Mixed-trophies two species biofilms driven by Cyanobacteria for biotechnnological applications

 

Despite photo-biocatalysis developing remarkably and the huge potential of photoautotrophic microorganisms for eco-efficient production scenarios, photo-biotechnology is still in its infancy. The lack of scalable photo-bioreactors that provide efficient light transmission, CO₂ supply, and O₂ degassing and thus enable high cell densities (HCD), constitutes a key bottleneck, especially if cost-sensitive bulk chemicals are the product of choice. Commercialized tubular photo-bioreactors with 100 to 600 mm inner diameter offer a surface area to volume ratio (SA/V) of over 100 m² m^-3 enabling the efficient capturing of incident solar radiation.¹ Here we introduce a new generation of photo-bioreactors based on capillary biofilm reactors. The biofilm is composed of two strains, namely the photoautotrophic strain Synechocystis sp. PCC 6803 and the chemoheterotrophic strain Pseudomonas taiwanensis VLB120, which serves as a biofilm supporter strain. Pseudomonas sp. is lowering the pO₂ in the system, which otherwise would toxify the Cyanobacteria. Furthermore, it produces extrapolymeric substances (EPS) and produces a kind of seeding layer promoting the attachment of Synechocystis sp.. Synechocystis sp. on the other hand produces organic compounds and oxygen consumed by Pseudomonas sp. The system is run completely without any organic carbon source.

Depending on the functionalities engineered into the biofilm forming organisms, these systems can be used for biotechnological applications. Here, we will present data on the physiology of the mixed trophies biofilm, and the challenging conversion of cyclohexane to caprolactone, and further on to 6-hydroxyadipic acid, both being important monomers for Nylon production.

 

References

• [1] Posten, C. Eng. In Life Science. (2009) 9:165-177
• [2] Hoschek, A. et al Bioresource Technology. (2019) 282: 171-178

 

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