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Exploring the Potential of Algae-Bacteria Communities For Biotechnology



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Riseley, Anthony Shawn 


Microalgae are a large and diverse group of photosynthetic organisms ranging from prokaryotic cyanobacteria to eukaryotic algae spread across many phyla. Traditional algal biotechnology approaches have focused on growing algae in monoculture, in contrast to nature, where algae live in association with many other organisms. One association of interest is between the bacterium Mesorhizobium loti (Rhizobiales) and the green alga, Lobomonas rostrata deficient in the production of vitamin B12. The alga provides fixed carbon to the bacterium whereas the bacterium supplies vitamin B12 to the alga. In the course of a screen for bacterial mutants altered in the interaction, a novel symbiosis was serendipitously identified involving the non-Rhizobiales bacterium Rhodococcus erythropolis and L. rostrata. This novel interaction, together with interaction of the more industrially relevant Chlamydomonas reinhardtii strain was characterized. Nitrogen is a major limiting nutrient for industrial scale algal production. An alternative option to the Haber-Bosch process of synthesising and supplementing fixed nitrogen into media is to utilise nitrogen fixing bacteria capable of secreting fixed nitrogen into the media otherwise known as biofertilisation. Anabaena sp. PCC 7120 is a filamentous cyanobacteria that can fix its own nitrogen and engineered strains capable of releasing fixed nitrogen in the form of amino acids and ammonium were cultured with the industrially relevant Chlamydomonas reinhardtii metE—+ M. loti consortium and Chlorella vulgaris in nitrogen-free media. There are relatively few published studies investigating and outlining the challenges involved in scaling algae production from the laboratory through to pilot scale. Furthermore, these studies have typically focused on growing axenic cultures. The B12-dependent strain of C. reinhardtii metE— was grown in the presence of supplemented B12 and B12 producing M. loti at lab scale (50 mL), pre-pilot scale (10 L) and pilot scale (60 L). The growth efficiency as determined by growth rate, was measured and compared for both cultures at all scales.





Howe, Christopher


Algae-bacteria communities, Biotechnology, Genetic Engineering


Doctor of Philosophy (PhD)

Awarding Institution

University of Cambridge
Anthony S. Riseley received funding from the People Programme (Marie Curie Actions) of the European Union’s Seventh Framework Programme FP7/2007–2013/under Research Executive Agency grant agreement no. 317184