Effect of high pH on growth of Synechocystis sp. PCC 6803 cultures and their contamination by golden algae (Poterioochromonas sp.)

摘要

Culturing cyanobacteria in a highly alkalineenvironment is a possible strategy for controlling contaminationby other organisms. Synechocystis PCC 6803cells were grown in continuous cultures to assess theirgrowth performance at different pH values. Light conversionefficiency linearly decreased with the increase in pH andranged between 12.5 % (PAR) at pH 7.5 (optimal) and decreasedto 8.9 % at pH 11.0. Photosynthetic activity, assessedby measuring both chlorophyll fluorescence and photosynthesisrate, was not much affected going from pH 7.5 to 11.0,while productivity, growth yield, and biomass yield on lightenergy declined by 32, 28, and 26 % respectively at pH 11.0.Biochemical composition of the biomass did not change muchwithin pH 7 and 10, while when grown at pH 11.0, carbohydratecontent increased by 33 % while lipid content decreasedby about the same amount. Protein content remained almostconstant (average 65.8 % of dry weight). Cultures maintainedat pH above 11.0 could grow free of contaminants (protozoaand other competing microalgae belonging to the species ofPoterioochromonas).