Michaela Dina Stanescu

New Potential Biocatalysts by Laccase Immobilization in PVA Cryogel Type Carrier

Laccases are enzymes belonging to the Oxidoreductases class. These enzymes may be good biocatalysts for different processes, at laboratory and industrial levels. A successful use at industrial scale demands a higher stability of the enzyme. As an easy way to obtain longer life biocatalysts, the immobilization process is recommended. Thus, the paper presents different ways of obtaining new biocatalysts by a laccase covalent immobilization on a macroporous carrier based on poly(vinyl alcohol) cryogel. Different procedures of covalent immobilization are described, the newly obtained biocatalysts being characterized. According to the experimental data, the stability of the immobilized enzyme increased and the pH profile changed, compared with those of the free enzyme.

Fully automated chip-based negative mode nanoelectrospray mass spectrometry of fructooligosaccharides produced by heterologously expressed levansucrase from Pseudomonas syringae pv. tomato DC3000.

Pseudomonas syringae pathovars possess multiple levansucrases with still unclear specific roles for bacteria. We have cloned and expressed three levansucrase genes, lsc1, lsc2 and lsc3, from P. syringae DC3000 in Escherichia coli. Levansucrases synthesize a high molecular weight fructan polymer, levan, from sucrose and in the case of some levansucrases, fructooligosaccharides (FOS) with potential prebiotic effects are also produced. The ability of purified Lsc3 protein of DC3000 to synthesize FOS was tested using prolonged incubation time and varied concentrations of sugar substrates. Thin-layer chromatography (TLC) analysis of reaction products disclosed formation of FOS from both sucrose and raffinose, revealing a new catalytic property for P. syringae levansucrases. In order to analyze Lsc3-produced FOS in underivatized form, we optimized a novel method recently introduced in carbohydrate research, based on fully automated chip-based nanoelectrospray ionization (nanoESI) high-capacity ion trap mass spectrometry (HCT-MS). Uding chip-based nanoESI MS in negative ion mode, FOS, with degrees of polymerization up to five, were detected in reaction mixtures of Lsc3 with sucrose and raffinose. For confirmation, further structural analysis by tandem mass spectrometry (MS/MS) employing collision-induced dissociation at low energies was performed. To validate the method, commercial inulin-derived FOS preparations Orafti P95 and Orafti Synergy1, which are currently used as prebiotics, were used as controls. By chip-based nanoESI HCT-MS, similar FOS distribution was observed in these reference mixtures. Thereby, the obtained data allowed us to postulate that FOS produced by the Lsc3 protein of P. syringae DC3000 may be prebiotic as well.

Ultrasound effect on dyeing wool fibers with two anthraquinone dyes

Environmental and quality demands generate new approaches for finding better solutions in textile dyeing. A less polluting and more ecological procedure has been investigated, on this purpose. This study reveals the influence of ultrasounds (US) on wool dyeing. It presents comparatively the dyeing results for two frequently used anthraquinone dyes, one reactive (CI Reactive Blue 19) and the other acid (CI Acid Blue 62), applied on wool fibers. The comparison between the classic and the US dyeing procedures was performed in terms of: dye bath exhaustion, wash fastness and the color analysis. The dye aggregation was evidenced through the visible spectra, and the effect of US in this respect, was underlined, especially for the acid dye case. For the reactive dye, the higher bath exhaustion in US dyeing conditions was explained.