Production stability and biomass quality in microalgal cultivation - Contribution of community dynamics

The prospect of using constructed communities of microalgae in algal cultivation was confirmed in this study. Three different algal communities, constructed of diatoms (Diatom), green algae (Green), and cyanobacteria (Cyano), each mixed with a natural community of microalgae were cultivated in batch and semi-continuous mode and fed CO₂ or cement flue gas (12-15% CO₂). Diatom had the highest growth rate but Green had the highest yield. Changes in the community composition occurred throughout the experiment. Green algae were the most competitive group, while filamentous cyanobacteria were outcompeted. Euglenoids, recruited from scarce species in the natural community became a large part of the biomass in semi-steady state in all communities. High temporal and yield stability were demonstrated in all communities during semi-steady state. Valuable products (lipids, proteins, and carbohydrates) comprised 61.5 ± 5% of ash-free biomass and were similar for the three communities with lipids ranging 14-26% of dry mass (DM), proteins (15-28% DM) and carbohydrates (9-23% DM). Our results indicate that culture functions (stability, biomass quality) were maintained while dynamic changes occurred in community composition. We propose that a multispecies community approach can aid sustainability in microalgal cultivation, through complementary use of resources and higher culture stability.