| Abstract [eng] |
Cyanobacteria are photosynthetic microorganisms widely distributed around the world. In water, cyanobacteria can live in large colonies and create water blooms. Over the last decades, the presence of wild cyanobacterial blooms has also been reported in the Curonian Lagoon. Recent reports indicate that priority should be given to the removal of wild cyanobacterial blooms from the Curonian Lagoon as a management measure. In this study, the utilization of wild cyanobacteria as a potential source of high added products is reported. Lipophilic products from wild cyanobacteria was isolated from Curonian Lagoon by supercritical carbon dioxide extraction (SFE-CO2) and the yield, under optimal conditions, was compared with conventional Soxhlet extraction. Under optimal conditions (42.5 MPa, 55 ºC and 120 min), SFE-CO2 yielded 4.43 g/100 g DW of non-polar extract, showing 20% higher extraction efficiency at 3-fold lower extraction time as compared to the conventional Soxhlet extraction. The SFE-CO2 extract under optimal conditions was also evaluated by determining fatty acids, tocopherols and in vitro antioxidant activity. Results showed that it was rich in α-linolenic acid (27% of total fatty acids) and α-tocopherol (293 μg/g extract). Phycobiliproteins from wild cyanobacteria was isolated by several traditional extraction methods, of which the most effective was homogenization (one cycle, 30 min, 30 ºC), but after combining traditional methods with ultrasound assisted extraction (UAE) the freeze-thaw extraction with liquid nitrogen combined with UAE had the highest yield of phycobiliproteins (139.28 mg/g DW) under optimal conditions (one cycle of freeze-thaw and 99 % of amplitude, 9.39 min of UAE). The antioxidant activity of phycobiliproteins extracts was evaluated by in vitro methods. 8 Central composite design (CCD) and response surface methodology (RSM) were employed to optimize SFE-CO2, phycobiliproteins extractions parameters (temperature, pressure, amplitude and time) to obtain high yield extracts. Biorefinery was performed by removal of lipophilic fraction using SFE-CO2 or solid liquid extraction (SLE) with hexane, and by removal of phycobiliproteins using homogenization combined with UAE, and then performing accelerated solvent extraction (ASE) to extract the remaining materials by polarity. The extracts yield after ASE from fresh wild cyanobacterial biomass was 5.9 and 2.8 times higher than extracts yield after ASE and after SFE with phycobiliproteins removal and extracts yield after ASE and after SLE with phycobiliproteins removal, respectively. The ASE and SLE extracts from fresh cyanobacterial biomass was also evaluated by determining fatty acids and all ASE extracts was evaluated by determining in vitro antioxidant activity. Results of fatty acids detection showed that the most abundant fatty acid was α-linolenic acid: 225.86 mg/g in ASE extract with hexane at 55 ºC (32 %), 260.85 mg/g in ASE extract with hexane at 70 ºC (34 %) and 430 mg/g in SLE extract (36 %). All these extracts showed higher yield of α-Linolenic acid comparing with SFE-CO2 or Soxhlet extracts. Thus, SFE-CO2, phycobiliprotein extractions and ASE methods could be utilized to valorize wild cyanobacteria into high-added value products with various industrial applications. |
