures outlined in this paper.