Screening of two terrestrial cyanobacteria for biotechnological production processes in shaking flasks,bubble columns,and stirred tank reactors

Terrestrial cyanobacteria are rarely used for biotechnological processes, although they show great potential in terms of value-added substances. Cyanobacteria from arid habitats are of particular interest because they tolerate higher temperatures and feature a different product spectrum compared with their aquatic counterparts. In addition, terrestrial cyanobacteria may represent an interesting source of pharmaceutical products. To investigate the future use of these organisms in biotechnological processes, the growth rates of Trichocoleus sociatus (formerly Microcoleus sociatus) and Nostoc muscorum were examined using three different cultivation systems: shaking flasks, bubble columns, and stirred tank reactors. Parameters including pH, temperature, CO₂ level, and power dissipation were investigated quantitatively in the three systems for their impact on growth rate. The highest growth rate of the terrestrial cyanobacteria could be achieved in a stirred tank reactor under enriched CO₂ concentration. In this system, the growth rate was 1.15 day^-1?±?0.08 (2 % vol.) for T. sociatus and 0.72 day^-1?±?0.22 (5 % vol.) for N. muscorum, based on dry weight. Furthermore, a basic mathematical model was created as an add-on to predict growth rates of terrestrial cyanobacteria based on their dependency on temperature, pH, and substrate concentration, in general. This model was used to estimate growth of N. muscorum in stirred tank reactor experiments with an accuracy of 98.8 % and with 75 % accuracy for T. sociatus.