Publikation: A new strategy for a combined isolation of EPS and pigments from cyanobacteria

Terrestrial Ccyanobacteria obtain their energy through photosynthesis. They live embedded in a matrix of extracellular polymeric substances (EPS) containing valuable products e.g. polysaccharides, lipids (fatty acids), proteins (amino acids) and antimicrobials. Besides chlorophyll-a (green pigment) and carotenoids (orange pigment), they developed light-absorbing compounds in form of accessory pigmentsof light-harvesting complexes, so-called phycobilisomes consisting of different phycobiliproteinsproteins (blue and pink pigments). The pigments and phycobiliproteins are of industrial interest as natural dyes. Up to now, cyanobacteria have been produced in submerged cultivation systems, which are suboptimal due to their nature to form biofilms on surfaces. Cultivation of cyanobacteria on a lab-scale Diverse biofilm reactors have been developed (on a lab-scale) to imitate their natural growth, resultsing in small amounts of biomass for biomass-characterisation. Especially the production of EPS and pigments production are indicators for the cell-condition.

Therefore, different EPS extraction methods were tested including the determination of inhibitory effects of extracts against Escherichia coli. Based on the best EPS extraction method a combined downstream processnew strategy for downstream processing (DSP) was developed to determine (i) EPS and the (ii) pigments (i) chlorophyll-a, and (ii) carotenoids and as well as the (iii) phycobiliproteins from only one sample. As a cyanobacterial model organisms, Trichocoleus sociatus, collected from a hyperarid habitat, and Nostoc flagelliforme was were used and DSP strategy was successfully transferred to two aquatic and two terrestrial cyanobacteria. . Four different EPS extraction methods were carried out. However, by combining heat and ultrasonication, highest yields of EPS could be achieved. Cell lysis caused by chemical or physical extraction methods could not be detected. However, the extracts showed differences in bioactivity whereby the inhibitory effect against Escherichia coli correlated with the extracted amount of EPS. After EPS extraction, eight variations of pigment extraction were tested to reach the highest possible yield. The best final DSP results were obtained usingincludes the following steps the following order: (i) lyophilizsing the biomass, followed by (ii) extraction of phycobiliproteins with cell disruption using 75 % filling degree (w/w) and a final (iii) chlorophyll-a and carotenoid extraction.

Journal of Applied Phycology (JAPH-D-19-00640R1); accepted paper