Earlier this year, I wrote about the production of prodigiosin based on work by Ricardo Pereira, PhD, and Carla de Carvalho, PhD, both at the University of Lisbon’s Instituto Superior Técnico. Beyond being a red dye for fabrics, prodigiosin can also be used in making drugs to treat bacterial infections, cancer, and more. Still, Pereira and de Carvalho keep working on the key challenge behind using prodigiosin: getting enough of it.
Prodigiosin comes from the marine bacterium Serratia rubidaea, which can be collected from hydrothermal vents in shallow water. No commercial bioprocessor can rely on capturing enough S. rubidaea from nature. Instead, samples of this bacteria must be collected and then expanded in a lab. Nonetheless, hitting production levels of prodigiosin is difficult.
Recently, Pereira and de Carvalho described a new approach to producing prodigiosin. The key was keeping in mind where S. rubidaea lives, which is in the intertidal zone. From low to high tide, these bacteria experience large changes in temperature and nutrients, such as oxygen.
Pereira and de Carvalho looked carefully at the environmental conditions where they collected the bacteria, which they described as “a semi-enclosed rock pool” off São Miguel Island in the Azores. At this site, the water is only a few meters deep and the topology keeps waves small. With the bacteria living underwater in an area that experienced little wave-driven water movement, the environment included low levels of oxygen.
So, Pereira and de Carvalho collected S. rubidaea and grew it in stirred-tank reactors. As they described the conditions in the reactors: “The medium contained nutrients that allowed its proliferation in the ecological niche, and the conditions in the laboratory mimicked the abiotic conditions present during high and low tides, meaning periods of starvation and oxygen depletion during fermentation.” This approach increased the production of prodigiosin by 3.7-fold compared to growing the bacteria without such a strategy.
As Pereira and de Carvalho concluded: “This study thus indicates that by mimicking the conditions found at the isolation site during fermentation and by using analytical methods to assess cell physiological conditions, it is possible to significantly increase product yield.”