A semi-continuous process based on an ePBR for the production of EPS using Trichocoleus sociatus

Biodiversity forms the basis for a large pool of potential products and productive organisms offered by terrestrial cyanobacteria. They are stuck together by EPS (extracellular polymeric substances) that can obtain antiviral, antibacterial or anti-inflammatory substances. Most stress conditions, e.g. drought, induce the production of protective EPS or biotechnological-products for pharmaceutical application. However, the growth of a phototrophic biofilm is limited under submerged conditions. Therefore, a semi-continuous process to produce EPS by cyanobacteria was developed in an aerosol-based ePBR (emerse photobioreactor) that imitates the natural habitat of terrestrial cyanobacteria. The process consists of a growth-phase (biomass production), followed by a dry-phase (EPS-production) and a consecutive extraction. The EPS-productivities of Trichocoleus sociatus (ranging from 0.03 to 0.04gL^-1d^-1) were 32 times higher than described in topic-related literature. In comparison to submerge cultivations in shaking flasks, the EPS-productivities were sevenfold higher. To ensure that the extraction solvent has no influence on cell viability, a cell-vitality-test was performed. However, no statistically significant difference between the amount of living and dead cells before and after the extraction was detected. A bioactivity assay was then performed to identify antimicrobial activity within EPS extracts from emerse and submerge cultivations. The EPS revealed an antibacterial effect against gram-negative bacteria (E. coli) which was two times higher than EPS from a submerged cultivation.