Synthesis of lsopropyl-1-thio-Β-D-glucopyranoside (IPTGlc), an inducer ofaspergillus niger b1 Β-glucosidase production

Production of Β-glucosidase inAspergillus niger Bl is subjected to catabolic repression by glucose.Aspergillus niger Bl grown on bran as a carbon source secreted Β-glucosidase. The maximum level of the enzyme was reached after 7 d of fermentation. Addition of 1% glucose to the medium suppressed Β-glucosidase production to undetectable levels. In this study, the organic synthesis of a potential inducer of Β-glucosidase production by A.niger Bl’s reported. Isopropyl-1-thio-Β-D-glucopyranoside (IPTGlc) was synthesized using a two-step organic synthesis protocol. The H-NMR data agreed with those reported previously for the galactoside analog. When IPTGlc was added 24 h after inoculation at a final concentration of 0.4 mM, similar levels of Β-glucosidase were reached 3 to 4 d earlier as compared to fermentation without IPTGlc induction. In practice, this may translate to a more efficient method of producing Β-glucosidase from this fungus.     

Xylanolytic enzyme production by anAspergillus niger isolate

Production of xylanolytic enzymes by anAspergillus niger CCMI 850 isolate was investigated in batch cultures. The effect of the composition of a fermentation medium that did not include chemical inducers, on β-xylanase, β-xylosidase, α-l-arabinofuranosidase, and total cellulase activity was studied. With 4% xylan as the carbon source, about 65 U/mL of β-xylanase was obtained, whereas the total cellulase activity was undetectable, under the specified conditions. This β-xylanase activity represents the highest reported for a wild-type strain ofA. niger. The effect of pH and temperature on the activity of β-xylanase was studied. Partial characterization of the β-xylanase showed that with insoluble birchwood as substrate theK _m andV _max were 0.3 mM and 19 μmol/min, respectively. Aspects of using the crude β-xylanase preparation for applications in the pulp and paper industry were discussed.     

Enhanced production of xylanase from locally isolated fungal strain using agro-industrial residues under solid-state fermentation

This study is related to the isolation of fungal strain for xylanase production using agro-industrial residues. Forty fungal strains with xylanolytic potential were isolated by using xylan agar plates and quantitatively screened in solid-state fermentation. Of all the tested isolates, the strain showing highest ability to produce xylanase was assigned the code Aspergillus niger LCBT-14. For the enhanced production of the enzyme, five different fermentation media were evaluated. Out of all media, M4 containing wheat bran gave maximum enzyme production. Effect of different variables including incubation time, temperature, pH, carbon and nitrogen sources has been investigated. The optimum enzyme production was obtained after 72 h at 30°C and pH 4. Glucose as a carbon source while ammonium sulphate and yeast extract as nitrogen sources gave maximum xylanase production (946 U/mL/min). This study was successful in producing xylanase by A. niger LCBT-14 economically by utilising cheap indigenous substrate.     

Pretreatment of sugar cane bagasse hemicellulose hydrolyzate for ethanol production by yeast

The cellulase system ofBacillus circulans F-2 effectively hydrolyzed carboxymethyl cellulose (CMC), xylan, avicel, cellobiose, filter paper, cotton, andp-nitrophenyl-Β-D-cellobioside, and the crude enzyme produced mainly glucose from digestion of avicel. Two major and one minor peaks of enzyme activities were eluted on DEAE ion-exchange chromatography, and designated cellulase complex I(C-I) and complex II(C-II) for the two major peaks, and cellulase-III for a minor peak. C-I and C-II were further purified on gel filtration column of a TSK-Gel SW G3000 ×L. The molecular masses of C-I and C-II were estimated to be about 669 and 443 kDa, respectively. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of the C-I and C-II complexes showed that the C-I complex was present as a multiple protein complex, consisting of at least five CMCases and two xylanases, and that the C-II complex was consisted of at least three CMCase and four xylan ases. C-I showed high activities of cellohydrolase, CMCase, xylanase, and Β-glucosidase, whereas C-II showed high activities of CMCase, xylanase, avicelase, and Β-glucosidase. The outstanding property of the C-II was its high hydrolytic activity toward filter paper, a highly resistant substrate against enzymatic degradation. However, cellulaseIII showed only strong avicelase activity. These results indicated that the cellulase system of the strain exists as multiple complex forms.     

Xylanase production by Aspergillus awamori in solid-state fermentation and influence of different nitrogen sources

The use of purified xylan as a substrate for bioconversion into xylanases increases the cost of enzyme production. Consequently, there have been attempts to develop a bioprocess to produce such enzymes using different lignocellulosic residues. Filamentous fungi have been widely used to produce hydrolytic enzymes for industrial applications, including xylanases, whose levels in fungi are generally much higher than those in yeast and bacteria. Considering the industrial importance of xylanases, the present study evaluated the use of milled sugarcane bagasse, without any pretreatment, as a carbon source. Also, the effect of different nitrogen sources and the C∶N ratio on xylanase production by Aspergillus awamori were investigated, in experiments carried out in solid-state fermentation. High extracellular xylanolytic activity was observed on cultivation of A. awamori on milled sugarcane bagasse and organic nitrogen sources (45 IU/mL for endoxylanase and 3.5 IU/mL for β-xylosidase). Endoxylanase and β-xylosidase activities were higher when sodium nitrate was used as the nitrogen source, when compared with peptone, urea, and ammonium sulfate at the optimized C∶N ratio of 10∶1. The use of yeast extract as a supplement to the these nitrogen sources resulted in considerable improvementin the production of xylanases, showing the importance of this organic nitrogen source on A. awamori metabolism.     

Characteristics and production of thermostable α-amylase

Thermostable α-amylases have application in a variety of industrial processes and enzymes from a substantial number of thermophilic bacteria and fungi have been screened and characterized to varying degrees. The characteristics of these enzymes are summarized in this review. The genetics of α-amylase production inBacillus subtilis is reviewed and classical and recombinant DNA approaches to increasing α-amylase production are discussed.     

Effect of media composition and growth conditions on production of β-glucosidase by Aspergillus niger C-6

The hydrolytic activity of fungal originated β-glucosidase is exploited in several biotechnological processes to increase the rate and extent of saccharification of several cellulosic materials by hydrolyzing the cellobiose which inhibits cellulases. In a previous presentation, we reported the screening and liquid fermentation with Aspergillus niger, strain C-6 for β-glucosidase production at shake flask cultures in a basal culture medium with mineral salts, corn syrup liquor, and different waste lignocellulosic materials as the sole carbon source obtaining the maximum enzymatic activity after 5–6 d of 8.5 IU/mL using native sugar cane bagasse. In this work we describe the evaluation of fermentation conditions: growth temperature, medium composition, and pH, also the agitation and aeration effects for β-glucosidase production under submerged culture using a culture media with corn syrup liquor (CSL) and native sugar cane bagasse pith as the sole carbon source in a laboratory fermenter. The maximum enzyme titer of 7.2 IU/mL was obtained within 3 d of fermentation. This indicates that β-glucosidase productivity by Aspergillus niger C-6 is function of culture conditions, principally temperature, pH, culture medium conditions, and the oxygen supply given in the bioreactor. Results obtained suggest that this strain is a potential microorganism that can reach a major level of enzyme production and also for enzyme characterization.     

Biotransformation of (−)β-pinene by Aspergillus niger ATCC 9642

The main objective of this work was to investigate the biotransformations of (−)α-pinene, (−)β-pinene, and (+) limonene by Aspergillus niger ATCC 9642. The culture conditions involved—concentration of cosolvent (EtOH), substrate applied, and sequential addition of substrates—were investigated. Adaptation of the precultures with small amounts of substrate was also studied. The experiments were performed in conical flasks with liquid cultures. This strain of A. niger was able to convert only (−)β-pinene into α-terpineol. An optimum conversion of (−)β-pinene into α-terpineol of about 4% was obtained when the substrate was applied as a diluted solution in EtOH and sequential addition of substrate was used.     

Uncoupled metabolism stimulated by chemical uncoupler and oxic-settling-anaerobic combined process to reduce excess sludge production

The effects of three uncoupled metabolic systems (conventional activated sludge process with the addition of 3,3′,4′,5-tetrachlorosalicylanilide [TCS], oxic-settling-anaerobic [OSA] process modified by insertion of a sludge-holding tank in the sludge return line, and TCS and OSA combined process) on reducing excess sludge production were studied. Compared with the control conventional activated sludge process, the most effective system was the combined process, which could reduce excess sludge production by 46.90%. The 180-d operation results confirmed that TCS is an effective chemical uncoupler in reducing the sludge yield but that it had an adverse effect on substrate removal capability, effluent nitrogen concentration, and sludge settleability. The OSA process decreased excess sludge production by only 26% but had less adverse effect on effluent quality and could improve sludge settleability. The effluent total phosphorous concentration of the three systems was slightly lower than of the control unit. Microbial populations were monitored by both microscopic and molecular biologic analysis method (polymerase chain reaction [PCR]-denaturing gradient gel electrophoresis [DGGE]). The presence of TCS caused metazoans to disappear and decreased the number and activity of protozoa. PCR amplification of 16S rRNA and sequent DGGE analysis found a shift in the diversity of the predominant species. The results imply that OSA combined with the chemical uncoupler process may effectively reduce excess sludge yield and not affect process performance significantly.     

A theoretical study on the ionization of OCS with an analysis of vibrational structures of the photoelectron spectrum

 Ab initio calculations have been performed to study the molecular structures and vibrational levels of the four low-lying ionic states (1, 2²Π, and 1, 2²Σ⁺) of carbonyl sulfide. The global regions of the potential-energy surfaces have been obtained by multireference single and double excitation configuration interaction calculations. Vibrational calculations using explicit vibrational Hamiltonians have been used for vibrational analysis. The equilibrium molecular structures and a vibrational analysis of the four ionic states are presented. The theoretical ionization intensity curves including the vibrational structures of the ionic states are also presented and are compared with the photoelectron spectrum. Received: 20 January 2001 / Accepted: 22 August 2001 / Published online: 30 October 2001     

Supramolecular Ribbons. Crystal Structure and Spectroscopic Properties of 2,2′-Bipyrroyl

Summary.  A crystal structure determination of 2,2′-bipyrroyl (1; 2,2′-dipyrryl-diketone, bis (2-pyrrolyl)ethanedione) and its spectroscopic properties in solution are reported. In the crystal, 1 self-assembles via hydrogen bonding into supramolecular ribbons that extend indefinitely through the crystal lattice. The observed molecular conformation is one where each pyrrole ring and adjacent carbonyl group are co-planar (torsion angle ∼ 0.9°), with the N-H pointing in the same direction as the C=O. The two carbonyls have a transoid but not co-planar geometry with a torsion angle of ∼128°. Adjacent molecules in the crystal are linked by pairs of intermolecular hydrogen bonds, pyrrole NH to carbonyl oxygen, to form a matrix of polymeric chains that lie like neatly stacked, parallel streams of ribbons. Molecular mechanics calculations on the monomer indicate an intra-molecularly hydrogen bonded planar conformation (sp, ap, sp) at the global energy minimum. In CHCl₃, 1 is monomeric according to vapor pressure osmometry (MW _obs=179±10 vsċMW _calc=188). In THF, the measured molecular weight is 340±15, which corresponds best to one molecule of 1 solvated by two THF molecules (MW=322 for C₁₀H₈N₂O₄ċ2 C₄H₈O) rather than to a dimer. Received October 21, 1999. Accepted November 2, 1999     

Proficiency testing on the analytical control of precious metal production

Our experience of executing proficiency testing programs on the analysis of precious metals and precious metal bearing materials is summarized. Six proficiency testing programs of the ”distributed sample testing” type were carried out using samples essentially distinct from each other: (I) certified samples of fine gold and fine silver, and (II) recoverable raw (scrap and catalyst waste) containing precious metals of unknown contents. The test results were assessed using the London Bullion Market Association (LBMA) rules and by Z-criteria using the ISO/IEC Guide 43 scale. Satisfactory results were presented by all participants for the analysis of certified samples of fine gold and fine silver. The results of catalyst waste analysis agreed rather well, whereas the scrap analysis revealed an essential discrepancy in the data for some samples. The reasons for such discrepancies are discussed. Received: 9 June 2000 Accepted: 21 November 2000     

Metrological role of neutron activation analysis. IB. Inherent characteristics of relative INAA as a primary ratio method of measurement

This is the second part of a paper which deals with the advantages and disadvantages of relative instrumental neutron activation analysis concerning traceability and uncertainty, and the current scope and possible future extensions of neutron activation analysis as a primary ratio method. The first part of this paper has been published in this Journal [1]. Received: 19 March 2001 Accepted: 2 October 2001     

Use of calibration gases in the U.S. acid rain program

The United States Acid Rain Program continuous emission monitors (CEMs) have been successful in producing quality-assured data 95% of the time, and in meeting a relative accuracy standard of less than or equal to 10.0% at over 99% of the CEMs in the program. One key reason for this high accuracy is the required use of high quality calibration gases in certification and quality assurance/quality control (QA/QC) tests. An annual QA audit helps ensure high quality calibration gases. A third party purchases gases from gas vendors. An Environmental Protection Agency (EPA) laboratory analyzes the gases and compares the results with the tag value on the cylinder. The results are posted on an EPA website. This allows purchasers of calibration gases to buy gases from vendors producing the most accurate gases. Over time, we believe it also results in better accuracy from all gas vendors. Because of a change in SO₂ quantification methodology, SO₂ emissions were underreported by approximately 2% between 1989 and 1996. EPA, the National Institute for Standards and Technology and calibration gas vendors collaborated to produce a correction policy and a standard correction form to be used by affected electric utility plants. Calibration gas cylinder tag values were required to be corrected by 1 January, 1997. In the future, it is possible that cleaner, more varied sources will be regulated for greenhouse effect, ozone and toxic emissions control. This will probably require more accurate CEMs, lower calibration gas concentrations, and a broader menu of gas mixtures. Received: 23 December 1999 Accepted: 12 December 2000     

Ab initio molecular orbital study of Fe(CO) n (n = 1–3)

Geometry optimization was performed for the ground states of FeCO, Fe(CO)₂, and Fe(CO)₃ at various levels of ab initio calculations, and the bond lengths and dissociation energies obtained were in reasonable agreement with experimental results. The nature of bonding was studied for these molecules using a complete-active-space self-consistent-field method. From the Mulliken population analysis, it was found that the traditional donation and back donation mechanism is valid for these molecules, including Fe(CO)₃, which has a pyramidal structure. Received: 27 September 1999 / Accepted: 13 January 2000 / Published online: 19 April 2000     

Solid-state interactions and drug release of teicoplanin in binary combinations with peracetylated α-, β-, and γ-cyclodextrins

Triacetyl α-cyclodextrin, triacetyl β-cyclodextrin and triacetyl γ-cyclodextrin were tested as possible hydrophobic carriers to prolong the release of hydrophilic teicoplanin (TCP). Physical–chemical characterization of individual components, drug-carrier physical mixtures at 0.5, 0.67 and 0.75 mass fraction of carrier, and the respective interaction products by kneading or evaporative crystallization under microwave irradiation was carried out using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). In vitro drug release in pH 7.4 phosphate buffer at 37 °C was determined by intrinsic dissolution rate (IDR) measurements on non disintegrating compressed discs. Solid-state interactions of TCP with triacetyl α-cyclodextrin by evaporative crystallization and kneading and with triacetyl β-cyclodextrin by evaporative crystallization (probably resulting in carrier amorphization) were demonstrated. The role of carrier hydrophobicity, carrier mass fraction and preparation method of solid drug-carrier combinations on solid-state drug-carrier interactions and slowing down of TCP release was assessed. Modulation of drug release can be achieved using TCP-triacetyl γ-cyclodextrin combinations at 0.5 mass fraction of carrier.     

Light Element Analysis of Individual Microparticles Using Thin-Window EPMA

 The determination of the concentration of light elements, such as carbon, nitrogen and oxygen, in e.g. atmospheric aerosol particles is important to study the chemical behaviour of atmospheric pollution. The knowledge of low-Z element concentrations gives us information on the speciation of nutrients (species having nutritional value for plants) and toxic heavy metals in the particles. The capability of the conventional energy-dispersive EPMA is strongly limited for the analysis of low-Z elements, mainly because the Be window in the EDX detector hinders the detection of characteristic X-rays of light elements such as C, N, O and Na. WDS is suitable for analysis of light elements, but the measurement of beam sensitive microparticles requires the minimisation of the beam current and the measurement time. A semi-quantitative analytical method based on EPMA using an ultra-thin window EDX detector was developed. It was found that the matrix and geometric effects that are important for low-energy X-rays can be reliably evaluated by Monte Carlo calculations. Therefore, the quantification part of the method contains reverse Monte Carlo calculation done by iterative simulations. The method was standardised and tested by measurements on single particles with known chemical compositions. Beam-sensitive particles such as ammonium-sulphate and ammonium-nitrate were analysed using a liquid nitrogen cooled sample stage. The shape and size of the particles, which are important for the simulations, were determined using a high-magnification secondary electron image. Individual marine aerosol particles collected over the North Sea by a nine-stage Berner cascade impactor were analysed using this new method. Preliminary results on five samples and 4500 particles show that the method can be used to study the modification of sea-salt particles in the troposphere.     

Flow-through coulometry as a calibrationless method in inorganic trace analysis

The possibility of calibration-less determination of trace concentrations of some electrochemically active elements such as Ag, As, Cd, Hg, Pb, etc. by flow-through coulometry is described. The analyte species are collected quantitative-ly from the flowing sample solution on a porous working electrode made of vi- treous carbon particles set at either a constant potential or constant current. The deposit is stripped by a constant current in the next step and the correspond- ing electrical charge is measured and evaluated. The analyte concentration is calculated by making use of the com- bined Faraday’s laws of electrolysis. The method exerts detection limits about 1 μg/l or lower and a linear concentration range over 3 orders of magnitude.     

Definition of assigned values for proficiency tests in water analysis

The definition of an assigned value is usually achieved by calculating mean values from the data (with different methods) or by designating reference laboratories. Neither method is completely satisfactory. In this paper a new method is presented for the definition of the assigned value for spiked samples with an unknown content of the analyte in the matrix. The method consists of two parts. The first is the estimation of the assigned values from the spiked amounts and the content in the matrix, based on the results of reference laboratories. The other is the designation of these reference laboratories by comparing their results with the assigned values. Because each of these parts requires the other, an iterative procedure is necessary. As an example, the results of a proficiency test for the analysis of copper in wastewater are used to compare the calculated values with those from other methods, e.g., the Huber estimation. Received: 25 September 2000 Accepted: 9 December 2000     

Synthesis, structures, and properties of spiro[6-azaperimidine-2,4′-cyclohexa-2′,5′-dien]-1′-one derivatives

The reaction of 5-amino-4-chloroquinolines with 4-amino-2,6-di-tert-butylphenol yielded derivatives of spiro[6-azaperimidine-2,4′-cyclohexa-2′,5′-dien]-1′-one, which exhibit photo-and thermochromic properties in solutions. The structure of 2′,6′-di-tert-butyl-5,7,9-trimethylspiro[6-aza,-2,3-dihydroperimidine-2,4′-cyclohexa-2′,5′-dien]-1′-one was established by X-ray diffraction study. The ring-chain isomerization of 2′,6′-di-tert-butyl-5,7-dimethyl-and 2′,6′-di-tert-butyl-5,7,8-trimethylspiro[6-aza-2,3-dihydroperimidine-2,4′-cyclohexa-2′,5′-dien]-1′-ones was studied by dynamic NMR spectroscopy. Deceased. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2028–2034, November, 1997.