R. De Philippis

Selectivity in the heavy metal removal by exopolysaccharide‐producing cyanobacteria

Aims:  The aim of this study was to assess the selective removal of Cu(II), Cr(III) and Ni(II) by strains of exopolysaccharide (EPS)‐producing cyanobacteria, and to investigate the interaction of sorption in solutions with multiple‐metals.

Capsular polysaccharides of cultured phototrophic biofilms.

Phototrophic biofilm samples from an Italian wastewater treatment plant were studied in microcosm experiments under varying irradiances, temperatures and flow regimes to assess the effects of environmental variables and phototrophic biomass on capsular exopolysaccharides (CPS). The results, obtained from circular dichroism spectroscopy and High Performance Liquid Chromatography, suggest that CPS have a stable spatial conformation and a complex monosaccharide composition. The total amount present was positively correlated with the biomass of cyanobacteria and diatoms, and negatively with the biovolume of green algae. The proportion of uronic acids showed the same correlation with these taxon groups, indicating a potential role of cyanobacteria and diatoms in the removal of residual nutrients and noxious cations in wastewater treatment. While overall biofilm growth was limited by low irradiance, high temperature (30°C) and low flow velocity (25 l h−1) yielded the highest phototrophic biomass, the largest amount of CPS produced, and the highest proportion of carboxylic acids present.

Optimization of copper sorbing–desorbing cycles with confined cultures of the exopolysaccharide‐producing cyanobacterium Cyanospira capsulata

Aim:  The aim of this study was to compare the copper removal capability of the exopolysaccharide‐producing cyanobacterium Cyanospira capsulata confined into various filtering devices and to assess its reuse for several metal sorbing‐desorbing cycles.

Leptolyngbya strains from Roman hypogea: cytochemical and physico-chemical characterisation of exopolysaccharides

Two strains of Leptolyngbya isolated from Roman hypogea were studied in order to characterise the ultrastructural features of the sheath and its composition in exopolysaccharides. Cytochemical stains used in light and transmission electron microscopy allowed detection of the presence of carboxylic groups within the sheath, composed by two different layers. The composition in monosaccharides of three fractions (released, hot and cold capsular polysaccharides) extracted from cultures was determined by reverse phase-high performance liquid chromatography, while the behaviour of the fractions at various pH values was studied by using the circular dichroism. The cytochemical and physico-chemical characterisation of exopolysaccharides should help both the conservation of lithic surfaces of artistic interest and the taxonomic identification of Leptolyngbya strains.

Gold biosorption by exopolysaccharide producing cyanobacteria and purple nonsulphur bacteria

This study was aimed at investigating the possible exploitation of phototrophic micro‐organisms for the removal and the recovery of Au from Au‐containing wastewaters deriving from a plating industry.

Effectiveness of Cyanothece spp. and Cyanospira capsulata Exocellular Polysaccharides as Antiadhesive Agents for Blocking Attachment of Helicobacter pylori to Human Gastric Cells

The effect of cyanobacterial polysaccharides (fromCyanothece spp. andCyanospira capsulata) on the binding ofHelicobacter pylori to gastric epithelial cells was evaluated. The antiadhesive action on Kato III and HeLa S3 human gastric cell lines was established.

Purple Bacteria: Electron Acceptors and Donors

Purple bacteria form a heterogeneous group of microorganisms capable of growing under anoxic conditions by anoxygenic photosynthesis. They can be divided into purple nonsulfur bacteria, which are able to grow both phototrophically and in darkness, and purple sulfur bacteria, all of them capable to grow in the light but only few of them in the dark. They are characterized by a remarkable complexity in the metabolism, most of them being able to grow switching from chemotrophy to phototrophy, from organotrophy to litotrophy, and from heterotrophy to autotrophy. In this article, the main electron acceptors and donors involved in the photosynthetic and in the respiratory electron transport chains are described, pointing out the crucial role of the quinone pool for the energetic processes in the cell.

Marine Cyanobacteria as a Potential Source of Biomass and Chemicals

The mass culture in sea-water of three different cyanobacterial strains isolated from marine and hypersaline environments is described. Biomass yields and efficiencies of light energy conversion are reported both for laboratory and outdoor cultures. Gross chemical composition, amino acid and fatty acid profiles of the biomasses produced outdoors indicate that these organisms present a good potential as food or feed supplements. The production of an extracellular polysaccharide in a culture of a fourth cyanobacterial strain is also reported.