Immobilization of dextransucrase on functionalized TiO2 supports.

The TiO2 based hybrid supports with different functional groups (amino, glutaraldehyde or epoxy) were prepared and their influence on immobilization of dextransucrase (DS) was studied. Novel synthetic route for surface modification of TiO2 with amino and glutaraldehyde groups was developed taking advantage of charge transfer complex (CTC) formation between surface Ti atoms and salicylate-type of ligand (5­aminosalicylic acid (5-ASA)). The proposed coordination of 5-ASA to the surface of TiO2 powder and optical properties of CTC was presented. The pristine TiO2 and amino functionalized TiO2 have higher sorption capacity for DS (12.6 and 12.0mgg-1, respectively) compared to glutaraldehyde and epoxy activated supports (9.6 and 9.8mgg-1, respectively). However, immobilized enzyme to either glutaraldehyde or epoxy functionalized TiO2 have almost two times higher expressed activities compared to pristine TiO2 support (258, 235 and 142IUg-1, respectively). Thermal stability of enzyme immobilized on glutaraldehyde and epoxy functionalized supports was studied at 40°C, as well as operational stability under long-run working conditions in repeated cycles. After five cycles, DS imobilized on glutaraldehyde activated support retained almost 70% of its initial expressed activity, while, after five cycles, performance of DS immobilized on epoxy activated support was significantly lower (15%).

Interaction of amino acid-functionalized silver nanoparticles and Candida albicans polymorphs: A deep-UV fluorescence imaging study.

The interaction of the tryptophan functionalized Ag nanoparticles and live Candida albicans cells was studied by synchrotron excitation deep-ultraviolet (DUV) fluorescence imaging at the DISCO beamline of Synchrotron SOLEIL. DUV imaging showed that incubation of the fungus with functionalized nanoparticles results in significant increase in the fluorescence signal. The analysis of the images revealed that the interaction of the nanoparticles with (pseudo)hyphae polymorphs of the diploid fungus was less pronounced than in the case of yeast cells or budding spores. The changes in the intensity of the fluorescence signals of the cells after incubation were followed in [327-353nm] and [370-410nm] spectral ranges that correspond to the fluorescence of tryptophan in non-polar and polar environment, respectively. As a consequence of the environmental sensitivity of the silver-tryptophan fluorescent nanoprobe, we were able to determine the possible accumulation sites of the nanoparticles. The analysis of the intensity decay kinetics showed that the photobleaching effects were more pronounced in the case of the functionalized nanoparticle treated cells. The results of time-integrated emission in the mentioned spectral ranges suggested that the nanoparticles penetrate the cells, but that the majority of the nanoparticles attach to the cells' surfaces.

Sugar Beet Pulp as Leuconostoc mesenteroides T3 Support for Enhanced Dextransucrase Production on Molasses.

Sugar beet pulp (SBP) and molasses, as an agro industrial waste material, are produced in large amounts annually. Thus, a major challenge nowadays is to develop procedures that could increase the value of the generated waste. In this study, SBP as a support for cell immobilization and molasses as a source of nutrients were used for a dextransucrase (DS) production by Leuconostoc mesenteroides T3. The influence of SBP in native form (SBP-N) and after treatment with NaOH (SBP-NaOH) on DS production was investigated. The optimal medium composition for the maximum DS production was determined by varying the concentration of molasses, SBP, and sucrose. The maximum DS yield of 2.02 U/ml was obtained in the medium with 2.5 % of molasses, 2.5 % SBP-NaOH, and 4 % of sucrose concentration. Scanning electron microscopy (SEM) showed immobilization of Lc. mesenteroides T3 cells onto SBP-NaOH. According to the obtained results, the production of DS on molasses could be improved by using NaOH-treated SBP as a carrier for whole-cell immobilization. Our study reveals the basis for the development of process for DS production with additional reduction of expenses by using waste materials for obtaining the valuable biotechnological product.