Document Type : Research Paper
Environmental Engineering Department, Istanbul Technical University, 34469 Maslak, Istanbul, Turkey.
Shannon Applied Biotechnology Centre, Technological University of the Shannon:Midlands Midwest, Moylish Park, V94 E8YF Limerick, Ireland.
PhiTech Bioinformatics, 41400 Gebze, Kocaeli, Turkey.
Department of Bioengineering, Gebze Technical University, 41400 Gebze, Kocaeli, Turkey.
Economizing microalgal cultivation is a considerable milestone targeted by efforts put into microalgal biorefineries. In light of that, the present study was aimed to explore the potential of using anaerobic liquid digestate (ALD) as culture media to grow microalgae and compared it with three different synthetic media (i.e., N8, BBM, and M8) in terms of biomass yield, fatty acid composition, and nutrient utilization/recovery. Moreover, a mixed culture of wild-type microalgae was employed in this study owing to the ability of mixed cultures to survive extreme conditions, eliminating the risk of losing the culture easily, as it mostly happens with pure cultures. The highest nutrient yield coefficients were achieved when the mixed microalgae culture was cultivated in ALD, where the yield coefficient for nitrogen (YN) and yield coefficient for phosphorus (YP) were 10.7 mg biomass mg-1 N and 98 mg biomass mg-1 P, respectively. The highest lipid content (34%) and the highest concentrations of C16:0 (114 mg L-1) and C18:0 (60.9 mg L-1) were also recorded when the mixed microalgae culture was cultivated in ALD. Furthermore, the polyunsaturated fatty acids (PUFA) content also increased significantly in ALD, a beneficial phenomenon as PUFAs in microalgae allow them to adapt more effectively to extreme conditions. Based on the microbial community analysis performed using the multi-marker metabarcoding approach, Diphylleia rotans, Synechocystis PCC-6803, Cyanobium gracile PCC 6307, and Chlorella sorokiniana were identified as the most abundant species in the ALD growth. Overall, based on the findings of the present study, ALD could be used as a promising cultivation medium for microalgae, offering a process integration approach to combine anaerobic digestion and algae cultivation as an effective way to simultaneously treat the high-strength dark-colored ALD and valorize it into profitable byproducts.
- Anaerobic liquid digestate (ALD) was compared with synthetic media for microalgal cultivation.
- Microbial community analysis was performed with a multi-marker metabarcoding approach.
- ALD led to the highest lipid (34%) and C16:0 and C18:0 contents, 114 and 60.9 mg L-1, respectively.
- Microalgae`s PUFA content substantially increased for effective adaptation to ALD`s extreme conditions.
- Highest nutrient yield coefficients achieved when mixed microalgae culture was cultivated in ALD.