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. 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). Levan production kinetics was determined and compared between different bacteria types.

Nowadays, levan synthesis and its biocatalysis is a step claiming attention due to its promising uses in biomedical field. Levansucrase, as the enzyme responsible of levan biocatalysis is studied in this work concerning sequence homology, signal peptide, metal binding, etc. More than 650 different levansucrase sequences were studied and many interesting results were obtained such as phylogenetic trees and conserved residues that could be essential for biocatalysis machinery. Moreover, a review of levan applications in biomedicine and health field was made. It is showed the advances in applications such as a film agent, a carrier for drug delivery systems, an anti-inflammatory compound or its potential use for functional food as prebiotic.

An environmentally friendly technique was used to produce levan-capped silver nanoparticles of about 30 nm (with a loading of 30%) that showed bactericide effect, for E. coli and B. subtilis. That effect was mathematically studied with a dose-response model (lethal dose of 12.4 ppm and 6.8 ppm respectively). These silver nanoparticles were subsequently introduced in a gel to create a silver release system with bacteria inhibition activity. Silver release from the gel and its bactericidal activity was theoretically studied to develop a unique model that is able to predict accurately both silver release and lethal dose for any type of bacteria. This model will be useful for performing predictions for future silver in gel applications.