Characterization of a β-glucanase produced by Rhizopus microsporus var. microsporus, and its potential for application in the brewing industry

Background  

In the barley malting process, partial hydrolysis of β-glucans begins with seed germination. However, the endogenous 1,3-1,4-β-glucanases are heat inactivated, and the remaining high molecular weight β-glucans may cause severe problems such as increased brewer mash viscosity and turbidity. Increased viscosity impairs pumping and filtration, resulting in lower efficiency, reduced yields of extracts, and lower filtration rates, as well as the appearance of gelatinous precipitates in the finished beer. Therefore, the use of exogenous β-glucanases to reduce the β-glucans already present in the malt barley is highly desirable.     

Chromatographic performance of monolithic and particulate stationary phases. Hydrodynamics and adsorption capacity

Monolithic chromatographic support structures offer, as compared to the conventional particulate materials, a unique combination of high bed permeability, optimized solute transport to and from the active surface sites and a high loading capacity by the introduction of hierarchical order in the interconnected pore network and the possibility to independently manipulate the contributing sets of pores. While basic principles governing flow resistance, axial dispersion and adsorption capacity are remaining identical, and a similarity to particulate systems can be well recognized on that basis, a direct comparison of sphere geometry with monolithic structures is less obvious due, not least, to the complex shape of theskeleton domain. We present here a simple, widely applicable, phenomenological approach for treating single-phase incompressible flow through structures having a continuous, rigid solid phase. It relies on the determination of equivalent particle (sphere) dimensions which characterize the corresponding behaviour in a particulate, i.e. discontinuous bed. Equivalence is then obtained by dimensionless scaling of macroscopic fluid dynamical behaviour, hydraulic permeability and hydrodynamic dispersion in both types of materials, without needing a direct geometrical translation of their constituent units. Differences in adsorption capacity between particulate and monolithic stationary phases show that the silica-based monoliths with a bimodal pore size distribution provide, due to the high total porosity of the material of more than 90%, comparable maximum loading capacities with respect to random-close packings of completely porous spheres.     

Catalytic asymmetric carbohydroxylation of alkenes by a tandem diboration/Suzuki cross-coupling/oxidation reaction

[reaction: see text] Chiral nonsymmetric 1,2-diboron adducts are generated by catalytic enantioselective diboration. Oxidation of these adducts provides 1,2-diols in good yield. Alternatively, 1,2-diboron compounds may be reacted, in situ, with aryl halides wherein the less hindered C-B bond participates in cross-coupling. The remaining C-B bond is then oxidized in the reaction workup thereby allowing for net asymmetric carbohydroxylation of alkenes in a tandem one-pot diboration/Suzuki coupling/oxidation sequence.     

Stereochemical resolution of enantiomeric 2-aryl propionic acid non-steroidal anti-inflammatory drugs on a human serum albumin based high-performance liquid chromatographic chiral stationary phase

Summary The native enantioselectivity in binding of human serum albumin (HSA) towards 2-aryl propionic acid non-steroidal anti-inflammatory drugs (2-APA-NSAIDs, the profens) was found to be preserved when the protein was immobilized within a commercially available diol high-performance liquid chromatographic column. High capacity factors were obtained, reflecting the previously observed extensive binding of the 2-APA-NSAIDs to free HSA. The capacity factors were modified by the addition of octanoic acid to the mobile phase. Chiral resolution of the enantiomers of all nine 2-APA-NSAIDs studied was achieved. Preliminary studies show that in addition to being a useful chiral analytical tool for this therapeutically important series of compounds, the HSA chiral stationary phase may provide useful information on the affinity and binding mechanism of small molecules to HSA.     

Metal-organic approach to binary optical memory

Two new Ru(II) diimine chromophores, each containing a single photochromic dianthryl unit, have been prepared and characterized. The photoluminescence from the Ru(II) complexes is modulated by the photochromic action of the dianthryl species, which serves as a triplet energy transfer quencher in one photochromic state. The coupling of the dianthryl photochromic action to the Ru(II) complex emission permits nondestructive photoluminescence readout of binary information photochemically recorded on the molecular level. Luminescent images stored on polystyrene films that contain these molecules maintained their integrity for periods of months with no apparent degradation or variation in the image resolution, suggesting their durability for long-term storage in read-only memory applications.     

Mössbauer study of Brazilian soapstone

Steatite mineral rocks, soapstone, have been studied by X-ray diffraction, optical microscopic analysis (modal analysis), electron probe micro analysis and Mössbauer spectroscopy for characterization, mineral percentages and chemical composition. Mössbauer spectra show both, magnetic interactions corresponding to magnetite and doublets corresponding to talc. chlorite, dolomite and tremolite. The temperature dependence of the quadrupole splitting in dolomite has been explained in terms of crystal field interaction.     

Complexation behaviour of benzilmono(Iepidyl)hydrazone (BLH) toward bivalent metal ions: A potentiometric study

Potentiometric investigations on metal complexes of various bivalent metal ions, viz. UO₂(II), Cu(II), Ni(II), Co(II), Cd(II), Pb(II), Zn(II) and Mn(II) with benzilmonol(lepidy!)hydrazone (BLH) have been carried out at different ionic strengths and at different temperatures in order to determine stability constants of the complexes. Thermodynamic parameters ΔC, ΔH and ΔS have also been evaluated from temperature coefficient data. The effect of varying the dielectric constant of the medium on the stability constants of complexes has also been investigated at 30±0.5°C and μ = 0.1MNaCl. Thermodynamic stability constants and thermodynamic stabilization energies for the first transition metals have also been discussed.     

Cobalt(II) complexes of new biomimetic polydentate amide ligands. A spectroscopic,thermal and potentiometric study

Complexes of Co^II with N,N-bis-(3-carboxy-1-oxopropanyl)-1,2-ethylenediamine(L₁), N,N-bis-(3-carboxy-1-oxopropanyl)-1,2-phenylenediamine(L₂), N,N-bis-(2-carboxy-1-oxophenelenyl)-1,2-phenylenediamine(L₃) and N,N-bis-(3-carboxy-1-oxoprop-2-enyl)-1,2-phenylenediamine(L₄) have been prepared and characterized by elemental analysis, vibrational spectra, magnetic susceptibility measurements, electronic spectra and thermal studies. Stability constants of the complexes have been evaluated potentiometrically. Vibrational spectra indicate coordination of amide and carboxylate oxygens of the ligands along with two water molecules giving a MO₆ weak field octahedral chromophore. Electronic spectra support octahedral geometry around Co^II. The [Co(L₁)-(H₂O)₂] · 2H₂O complex has the maximum activation energy and [Co(L₃)(H₂O)₂] complex has the minimum activation energy. The order of stability constants of the Co^II complexes with various ligands is due to their -donor abilities.