Microbial community dynamics in industrial algae production systems

Microalgae are a promising feedstock for biofuel production with the potential to make a large impact on displacing fossil fuels. However, a major challenge is consistent and robust algae growth during the scale-up process in bioreactor systems. The scale-up process consists of elite algae strains such as Nannochloropsis salina, which start in small 5 mL culture and scale to dozens of 200 L cultures. Large cultures are often comprised of complex communities bacteria and are difficult to manage as specific bacteria can promote or reduce algae growth. For successful algae cultivation, we must develop a better understanding of system ecology . In this study, we characterized bacterial communities richness, phylogenetic distance, and composition within industrial algae bioreactors during the scale-up process, through time, and during different algae growth rates. We used QIIME to analyze sequence data and determined that microbial communities in small, medium and large cultures were significantly different based on the fraction of evolutionary history in a phylogenetic tree that is unique to one of the communities. Large systems contained richer bacterial communities compared to small cultures based on phylogenetic distance and OTU count. Additionally, a core bacterium within the Saprospirae class was found in 100% of samples, with an average relative abundance of 34.7% +/-14.6%. Also, we sampled poorly performing large cultures, which a Deltaproteobacteria (spirobacillales) was observed at high relative abundances. This is the first study to characterize bacterial communities during the scale-up process, setting a foundation for crop protection studies in algae systems.