Mastery of Cultural Conditions and Physico-chemical Properties Improves the Production and the Catalytic Efficiency of bglG

Stachybotrys microspora is a filamentous fungus secreting multiple β-glucosidases. Two of them were characterized. The third one, named bglG, was also characterized and used for various investigations. The current work undertakes the plausible role played by some cultural conditions and physico-chemical properties to improve bglG time course synthesis and also its catalytic efficiency. Indeed, bglG time course synthesis is slightly affected by light, but it is clearly affected by aeration and presence of baffle. On the same case, optimization of substrate and enzyme concentration contributes to the improvement of the catalytic efficiency of bglG. This biocatalyst tolerates a high ionic strength during its activity assay; β-mercaptoethanol increases the enzymatic rate. BglG has the capacity to hydrolyse efficiently oleuropéin, with a recovery of 88 %.     

Synthesis,crystal structure,thermal analysis,and electrical properties of bis tetrapropylammonium hexachloro-dizincate compound

The present paper accounts for the synthesis, crystal structure, differential scanning calorimetry, vibrational study, and electrical properties of the [N(C₃H₇)₄]₂Zn₂Cl₆ compound. The latter is crystallized at room temperature in the triclinic system ( $ P\overline{1} $ space group) with the following unit cell parameters: a?=?13.736(2)Å, b?=?17.044(3)Å, c?=?17.334(2)Å, α?=?68.30(2)°, β?=?75.14(2)°, and γ?=?84.93(3). The atomic arrangement can be described by alternating organic and inorganic layers parallel to the (001) plan, made up of [N(C₃H₇)₄]⁺ groups and [Zn₂Cl₆]^2? dimers, respectively. In crystal structure, the inorganic layer, built up by Zn₂Cl₆ dimers, is connected to the organic ones through van der Waals interaction in order to build cation–anion–cation cohesion. The infrared and Raman studies confirm the presence of the organic group tetrapropylammonium and the Zn₂Cl₆ anion. Concerning the differential scanning calorimetry, it revealed two reversible solid–solid phase transitions of first order: at 327/324 K and 347/343 K (heating/cooling). Besides, the impedance spectroscopy study, reported in the sample, reveals that the conduction in the material is due to a hopping process. Regarding the temperature dependence of the dc conductivity, it suggests Arrhenius type: σ _dc T?=?B ?exp(?E _a /kT). The tetrapropylammonium cations appeared to be the most sensitive to the phase transition.     

Self-assembling and self-limiting monolayer deposition

Effects of spatial ordering of molecules on surfaces are commonly utilized to deposit ultra-thin films with a thickness of a few nm. In this review paper, several methods are discussed, that are distinguished from other thin film deposition processes by exactly these effects that lead to self-assembling and self-limiting layer growth and eventually to coatings with unique and fascinating properties and applications in micro-electronics, optics, chemistry, or biology. Traditional methods for the formation of self-assembled films of ordered organic molecules, such as the Langmuir-Blodgett technique along with thermal atomic layer deposition (ALD) of inorganic molecules are evaluated. The overview is complemented by more recent developments for the deposition of organic or hybrid films by molecular layer deposition. Particular attention is given to plasma assisted techniques, either as a preparative, supplementary step or as inherent part of the deposition as in plasma enhanced ALD or plasma assisted, repeated grafting deposition. The different methods are compared and their film formation mechanisms along with their advantages are presented from the perspective of a plasma scientist. The paper contains lists of established film compounds and a collection of the relevant literature is provided for further reading.     

The Constitutive Production of Pectinase by the CT1 Mutant of Penicillium Occitainis is Modulated by pH

The aim of the present study was to investigate pectinases production by CT1 mutant of Penicillium occitanis on glucose based media. Two main groups of pectinases were followed: lyases (pectin and pectate lyases) and hydrolases (polygalacturonases and polymethylgalacturonases). When cultivated in different liquid media, where either the starting glucose concentration or the nature of nitrogen sources used was varied, the CT1 mutant secreted either lyases or hydrolases. In fact, the pH of these various media seemed to correlate with the activity produced: The lyases were highly and exclusively produced at neutral or alkaline ambient pH, whereas hydrolases were highly produced on acidic ambient pH. Such conclusion was confirmed by following pectinase production in the same culture medium (with the same glucose concentration and the same nitrogen source) set at two initial pH of 4 and 7. Altogether, these results suggest that the pectinases control by PacC signaling pathway of P. occitanis should resemble to that of Aspergillus and its ability to “activate the expression of alkaline-expressed genes and repress acid-expressed genes” remains intact in the CT1 over-producing and constitutive strain. Enzymes produced at acidic pH (hydrolases) and at neutral pH (lyases) were applied in the hydrolysis of orange peel and gave results comparable to commercial enzymes.     

Investigations on Hydrolytic Activities from Stachybotrys microspora and Their Use as an Alternative in Yeast DNA Extraction

Stachybotrys microspora is a filamentous fungus characterized by the secretion of multiple hydrolytic activities (cellulolytic and non-cellulolytic enzymes). The production of these biocatalysts was studied under submerged culture using glucose, cellulose, and wheat bran as carbon sources. Endoglucanases, pectinases, xylanases, β-glucanases, chitinases, and proteases were induced on cellulose-based medium and repressed on glucose in both strains with higher amounts produced by the mutant. β-glucosidases were roughly equally produced by both strains under glucose and cellulose conditions. The yield of chitinases, β-glucanases, and proteases produced by Stachybotrys strains was as much higher than the commercialized lysing enzyme called “zymolyase,” currently used in yeast DNA extraction. In this context, we showed that S. microspora hydrolases can be successfully applied in the extraction of yeast DNA.     

Gly311 residue triggers the enantioselectivity of Staphylococcus xylosus lipase: a monolayer study

Using emulsified triacylglycerols, we have shown recently [Mosbah et al., 2007, submitted for publication] that amino acid residue G311 of Staphylococcus xylosus lipase (SXL) is critically involved in substrate selectivity, pH and temperature dependency. Using the monomolecular film technique, we show in the present study that the four single mutants of this residue (G311L, G311W, G311D, and G311K), interact efficiently with egg-phosphatidyl choline (egg-PC) monomolecular films, comparably to the wild-type (G311). A critical surface pressure (pi(c)) of about 25 mN/m was obtained with the SXL wild-type (SXL-WT) and its mutants. These results support our conclusion that the G311 residue is not involved in the interfacial adsorption step of SXL. A kinetic study on the surface pressure dependency, stereoselectivity, and regioselectivity of SXL-WT and its G311 mutants was also performed using optically pure enantiomers of diacylglycerols (1,2-sn-dicaprin and 2,3-sn-dicaprin) and a prochiral isomer (1,3-sn-dicaprin) spread as monomolecular films at the air-water interface. Our results indicated that the mutation of one single residue at position 311 affects critically the catalytic activity, the stereo- and the regioselectivity of SXL. As previously observed with emulsified substrates [Mosbah et al., 2007, submitted for publication] we observed that an increase in the size of the 311 amino acid side chain residue was accompanied by a decrease of lipase activity measured on dicaprin monolayer. We also noticed that the substitution of G311 by a basic or acidic residue (G311K and G311D), induces a significant shift of the pH optimum from 8 to 9.5 or from 8 to 6.5, respectively.     

Chemical composition and biological activities of essential oils of Pinus patula

Essential oils isolated from needles of Pinus patula by hydrodistillation were analyzed by gas chromatography-flame ionization detection (GC-FID) and gas chromatography mass spectrometry (GC-MS). Thirty-eight compounds were identified, representing 98.3% of the total oil. The oil was rich in monoterpene hydrocarbons (62.4%), particularly alpha-pinene (35.2%) and beta-phellandrene (19.5%). The in vitro antifungal assay showed that P. patula oil significantly inhibited the growth of 9 plant pathogenic fungi. The oil, when tested on Sinapis arvensis, Lolium rigidum, Phalaris canariensis and Trifolium campestre, completely inhibited seed germination and seedling growth of all species. Our preliminary results showed that P. patula essential oil could be valorized for the control of weeds and fungal plant diseases.     

Purification and Biochemical Characterization of a Highly Thermostable Xylanase from <Emphasis Type="Italic">Actinomadura</Emphasis> sp. Strain Cpt20 Isolated from Poultry Compost

An extracellular thermostable xylanase from a newly isolated thermophilic Actinomadura sp. strain Cpt20 was purified and characterized. Based on matrix-assisted laser desorption–ionization time-of-flight mass spectrometry analysis, the purified enzyme is a monomer with a molecular mass of 20,110.13 Da. The 19 residue N-terminal sequence of the enzyme showed 84% homology with those of actinomycete endoxylanases. The optimum pH and temperature values for xylanase activity were pH 10 and 80 °C, respectively. This xylanase was stable within a pH range of 5–10 and up to a temperature of 90 °C. It showed high thermostability at 60 °C for 5 days and half-life times at 90 °C and 100 °C were 2 and 1 h, respectively. The xylanase was specific for xylans, showing higher specific activity on soluble oat-spelt xylan followed by beechwood xylan. This enzyme obeyed the Michaelis–Menten kinetics, with the K _m and k _cat values being 1.55 mg soluble oat-spelt xylan/ml and 388 min⁻¹, respectively. While the xylanase from Actinomadura sp. Cpt20 was activated by Mn²⁺, Ca²⁺, and Cu²⁺, it was, strongly inhibited by Hg²⁺, Zn²⁺, and Ba²⁺. These properties make this enzyme a potential candidate for future use in biotechnological applications particularly in the pulp and paper industry.