Co-cultivation strategies and their impact on microalgal biomass composition

Microalgae are microorganisms capable of accumulating metabolites such as carbohydrates, lipids, proteins, pigments and others throughout their growth. These metabolites have various applications in the biotechnology field. Cultivating microalgae in a suitable nutrient-rich medium, such as Bold’s Basal Medium (BBM), supports optimal growth. Most past research on co-cultivation has focused on interactions between microalgae and fungi or microalgae and bacteria. However, studies on microalgae–microalgae co-cultivation remain limited, despite its potential to significantly enhance metabolite production. Therefore, the main objective in this study is to compare microalgae growth potential and biochemical compositions (lipids, carbohydrates, proteins and pigments) in monoculture and co-cultivation of microalgae. Two microalgae namely Chlorella sp. (UKM2) and Scenedesmus sp. (UKM9) were used. The results show that the maximum specific growth rate (μmax) for cocultivation was higher at 0.355 day-1, compared to 0.314 day-1 and 0.230 day-1 for UKM2 and UKM9 in monoculture, respectively. The results on the metabolites showed that lipid compounds were highly produced by monoculture UKM2 (2.981 g/L), followed by co-culture (2.698 g/L) and monoculture UKM9 (1.3 g/L). Next, in terms of carbohydrate content, no significant difference was found in all experiments. Meanwhile, for pigment profiles including total chlorophyll and carotenoids, UKM2 in monoculture exhibited the highest concentrations. The interaction between microalgae in co-culture resulted in the highest protein production, reaching 4.39 g/L, compared to monocultures of UKM2 and UKM9. In conclusion, co-cultivation resulted in high growth rate corresponding to the enhanced protein production; certain metabolites were more abundantly produced from monoculture conditions. Moving forward, optimizing protein extraction methods is essential to maximize yield from microalgae co-cultures. Additionally, exploring strains compatibility and refining co-cultivation parameters will be key in advancing the production of targeted metabolites in microalgae biotechnology.