Effect of bacteria type and sucrose concentration on levan yield and its molecular weight.

BACKGROUND: Levan has been traditionally produced from microorganism. However, there is a continuous effort in looking for new strains that improve levan production yield and uses alternative sugar sources for growth. Despite having a wide range of data about levan yield, there are not papers which allow controlling molecular weight, and that plays an essential role for further applications. RESULTS: The effect of the sucrose concentration on levan yield (and its molecular weight) from Bacillus atrophaeus and Acinetobacter nectaris (Gram positive and Gram negative respectively) was studied in this work. It was found that A. nectaris growth (from 3 to 1.5 g L-1 in 40 h) and its levan production (from 3 to 1.5 g L-1) decreases by increasing sucrose concentration (best results at a concentration of 120 g L-1) whereas B. atrophaeus growth (3.5 g L-1 in 30 h) and its levan production (also 3.5 g L-1) were not affected by modifying that parameter. Levan molecular weight from A. nectaris decreases by increasing sucrose concentration (from 8000 to 2000 kDa) whereas levan molecular weight from B. Atrophaeus remains always around 50 kDa. By performing a kinetic study, it was shown that A. nectaris growth follows a substrate-inhibition model, whereas Monod equation provided a good fit for B. atrophaeus growth. Finally, wastes from orange juice industry were used as a medium culture to cultivate those microorganism, obtaining good results with B. atrophaeus (growth 3 g L-1 in 30 h). CONCLUSIONS: Levan production kinetics was determined and compared between different bacteria types.

Development of a nanoparticle system based on a fructose polymer: Stability and drug release studies.

New drug delivery systems (DDSs) with levan or its carboxymethylated form, as carriers, and 5-fluorouracil as a drug, are produced in this work. Levan is obtained after cultivating A. nectaris and polymer nanoparticles are created in water by a self-assembled process. The effect of pH and the ionic strength on polymer nanoparticles aggregation is studied. Basic pHs produces a particle size between 300 and 400nm with a Z-potential around -20mV because a basic medium promotes repulsion forces. DDSs of 300-400nm and a Z-potential about -25mV are prepared by taking advantage of the amphiphilic properties of the levan. The drug is bound to either levan or carboxymethyllevan surfaces by electrostatic interactions, obtaining the best results at basic pHs. 45-70% of the drug is released from the levan in 23h depending on the pH preparation, whereas only a low percentage of the drug is released from the carboxymethyllevan.

Understanding and optimizing the addition of phytohormones in the culture of microalgae for lipid production.

Some studies have described the use of phytohormones in microalgal culture for the production of biodiesel or selected fatty acids. However, no study has determined the amount of phytohormones that maximizes lipid yield. We determined the optimal concentration of auxins and gibberellins (which is between 40 and 60 µM) in two strains (Scenedemus abundans and Chlorella ellipsoidea) suitable for biodiesel production. More than 3-fold increment was reached with S. abundans and near 7-fold increment with C. ellipsoidea. Furthermore, this work suggests that the improved growth of the microalgae in the presence of the phytohormones was due to a reduction in the level of reactive oxygen species (ROS) in the cells. An economic analysis showed that, due to its low cost, auxin offers a positive cost-benefit balance and therefore could be used at large scale. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1203-1211, 2016.

Effect of nitrogen source on growth and lipid accumulation in Scenedesmus abundans and Chlorella ellipsoidea.

Discovering microalgae strains containing a high lipid yield and adequate fatty acid composition is becoming a crucial fact in algae-oil factories. In this study, two unknown strains, named Scenedesmus abundans and Chlorella ellipsoidea, have been tested for their response to different nitrogen sources, in order to determine its influence in the production of lipids. For S. abundans, autotrophic culture with ammonium nitrate offers the maximum lipid yield, obtaining up to 3.55 mg L(-1) d(-1). For C. ellipsoidea, heterotrophic culture with ammonium nitrate has been shown to be the best condition, reaching a lipid production of 9.27 mg L(-1) d(-1). Moreover, fatty acid composition obtained from these cultures meets international biodiesel standards with an important amount of C18:1, achieving 70% of total fatty acids and thus representing a potential use of these two strains at an industrial scale.

Immobilization of mesenchymal stem cells and monocytes in biocompatible microcapsules to cell therapy.

The aim of cell therapy is to replace, repair, or enhance the function of damaged tissues or organs. Several factors complicate the development of cellular therapies. Of primary importance is protection of the implanted cells from the host's immune system. Cells are encapsulated in selectively semipermeable and biocompatible membranes that block entry of immune mediators but allow outward diffusion of active molecules produced by the cells. The immobilization of mesenchymal stem cells and monocytes, in micrometric (30-60 microm) alginate-barium microcapsules based on atomization processes, has been achieved successfully. This size is necessary to the administration of microcapsules via injection (Hamilton syringe with a needle size of 100 microm) and aerosol. Microencapsulated cells survive at least 2 weeks after preparation in vitro.