Starch productivity in cyclically operated photobioreactors with marine microalgae—effect of ammonium addition regime and volume exchange ratio

Abstract

Large-scale production of microalgal storage compounds will likely involve marine microalgae. Previously, we described a method to enrich microalgae with a high storage compound productivity from a natural inoculum. Here, this strategy was implemented under marine conditions in a sequencing batch reactor. The influence of the volume exchange ratio and the moment of ammonium addition in the day–night cycle on the storage compound productivity are described. Storage compound productivity was maximal if ammonium was supplied at the start of the dark period rather than the light period, irrespective of the volume exchange ratio. Increasing the volume exchange ratio from 33 to 50 % per cycle induced a decrease in storage compound production if ammonium was supplied in the light whereas the storage compound productivity was comparable when ammonium was supplied in the dark. The latter indicates a shift of cell division processes to the light period at increasing volume exchange ratio, although ammonium uptake completely occurred in the dark period.