Microbial Resistance Mechanisms to the Antibiotic and Phytotoxin Fusaric Acid

Fusaric acid (FA) produced by Fusarium oxysporum plays an important role in disease development in plants, including cotton. This non-specific toxin also has antibiotic effects on microorganisms. Thus, one expects a potential pool of diverse detoxification mechanisms of FA in nature. Bacteria and fungi from soils infested with Fusarium and from laboratory sources were evaluated for their ability to grow in the presence of FA and to alter the structure of FA into less toxic compounds. None of the bacterial strains were able to chemically modify FA. Highly FA-resistant strains were found only in Gram-negative bacteria, mainly in the genus of Pseudomonas. The FA resistance of the Gram-negative bacteria was positively correlated with the number of predicted genes for FA efflux pumps present in the genome. Phylogenetic analysis of predicted FA resistance proteins (FUSC, an inner membrane transporter component of the efflux pump) revealed that FUSC proteins having high sequence identities with the functionally characterized FA resistance protein FusC or Fdt might be the major contributors of FA resistance. In contrast, most fungi converted FA to less toxic compounds regardless of the level of FA resistance they exhibited. Five derivatives were detected, and the detoxification of FA involved either oxidative reactions on the butyl side chain or reductive reactions on the carboxylic acid group. The production of these metabolites from widely different phyla indicates that resistance to FA by altering its structure is highly conserved. A few FA resistant saprophytic or biocontrol strains of fungi were incapable of altering FA, indicating a possible involvement of efflux transporters. Deployment of both efflux and derivatization mechanisms may be a common feature of fungal FA resistance.     

Modifizierung der integralen form der Mayo-Lewis-Gleichung zur berechnung der copolymerzusammensetzung bei der semikontinuierlichen polymerisation

Equations for the mathematical simulation of the semicontinuous copolymerization are proposed. With these equations it is possible to calculate the composition course of the monomer phase and of the just formed polymer, as well as the integral composition of the polymer as a function of conversion. The proposed relations form a system of differential equations, which are calculated numerically by stepwise integration. This calculation process is demonstrated using semicontinuous emulsion polymerization of the styrene/acrylonitrile system. The calculated relations show, that after a quasi-stationary phase has been reached, the polymerization ratio must be higher than the ratio of the monomer dosage.     

Polypropylene/polyethylene blends as models for high‐impact propylene–ethylene copolymers,part 1: Interaction between rheology and morphology

In this work, composition effects on interfacial tension and morphology of binary polyolefin blends were studied using rheology and electron microscopy. The amount of dispersed phase (5–30 wt %) and its type [ethylene–octene copolymer, linear low‐density polyethylene (LLDPE), and high‐density polyethylene] was varied, and the influence of different matrix materials was also studied by using a polypropylene homopolymer and a ethylene–propylene (EP) random copolymer. The particle size distribution of the blends was determined using micrographs from transmission electron microscopy (TEM). A clear matrix effect on the flow behavior could be found from the viscosity curves of the blends. Analyzing the viscosity of the blends applying the logarithmic mixing rule indicated a partial miscibility of the EP random copolymer with low amounts of the LLDPE in the melt. Micrographs from TEM also showed a clear difference in morphology if the base polymer is changed, with PE lamellae growing out of the inclusions or being present directly embedded in the matrix. To verify these findings, the interfacial tension was determined. The applicability of Palierne's emulsion model was found to be limited for such complex systems, whereas Gramespacher–Meissner analysis led to interfacial tensions comparable with those already reported in the literature. The improved compatibility when changing the matrix polymer from the homopolymer to the random copolymer allows the development of multiphase materials with finer phase structure, which will also result in improved mechanical and optical performance. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Wearable Displays for Everyone!

Spectacles is a hardware/software platform developed from off-the-shelf components and ready for market. It includes local computation and communication facilities, an integrated power supply, and modular system building blocks such as sensors, voice-to-text and text-to-speech components, localization and positioning units, and microdisplay units. Its see-through display components are integrated into eyeglass frames.     

Refolding of proteins in a CSTR

A model to predict refolding of proteins in a continuous stirred tank reactor (CSTR) was developed and compared to a batch refolding process with simple dilution of the protein in a stirred tank reactor. For experimental verification of the model a continuous refolding of a model protein (α-lactalbumin) was performed in a CSTR. The refolding process of denatured and fully reduced α-lactalbumin could be accurately predicted by a set of differential equations assuming a first order reaction rate for folding and a second order reaction rate for aggregation. The system composed of a CSTR with an additional diafiltration circuit for removal of denaturing agents from the feed solution and to maintain constant refolding conditions. Based on the folding kinetic the dynamic behavior of such a continuous refolding reactor was simulated under different operating conditions. It was shown that the refolding efficiency was higher compared to batch dilution under certain conditions, namely high residence times. The yield of refolded protein could further increased by recycling the outlet stream containing unfolded protein to the reactor entrance.     

Molecular weight distribution of poly(ethylene adipate) and its changes caused by aging

Precipitation fractionations of poly(ethylene adipate) were carried out by nonsolvent addition methods using chloroform as solvent and petroleum ether as nonsolvent. Seventy-five grams of the polyester was fractionated into 10 fractions by stepwise method and 35 g of the former was fractionated into nine fractions by triangle method. Number-average molecular weights were determined by ebullioscopic measurements with chloroform as solvent. Acid, hydroxyl, and saponification numbers were determined by analytical methods. It was proved that poly(ethylene adipate) contained considerable quantity of cyclic molecules (ca. 23 mol %). The molecular weight distribution curves of linear molecules constructed from the results of polyester fractionations were found to differ rather from distribution expected from the theory of kinetics of polycondensation and statistical theory. This discrepancy may be explained by higher reactivity of functional groups belonging to shorter molecular chains. It was found out that the aged poly(ethylene adipate) hydrolyzed to a great extent and practically contains no cyclic molecules. Molecular weight distribution of the aged poly(ethylene adipate) determined by GPC is very near to the theoretical “most probable distribution” derived for polycondensates.     

Alkaline hydrolysis of ethyl acrylate–acrylonitrile–divinylbenzene copolymer beads

This article deals with the alkaline hydrolysis of ethyl acrylate–acrylonitrile–divinylbenzene copolymer beads. Chemical changes during hydrolysis were evaluated by means of determination of total weight exchange capacity and of infrared spectroscopy. The influence of reaction temperature, concentration of the hydrolytic agent, degree of copolymers crosslinking as well as the influence of particle size upon the rate of hydrolysis were studied as a function of time. The mathematical and statistical calculations of experimental data were carried out. With respect to time dependence of hydrolysis of the copolymer functional groups, the average values of reaction rate constants as well as the values of assumed diffusion coefficients were calculated. The analysis is based on partial linearization of experimental results by means of semilogarithmic transformation. The empirical relations expressing dependences of reaction rate constants and of diffusion coefficients on conditions of hydrolysis were determined.