Search

Most photosensitizers (PS) suffer from a lack of water solubility and from a low selectivity toward tumor cells. Delivery systems using nanoparticles make it possible to improve PS water solubility, and also tumor targeting via the enhanced permeability and retention (EPR) effect. Among the organelles, mitochondria are attractive target sites for drug-delivery strategies since they perform a variety of key cellular processes. Our study was aimed at synthesizing nanoparticles consisting of xylan-carrying porphyrins attached to a triphenylphosphonium moiety, in order to enhance the PDT effect through mitochondrial targeting. Hybrid nanoparticles were designed that consisted of a silica core coated with xylan substituted with porphyrin derivatives carrying a triphenylphosphonium moiety. These hybrid nanoparticles have been constructed, along with their counterparts devoid of silica core, taking into consideration the controversy surrounding the use of silica nanoparticles. Phototoxicity experiments, conducted against the HCT-116 and HT-29 colorectal cancer cell lines, showed that nanoparticles with porphyrins bearing a triphenylphosphonium moiety exhibited an enhanced photocytotoxic effect in comparison with free porphyrin or nanoparticles with porphyrins without the triphenylphosphoniummoiety. [ABSTRACT FROM AUTHOR]

The properties of cellulase and xylanase enzyme complexes formed in the culture fluid of T. harzianum UzCF-28 local fungal strain selected by screening from cellulose-degrading micromycetes have been studied. These enzymes showed their maximum activities in the pH range of 4.0-9.0: at pH 5.0 endo-1,4-β-glucanase and xylanase had maximum activities of 3.8 and 11.5 units /ml, respectively, while exo-1,4-β-glucanase - 2,92 units/ml at pH 5.5. 50°C was found to be the optimum temperature for these enzymes. Incubation time for endo-1,4-β-glucanase and xylanase enzymes was 30 min, while it was 60 min for exo-1,4-β-glucanase enzyme. Optimum concentration of substrates for endo-1-4-β-glucanase and xylanase enzymes was 1%, while it was equal to 50 mg for exo-1,4-β-glucanase (filter paper). At 60°C the activities of exo-1,4-β-glucanase and endo-1,4-β-glucanase enzymes decreased sharply and began to inactivate. It was found that xylanase was relatively thermostable among the enzymes; keeping its 43% activity at 70°C. [ABSTRACT FROM AUTHOR]

Among hemicellulases, xylanases are catalysts of considerable interest so as fundamental than applied point of view. However,it is paradoxical to note that the high cost of their production limits their use on a large scale. The use of purified xylan as culturesubstrate increases the production cost of the enzyme. Consequently, for commercial applications, it is advisable to developprocesses starting from inexpensive substrates. The purpose of this study is to optimise xylanases production in solid-statefermentation based on agricultural residues. The strain is Penicillium canescens 10-10c, selected in our laboratory for his abilityto produce xylanase activity free of cellulase. Assays concern optimization of different culture parameters in order to developin the future a solid-state fermentation reactor with soya oil cake. These parameters are: medium composition, temperatureincubation, induction and repression mechanisms. Soya oil cake in pellets (size > 10 mm) gave a higher enzymatic activity.Great volume of culture medium reduced the enzymatic production. The presence of lactose, saccharose or starch of corn hasa positive effect on the production of xylanase while the presence of xylose, mannose, galactose, arabinose, cellobiose andpectin or methylcellulose reduces the production of xylanase. The sources of phosphorus (di-potassic and di-sodic) enhancexylanase production. The enzymatic production obtained in Erlenmeyer flasks (250 ml) after 7 days incubation at 30°C isabout 14 000 U.g-1 of carbon source. The nature of inoculum affects the enzymatic productivity. Indeed, better productivitywas obtained with inoculation by solid preculture (956 U.g-1 per day) than liquid preculture (473 U.g-1 per day) and sporessuspension (383 U.g-1 per day). These observed enzymatic activity levels are higher than those related in the literature, whichshows all the potentialities of this strain and this technique for the production of xylanase and allow to develop our solid-statefermentation bioreactor.

Copyright of Biotechnologie, Agronomie, Societe et Environnement is the property of Les Presses Agronomiques de Gembloux and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)