Polyculture of marine algae: Best combination for biomass, biochemical, and biodiesel properties

Overyielding in polyculture systems suggests a potential for greater productivity than that observed in monocultures. Optimized algal polyculture combinations can significantly enhance biomass production and yield valuable biochemicals. The study tested seven different treatments of Nannochloropsis oculata, Chlorella sp., and Dunaliella tertiolecta in different ratios T1: (1:1:1), T2: (1:1:2), T3: (1:2:1), T4: (2:1:1), T5: (1:2:2), T6: (2:2:1), and T7: (2:1:2), respectively, under different photoperiods to assess the best combination for biomass, biochemical, and biodiesel properties. The results showed that under a 12:12 h light:dark photoperiod, T7 had the highest lipid and protein contents. There were also higher degrees of unsaturation in treatments 3, 6, and 7, whereas treatments 1, 2, and 4 had higher values for low carbon fuel standard and cold filter plugging point. Under a 16:8 h photoperiod, T3 had the highest total number of cells, T1 had the highest lipid level, and T3 had the highest protein level. Treatments 2 and 3 had significantly higher iodine values than the others, whereas T3 and T6 had higher cetane numbers. The results indicate that the highest protein and lipid levels were obtained in T3 under a 16:8 h photoperiod, whereas T1 had its highest protein and lipid levels during a 12:12 h photoperiod. Additionally, the highest biomass and mono-unsaturated fatty acids were observed in T3 under a 16:8 h photoperiod, and there were no significant differences in saponification values between treatments. Based on these findings, we recommend conducting algal polyculture with T3 (1:2:1) under a 16:8 h light:dark photoperiod to achieve optimal biomass production, higher protein, lipid, and mono-unsaturated fatty acid levels.