Cassette mutagenesis of Aspergillus awamori glucoamylase near its general acid residue to probe its catalytic and pH properties

Nine single amino add mutations in the active site of Aspergillusawamori glucoamylase were made by cassette mutagenesis to alterthe pH dependence of the enzyme and to determine possible functionsof the mutated residues. The Glul79-Asp mutation expressed inyeast led to a very large decrease in k_cat but to no changein K_m, verifying this residue's catalytic function. Aspl76-Gluand Glul80-Asp mutations affected K_m a more than k_cat, implyingthat Aspl76 and Glul80 are involved in substrate binding orstructural integrity. The Leul77-Asp mutation decreased k_catonly moderately, probably by changing the position of the generalacid catalytic group, and did not affect K_m. The Trpl78-Aspmutation greatly decreased k_cat while increasing K_m, showingthe importance of Trpl78 in the active site. Vall81-Asp andAsnl82-Asp mutations changed kinetk values little, suggestingthat Vall81 and Asnl82 are of minor catalytic and structuralimportance. Finally, insertions of Asp or Gly between residues176 and 177 resulted in almost complete loss of activity, probablycaused by destruction of the active site structure. No largechanges in pH dependence occurred in those mutations where kineticvalues could be determined, in spite of the increase in mostcases of the total negative charge. Increases in activationenergy of maltoheptaose hydrolysis in most of the mutant glucoamylasessuggested cleavage of individual hydrogen bonds in enzyme-substratecomplexes.     

Towards a super H2 producer: Improvements in photofermentative biohydrogen production by genetic manipulations

Photofermentative hydrogen production by purple non-sulfur bacteria is a potential candidate among biological hydrogen production methods. Hydrogen is produced under anaerobic conditions in light using different organic substrates as carbon source. The hydrogen evolution occurs mainly through the catalytic activity of the nitrogenases under non-repressive concentrations of ammonia. However, total hydrogen production is constrained due to several reasons in purple non-sulfur (PNS) bacteria, such as consumption of hydrogen by uptake hydrogenase, inefficient hydrogen production capacity of nitrogenase, limited electron flow to the nitrogenase, sensitivity of nitrogenase towards ammonia, etc. Hence, PNS bacteria need to be manipulated genetically to overcome these limitations and to make the process practically feasible. This review focuses on various approaches for the genetic improvement of biohydrogen production by PNS bacteria.     

A Novel Preconcentration Procedure Using Neutral Red as Ion-Pairing Reagent for Determination of Inorganic Dissolved Arsenic Species in Different Water and Beverages by Spectrophotometry

In the current study, a new cloud point extraction (CPE) procedure was developed for the separation and preconcentration of inorganic soluble As species, As(III), As(V), and total As in water and beverage samples. Selective ion-pairing complex of As(III) with Neutral red (NRH⁺) being a cationic phenazine-based dye in presence of citric acid at pH 2.0 was extracted into the surfactant-rich phase of octylphenoxypolyethoxyethanol (Triton X-114) from samples. After phase separation, the preconcentrated As(III) was determined by means of spectrophotometer at 542 nm. After optimization of the CPE conditions, a preconcentration factor of 50 and the detection and quantification limits of 1.44 and 4.8 μg L^?1 with a correlation coefficient of 0.9953 were obtained from the calibration curve constructed in the range of 5–1500 μg L^?1 for As(III). The precision of the method (as RSD) was in the range of 2.2–4.5 % (25, 100, and 750 μg L^?1, N?=?5). The As(V) contents of samples were calculated from the difference between As(III) and total As contents after the reduction of As(V) to As(III) with mixture of KI and ascorbic acid at HCl media. The method is very versatile and inexpensive because it exclusively used conventional UV–Vis spectrophotometry. The method was succesfully applied to the simultenous determination of inorganic arsenic species in different water and beverage samples. Its accuracy and precision were controlled by analysis of two certified reference materials (CRMs).

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Graphical Abstract Experimental steps of the CPE procedure for detection of As(III), As(V), and total As in beverage samples.

     

Probing a Device's Active Atoms

Materials science and device studies have, when implemented jointly as “operando” studies, better revealed the causal link between the properties of the device's materials and its operation, with applications ranging from gas sensing to information and energy technologies. Here, as a further step that maximizes this causal link, the paper focuses on the electronic properties of those atoms that drive a device's operation by using it to read out the materials property. It is demonstrated how this method can reveal insight into the operation of a macroscale, industrial‐grade microelectronic device on the atomic level. A magnetic tunnel junction's (MTJ's) current, which involves charge transport across different atomic species and interfaces, is measured while these atoms absorb soft X‐rays with synchrotron‐grade brilliance. X‐ray absorption is found to affect magnetotransport when the photon energy and linear polarization are tuned to excite Fe? O bonds parallel to the MTJ's interfaces. This explicit link between the device's spintronic performance and these Fe? O bonds, although predicted, challenges conventional wisdom on their detrimental spintronic impact. The technique opens interdisciplinary possibilities to directly probe the role of different atomic species on device operation, and shall considerably simplify the materials science iterations within device research.     

Fuzzy AHP-based decision support system for selecting ERP systems in textile industry by using balanced scorecard

An enterprise resource planning system (ERP) is the information backbone of a company that integrates and automates all business operations. It is a critical issue to select the suitable ERP system which meets all the business strategies and the goals of the company. This study presents an approach to select a suitable ERP system for textile industry. Textile companies have some difficulties to implement ERP systems such as variant structure of products, production variety and unqualified human resources. At first, the vision and the strategies of the organization are checked by using balanced scorecard. According to the company’s vision, strategies and KPIs, we can prepare a request for proposal. Then ERP packages that do not meet the requirements of the company are eliminated. After strategic management phase, the proposed methodology gives advice before ERP selection. The criteria were determined and then compared according to their importance. The rest ERP system solutions were selected to evaluate. An external evaluation team consisting of ERP consultants was assigned to select one of these solutions according to the predetermined criteria. In this study, the fuzzy analytic hierarchy process, a fuzzy extension of the multi-criteria decision-making technique AHP, was used to compare these ERP system solutions. The methodology was applied for a textile manufacturing company.     

A new approach based on artificial neural networks for high order multivariate fuzzy time series

Fuzzy time series methods have been recently becoming very popular in forecasting. These methods can be categorized into two subclasses that are univariate and multivariate approaches. It is a known fact that real time series data can actually be affected by many factors. In this case, the using multivariate fuzzy time series forecasting model can be more reasonable in order to get more accurate forecasts. To obtain fuzzy forecasts when multivariate fuzzy time series approach is adopted, the most applied method is using tables of fuzzy relations. However, employing this method is a computationally though task. In this study, we introduce a new method that does not require using fuzzy logic relation tables in order to determine fuzzy relationships. Instead, a feed forward artificial neural network is employed to determine fuzzy relationships. The proposed method is applied to the time series data of the total number of annual car road accidents casualties in Belgium from 1974 to 2004 and a comparison is made between our proposed method and the methods proposed by Jilani and Burney [Jilani, T. A., & Burney, S. M. A. (2008). Multivariate stochastic fuzzy forecasting models. Expert Systems with Applications, 35, 691–700] and Lee et al. [Lee, L.-W., Wang, L.-H., Chen, S.-M., & Leu, Y.-H. (2006). Handling forecasting problems based on two factors high order fuzzy time series. IEEE Transactions on Fuzzy Systems, 14, 468–477].     

Electrical properties of polyaniline‐manganese chloride composites

Electrical and morphological properties of Polyaniline (PANI) filled with various mass fractions of manganese chloride (MnCl₂) synthesized in aqueous hydrochloric acid (HCl) medium using ammonium persulphate as an oxidant were investigated. The sample morphology was characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Significant changes were observed in the morphology of the samples depending on the filler level. The direct current (dc) and alternating current (ac) electrical properties were investigated as a function of temperature. The dc conductivity decreased 72% with 10% filler level whereas ac conductivity has shown a 120% increase with 6% filler level at room temperature. It is shown that the alternating charge transport mechanism of the unfilled and filled polyaniline samples is consistent with correlated barrier hopping (CBH) model. Imaginary (M″) parts of electric modulus exhibited temperature‐dependent dielectric relaxation behavior for both filled and unfilled PANI samples. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers.     

Zinc and copper content in marine fish samples collected from the eastern Mediterranean Sea

Zinc and copper contents in the edible parts (muscle, fillet) of 49 commercially used fish species from the eastern Mediterranean Sea (Izmir Outer Bay, Homa Lagoon/Izmir and Mersin Bay) were determined by differential pulse stripping anodic voltammetry. In the sample preparation step, all frozen fish samples were lyophilized, milled in a ball mill and finally decomposed in an oxygen plasma ashing chamber. Among the three sampling locations, the highest zinc concentration was found in Mediterranean shad (Alosa fallax nilotica) from Izmir Outer Bay with 9.73 mg/kg wet weight and the highest copper content was found in derbio (Trachinotus ovatus) from Homa Lagoon with 1.14 mg/kg wet weight. The accuracy of the concentrations determined in this study was checked by the measurements of certified reference material no. 422 cod muscle from the Commission of the European Communities, Community Bureau of Reference. All zinc and copper concentrations observed in species of the eastern Mediterranean Sea showed that fish from this area are good sources of these essential elements.