The ecological role of poly-hydroxybutyrate in cyanobacteria

Circular economy and any form of sustainable society depends on the availability of renewable resources in high quantities. Agricultural production of industrial raw products is, for well known reasons, ethically questionable. Cultivation of phototrophic microorganisms (algae and cyanobacteria) does not provoke such conflicts, but is, compared with agriculture, a relatively new research segment and far less optimised. One of the promising product groups are the poly- hydroxalkanoates (PHA`s), native in bacteria and cyanobacteria and, when isolated, with properties and with a usability similar to conventional plastics. Besides possibilities and limits for a biotechnological mass production, understanding the biological and ecological meaning of this natural polymer demands for investigative research. While there are already some reports for heterotrophic bacteria available, very little is known about the possible functions and interactions of PHA`s in cyanobacteria. Our project conducts highly specialised methods for measurements of chemical, physical, morphological and molecular parameters with the exposure of cyanobacteria cells to favourable and unfavourable environmental conditions. Based on the collected data we expect to gain a deep insight into the cyanobacterial stress response in terms of PHA accumulation. The outcome is not only of academic interest, it is likely a valuable base for future process optimisation in cyanobacterial biotechnology.

Any form of sustainable society depends on the availability of renewable resources in high quantities - on energy as well as on biomass. The demand will increase in foreseeable future. Agricultural production of industrial raw products is, for well known reasons, ethically questionable. Cultivation of phototrophic microorganisms (algae and cyanobacteria) does not provoke such conflicts, but is, compared with agriculture, a relatively new research segment and far less optimised. One of the promising product groups are the poly-hydroxalkanoates (PHA's), natively occurring in bacteria and cyanobacteria and, when isolated, having properties similar to some conventional plastic types. Therefore, such a process is scientifically, technically and economically interesting. PHBecol investigated scientific aspects. Possibilities and limits for a biotechnological mass production depend on the reliable and reproducible behaviour of the microbes. Understanding the physiological and ecological meaning of this biological polymer synthesis for the producing cells demands for investigative research. While there are already quite some reports for heterotrophic bacteria available, very little is known about the possible functions and interactions of PHB, the dominant PHA variant in cyanobacteria. Our project has conducted highly specialised methods for measurements of chemical, physical, morphological and some molecular parameters for cyanobacteria cells which were exposed to favourable and unfavourable environmental conditions. Based on the collected data we gained some novel and surprising insights into the cyanobacterial stress response in terms of PHB, glycogen and photopigment accumulation. The outcome is first and foremost of academic interest, but it is most likely a valuable base for future process optimisation in cyanobacterial biotechnology.