Periodic harvesting of microalgae from calcium alginate hydrogels for sustained high-density production.

High-density biomass production is currently only realized in biofilm-based photobioreactors. Harvest yields of whole biofilms are self-limited by daughter-upon-parent cell growth that hinders light and leads to respiratory biomass losses. In this work, we demonstrate a sustainable multi-harvest approach for prolonged generation of high-density biomass. Calcium-alginate hydrogel cultures loaded with Synechococcus elongatus PCC 7942 achieved production densities comparable to that of biofilms (10