WP1. Cultivation, modelling and optimization of algae growth and biomass processing by conventional and unconventional extraction methods
In the first stage, an experimental model of cultivating an algal strain (Dunaliella Salina) was developed in order to select microalgae with a high content of oil and carotenoids. At the end of the exponential growth period, the algal biomass was centrifuged and lyophilized. The algal biomass separated from the culture medium was further processed to obtain the lipid fraction and carotenoid content.
WP2. Microalgal biomass processing by conventional and unconventional extraction methods
During this stage, experimental models were developed for the cultivation of 3 algal strains, in order to select microalgae with a high oil and carotenoid content. At the end of the exponential growth period, the algal biomass was centrifuged and lyophilized. The algal biomass separated from the culture medium was further processed to obtain the lipid fraction and carotenoid content. Due to the very good results obtained, the following two algal strains were selected for further experiments: Porphyridium Purpureum and Chlorella Vulgaris. The algal biomass was further processed by conventional and unconventional extraction methods in order to extract the lipid fraction and pigments (carotenoids). The ultrasonic assisted extraction (UAE) method was used to obtain high extraction yields of carotenoids and lipids. To optimize the extraction parameters different values of intensity (from 60 to 100%), ethanol concentration (25 and 70%), solvent composition (ethanol and hexane concentration ratio to volume ratios of 1: 2; 2: 1 and 1.25 to 1)) and the biomass: solvent ratio (w / v (1: 4 – 1: 8)) were studied. The results obtained can be used for the accumulation and selective extraction of saturated and polyunsaturated fatty acids using food grade solvents. These products can be used in many applications, such as in the food industry and as a lipid supplement. The antioxidant activity of 3 samples was studied: algal biomass of Chlorella vulgaris and Porphyridium purpureum and exopolysaccharides. All 3 samples showed a dependence of the oxidizing activity with the concentration, the highest value being recorded at the highest concentration of 100 μg / ml.
WP3. Processing the interest compounds extracted from microalgae biomass to synthesize value added chemicals
In the last stage, the synthesis of ethyl ester of polyunsaturated fatty acid (PUFAEs) and levulinic acid from carbohidrate fraction and the thermal conversion of de-oil biomass into biochar was followed. A preliminary step to obtaining PUFAEs was the esterification of free fatty acids from microalgae oil with ethanol in the presence of new solid acid catalysts. Parameter optimization (molar ratio oil:alcohol, reaction time, catalyst mass) were obtained using experimental design software. The new efficient solid-acid catalysts prepared was characterized using adequate technics. The transesterification step of pre-treated algae oil with ethanol was realized using a heterogeneous catalyst with hydrotalcite structure. The distribution of PUFAEs and the reaction yield was measured using GC–MS/MS TRIPLE QUAD (Agilent 7890 A).
Levulinic acid (LA) was obtained from the exocarbohydrate fraction from algae biomass, using a stainless steel autoclave purchased in the previous step. For LA synthesis it was tested the same sulfated ferromagnetic acid catalyst prepared previously.
The thermal conversion of de-oil biomass into biochar was performed into the Continuous Flow Tubular Reactor. The major activity was the parameters optimisation (temperature, oxygen concentration and time) in order to obtain a biochar with adsorption properties (characteristics as
porosity, high specific surface area, cation exchange capacity). The porosity, as well as the specific pore area will be was determined by Nova surface area and pore size device. The biochar adsorption capacity for inorganic compounds (e.g Ca, Na, N and P) will be assessed by the application of extended Freundlich isotherm.
