Detection of Bioactive Exometabolites Produced by the Filamentous Marine Cyanobacterium Geitlerinema sp.

Marine cyanobacteria are noted for their ability to excrete metabolites with biotic properties. This paper focuses on such exometabolites obtained from the culture of the marine filamentous cyanobacterium Geitlerinema sp. strain, their purification and subsequent analyses. By this means the recoveries of the active compounds, a prerequisite for properly determining their concentration, are quantified here for the first time. We demonstrate a new procedure using Amberlite XAD-1180 resin in combination with the eluent isopropanol for extraction of the culture media and gas chromatography as simplified chemical analysis. This procedure reduced necessary bacteria cultivation time (from 150 to 21 days) at low volumes of culture media (300 mL) required for identification of two selected bioactive compounds: 4,4′-dihydroxybiphenyl and harmane

KINETIC MODELLING OF METHYLENE BLUE DYE ADSORPTION ON CORN COBS IN STATIC AND DYNAMIC MODES

The purpose of this work was to study the removal of methylene blue (MB) from aqueous solutions by adsorption on corn cobs in static and dynamic modes. This agricultural by-product was first characterized and then a series of experiments was conducted to highlight the effect of different operating conditions on the adsorption capacity. Batch experiments revealed that adsorption of MB on corn cobs is affected by too acidic medium. Equilibrium data were represented well by a Langmuir isotherm equation with maximum adsorption capacity of 40 mg/g. RL values obtained at different dye concentration indicate that the sorption of MB on corn cobs is favorable. The second-order kinetic model describes perfectly adsorption kinetic data and adsorption may be controlled by external mass transfer followed by intra-particle diffusion mass transfer. The effectiveness of corn cobs biomass in the removal of methylene blue (MB) dye from its aqueous solution was tested by a fixed-bed column adsorption study. The results of dynamic mode were then modelled using Thomas and Yoon-Nelson equations. The results demonstrated that corn cobs are suitable for removal of MB from water using batch as well as fixed bed sorption system

Bacterial phylotypes associated with the digestive tract of the sea urchin Paracentrotus lividus and the ascidian Microcosmus sp

We used sequencing and phylogenetic analysis of PCR-amplified 16S rRNA genes from bacteria that are associated with the esophagus/pharynx, stomach and intestine of two marine sympatric invertebrates but with different feeding mechanisms, namely the sea urchin Paracentrotus lividus (grazer) and the ascidian Microcosmus sp. (suspension feeder). Amplifiable DNA was retrieved from all sections except the pharynx of the ascidian. Based on the inferred phylogeny of the retrieved sequences, the sea urchin's esophagus is mainly characterized mostly by bacteria belonging to alpha-, gamma-Proteobacteria and Bacteriodetes, most probably originating from the surrounding environment. The stomach revealed phylotypes that belonged to gamma- and delta-Proteobacteria, Verrucomicrobia and Fusobacteria. Since the majority of their closest relatives are anaerobic species and they could be putative symbionts of the P lividus stomach, in which anaerobic conditions also prevail. Seven out of eight phylotypes found in the sea urchin's intestine belonged to sulfate reducing delta-Proteobacteria, and one to gamma-Proteobacteria, with possible nutritional activities, i.e. degradation of complex organic compounds which is beneficial for the animal. The bacterial phylotypes of the ascidian digestive tract belonged only to the phyla of Actinobacteria and Proteobacteria. The stomach phylotypes of the ascidian were related to pathogenic bacteria possibly originating from the water column, while the intestine seemed to harbour putative symbiotic bacteria that are involved in the degradation of nitrogenous and other organic compounds, thus assisting ascidian nutrition

Boundary control of nonlinear elastic systems

This paper presents a design of boundary controllers for global stabilization of nonlinear elastic systems, which cover nonlinear elastic strings and membranes, under external bounded forces. The boundary controllers guarantee exponential convergence of the unique system solution to a ball centered at the origin. The Faedo–Galerkin approximation method is used to prove existence and uniqueness of the solution of the closed-loop system. The control design is based on the Lyapunov direct method, Gronwall’s, Poincare’s, and Holder’s inequalities, and Sobolev embedding theorems. Simulations illustrate the effectiveness of the proposed controllers