This work aimed to characterize two native microalgal strains newly isolated from South Mediterranean areas and identified as Chlorella sorokiniana ES3 and Neochloris sp. AM2. The growth properties and biochemical composition of these microalgae were evaluated in different culture media (Algal, BG-11, f/2, and Conway). Among the tested media, nitrate- and phosphate-rich Algal medium provided the maximum biomass productivities (85.5 and 111.5 mg l(-1) day(-1) for C. sorokiniana and Neochloris sp., respectively), while the nitrate- and phosphate-deficient f/2 medium resulted in the highest lipid productivities (24.1 and 35.8 mg l(-1) day(-1) for C. sorokiniana and Neochloris sp., respectively). The physiological state of both microalgae was investigated under different light and temperature levels using the pulse amplitude-modulated fluorometry. The better photosynthetic efficiency of C. sorokiniana was obtained at 23 °C with a light saturation of 156 μE m(-2) s(-1), while that of Neochloris sp. was achieved at 15 °C with a light saturation of 151 μE m(-2) s(-1). The analysis of fatty acid profile and biodiesel parameters revealed that C. sorokiniana, cultivated in Algal and f/2 media, can be considered as a suitable candidate for high-quality biodiesel production.
Research background. Microalgae represent an emergent sustainable source of bioactive compounds such as antioxidants, vitamins, minerals, and polyunsaturated fatty acids that can ameliorate the nutritional characteristics of foods. The biochemical composition of microalgae could be modulated by varying the culture conditions to enhance the accumulation of biomolecules of interest. The aim of this work is to optimise the nutri-functional properties of two microalgae with potential utility for food-application.
Experimental approach. Nannochloropsis gaditana.L2 and Chlorella sp.SM1 were screened for growth, biochemical composition, and radical scavenging activity employing four different growth media (Algal, BG-11, f/2, and Conway) with different nutrients composition. Additionally, the feasibility of using Chlorella sp.SM1 cultivated in BG-11 medium, in a Mediterranean under-investigated dairy product “ricotta cheese” and its effect on the sensory attributes was investigated.
Results and conclusions. Nitrate- and phosphate-rich media (BG-11 and Algal) enhanced the biomass productivity. However, the highest lipid productivity (23.10 mg/(L·day); 11.86 mg/(L·day) for SM1 and L2 respectively) and carbohydrates content (34.79 %; 44.84 % for SM1 and L2 respectively) were obtained with the nitrate-deficient f/2 medium. Regardless of the used medium, the lipidic profile of Chlorella sp.SM1 and Nannochloropsis gaditana.L2 remained adequate for different applications with the presence of C16-18 as main fatty acid (>50 %). Significant increase in oleic acid (C18:1) content was recorded in response to nitrogen deficiency, being the highest in SM1 in f/2 medium (34 %). Nitrogen deficiency was also found to enhance phenolic compounds (48.8 GAE/(mg/g); 35.1 GAE/(mg/g) for SM1 and L2 respectively) and carotenoids contents (2.2 mg/g; 2 mg/g for SM1 and L2 respectively). Due to its interesting antioxidant potential, Chlorella sp.SM1 was used to enrich the ricotta cheese product at different concentrations (0.2 %, 1 % and 1.5 %). The sample with 0.2 % was found to give the most appreciated product.
Novelty and scientific contribution. This study permitted the production of an innovative ricotta cheese using Chlorella, as a functional ingredient, without altering the manufacturing diagram while maintaining acceptable sensorial characteristics. The biochemical composition of the used strains varied depending on the culture media’s composition, which permitted the accumulation of phytonutrients of interest.
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