Antibacterial and antiviral metabolites from cyanobacteria: Their application and their impact on human health

Bacterial and viral infections pose a direct threat to human health due to the increase of drug-resistant and novel pathogenic strains. Natural products represent a prolific source of bioactive metabolites, which have been exploited for their therapeutic effects. In particular, cyanobacteria were identified as important producers of secondary metabolites possessing antibacterial and antiviral activities, among others. A meta-analysis indicated that some natural product classes target bacteria or viruses exclusively. This result also applied for some cyanobacterial species that were identified to produce only antibacterial or antiviral compounds. Furthermore, cyanobacteria represent a promising host for bio-production due to their ability to perform photosynthesis and their low-cost production requirements. This review highlights antibacterial and antiviral compounds isol isolated from cyanobacteria and the biotechnological application of these organism

Reliability approach in spacecraft structures

This paper presents an application of the probabilistic approach with reliability assessment on a spacecraft structure. The adopted strategy uses meta-modeling with first and second order polynomial functions. This method aims at minimizing computational time while giving relevant results. The first part focuses on computational tools employed in the strategy development. The second part presents a spacecraft application. The purpose is to highlight benefits of the probabilistic approach compared with the current deterministic one. From examples of reliability assessment we show some advantages which could be found in industrial applications

Cyanobacteria for PHB production

The study carried out during the present Ph.D. program aimed at investigating the PHB production process in autotrophic cultures of cyanobacteria. The work was carried out at the Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione Industriale of the University of Naples ‘Federico II’ and at Molecular Microbial Physiology Group of the Swammerdam Institute for Life Sciences in Universiteit van Amsterdam. The activities were articulated according to three paths: i) the characterization of PHB production process as regards kinetics and yields using different growth media characterized by different nitrate concentration and screening cyanobacteria strains; ii) the characterization of the PHB production process by cyanobacteria according to kinetic models; iii) the development of genetic engineering approach on cyanobacteria to improve PHB production. 1)Selection of the optimal growth media to produce PHB and screening of cyanobacteria strains: characterization in terms of kinetics and yields. The study was aimed at the assessment of both the kinetics and the yields of the cell growth and PHB produced during the growth on different growth media characterized by different nitrate concentrations: BG11 (optimal nitrate concentration), BG1/2 (half of optimal nitrate concentration), BG1/4 (one fourth of the optimal nitrate concentration) and BG0 (nitrogen-starved conditions). Batch tests were focused on the preliminary characterization of the PHB production process from cyanobacteria with the aim of highlighting the relevant features of the process. Synechocystis PCC6803 was growth as model strains on the different culture media. The investigation was carried out in photobioreactors using CO2 as carbon source. The best media for PHB production was BG1/2 (half of optimal nitrate concentration). Five cyanobacteria strains were screened using BG1/2 medium, to select a high PHB producer: Synechocystis PCC6803, Synechocystis aquatilis, Synechocystis fuscopigmentosa, Synecoccoccus nidulans and Chlorogloeopsis Fritshii. 2)Characterization of the PHB production process: kinetic models. An adequate kinetic model to describe the PHB production process is a key issue to address the conditions to maximize the PHB fraction in the cell. A kinetic model of PHB production by Synechocystis PCC6803 from CO2 was proposed using the biochemical networks simulator COPASI. Data form growth tests under dynamic light system (light/dark cycle) carried out at different initial nitrate concentration were used to assess the kinetic and stoichiometric parameters of the proposed model. Two types of cells were considered in the cultures: growing cells (X), which are able to grow, and PHB producing cells (XPHB). The specific velocity (kT) of XPHB formation was considered dependent from the initial concentration of nitrate. The proposed model includes the nitrate and phosphate utilization rate, the PHB production rate, the cell growth and lysis rate. The model adequately predicted the experimental data, indeed the square correlation coefficient of metabolite concentrations, calculated by comparing experiments and simulations, ranged between 0.81 and 0.99. 3)Genetic modified cyanobacteria strain to improve PHB production. In this study Synechocystis sp. PCC6803 was genetically modified with aim to improve PHB production from CO2. Seven mutant strains were created by single and combined mutations: deletion of phosphotransacetylase (pta); the deletion of acetyl-CoA hydrolase (ach); the overexpression of phosphoketolase (xfpk). The tests were carried out on BG11 medium. The mutant strain that gave best performance on BG11 medium was tested on optimized medium (BG1/2 medium)