Refereed article in compilation book (A3)

Photosynthetic microorganisms as biocatalysts

List of AuthorsNikkanen Lauri, Hubacek Michal, Allahverdiyeva Yagut

PublisherDe Gruyter

Publication year2021

Book title *Photosynthesis: Biotechnological Applications with Microalgae

Title of seriesDe Gruyter STEM

Start page257

End page278






Photosynthetic cell factories based on living algae or cyanobacteria havevast potential for carbon-neutral production of desired compounds, and can thusbecome integral components of sustainable bioeconomies. Immobilization of thephotosynthetic cells in solid-state matrices provides significant advantages overconventional suspension cultures such ashigher cell densities, higher volumetricproductivity, enhanced light distributionthrough elimination of self-shading, aswell as lower energy and water consumptionthrough lower volumes and unnecessityof stirring. State-of-the-art matrices of, for example, nanocelluloseprovide possibilitiesfor highly tailored porous and hierarchical architectures mimicking the anatomy of theplant leaf, where light distribution, water use and gas exchange can be optimized. Inaddition to immobilization, the yields of photosynthesis-based biocatalyst platformsmay be improved by redirecting photosynthetically produced reducing power towardthe desired reactions via bioengineering ofthe electron transport pathways in algaeand cyanobacteria. In their natural environments where light, temperature and nutrientavailability can fluctuate dramatically, photosynthetic organisms protect the integrityof the photosynthetic apparatus by several alternative electron transport (AET) path-ways that can in effect function as release valves for excessive reducing power. AETpathways include the Mehler-like reaction catalyzed by flavodiiron proteins, cyclic elec-tron transport around photosystem 1, as well as terminal oxidases in the thylakoidmembrane. Modification or removal of AET pathways has potential to enhance thechanneling of electrons towardthedesiredbioproductionreaction(s). Other possibleapproaches include modification of the photosynthetic electron transport chain itself,as well as the introduction of heterologous electron sinks in the cell or chloroplast. Op-timization of production conditions may also have a substantial impact on the yield ofbioproduction. For example, the productionof bio-hydrogen in algae has recently beenenhanced by applying a pulse-illumination protocol that prevents the activation ofcompetitive electron sinks. Ultimately, biotechnologically optimized photosyntheticwhole-cell biotransformation platforms can be combined with tailored solid-state im-mobilization matrices for efficient and sustainable solar-driven production.

Last updated on 2021-08-11 at 14:28