Fig. 1 shows the results for the two strains at the six different tested ratios and controls at 750 nm while Fig. 2 summarizes the results by showing the percentage flocculation efficiencies for the two strains at each ratio. At the ratio of 1:1, harvest was slow and incomplete by 120 h (57% Kossou-4; 62% Overjuyo-3), while the control treatment showed slow growth over the 120 h (Fig. 2a). In contrast, at PRX-08066 A. fumigatus/B. braunii ratio of 1:10, the harvest was largely completed by 12 h with 93% of Kossou-4 and 95% of Overjuyo-3 being harvested ( Fig. 1 and Fig. 2b). A similar trend was observed at a ratio of 1:20 (92–94% of algae harvested), 1:30 (87–90% of algae harvested) and 1:40 (96–97% of algae harvested) ( Fig. 1 and Fig. 2c, d and e). However at a ratio 1:50, the harvest was slower and efficiency declined to 35% for Kossou-4 and 45% for Overjuyo-3 ( Fig. 1 and Fig. 2f). In terms of efficient use of fungus, a ratio of 1:40 was selected as the optimal ratio for harvesting from 500 l-scale studies as proteins resulted in the highest harvesting percentage ( Fig. 2e). OD measurements at 680 nm also confirmed that the ratio of 1/40 was the best for harvesting (data not shown). The successful co-pelletization at a 1:40 ratio demonstrated that this is a feasible approach with a relatively small (and therefore economic) volume of fungi resulting in an efficient flocculation of microalgae. Since there was little difference between the results for the two strains, it appears likely that this approach could be applied to other B. braunii strains.