Das Lehrgebiet BioVT publiziert zusammen mit der TH Bingen in Algal Research neueste Ergebnisse aus unserer Forschung im Bereich der phototrophen Biofilme.

Terrestrial cyanobacteria are phototrophic microorganisms, which grow embedded in a matrix of extracellular polymeric substances (EPS) as biofilms. To perform photosynthesis, cyanobacteria have developed, additionally to chlorophyll a and carotenoids, the so-called phycobilisomes, which consist of differently pigmented phycobiliproteins (PBPs). The production of natural dyes, pharmaceutical substances and their nutrient rich biomass makes cyanobacterial biofilms interesting research targets for industrial development. However, characterization of biofilms during cultivation implies several difficulties, since standard sampling applied in suspended cultures is not possible. The aim of this study was to find new possibilities for documenting biofilm growth. Therefore, two methods for non-invasive examination of phototrophic biofilms were combined. The terrestrial cyanobacteria Trichocoleus sociatus und Coleofasciculus chthonoplastes were cultivated surface-associated in an aerosol. Every three to four days biofilm thickness was measured using optical coherence tomography (OCT) and biofilm area using PAM fluorometry. Additionally, three replicates were harvested to determine biomass formation and pigment composition. According to our results, an increase of biomass, biofilm thickness and biofilm area was detected. The non-linear correlation between these parameters indicates an increase of biofilm area and thickness in the early phase of cultivation with a time-delayed biomass production. Hereby, possibly the proportion of EPS and biomass changed in the beginning in combination with biofilm spreading to increase the utilization of available light and aerosol components. Afterwards, biomass production was increased. Concerning pigment composition in the course of cultivation, for T. sociatus all PBPs were degraded, whereas in C. chthonoplastes an increase of all PBPs was measured. This can be explained with the role of PBPs for photosynthesis but as well as nitrogen storage, which is adjusted strain dependent. Summarizing, the shown methods are suitable for phototrophic biofilm characterization in a small scale. This allows the examination of cyanobacteria and a valuation of their suitability for possible production processes.

J. Stiefelmaier, D. Strieth, S. Di Nonno, N. Erdmann, K. Muffler, R. Ulber; Characterization of terrestrial phototrophic biofilms of cyanobacterial species; Algal Research, https://doi.org/10.1016/j.algal.2020.101996