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Background: This study aimed to maximize biomass concentration, biomass productivity and biochemical composition of the marine microalga Tetraselmis sp., Methods: In the current study, Box-Behnken Design was used to model the effect of NaNO 3 , NaH 2 PO 4 , metals and vitamins in the F/2 medium on the growth, total chlorophylls, carotenoids and starch contents. The total chlorophylls content was quantified by spectrophotometry. The FT-IR spectroscopy was used to estimate the biochemical compositions of Tetraselmis sp. grown under both optimized medium culture for starch production and standard culture medium., Results: Finalized NaNO 3 (1.76 mM), NaH 2 PO 4 (0.018 mM), metals (1500 μL.L -1 ) and vitamins (312.5 μL.L -1 ) concentrations, generated an increase in biomass concentration up to 5.72 g.L -1 which contributed to an increase about 2.4-fold than that of the standard conditions of biomass productivity (408.57 mg.L -1 .day -1 ). The maximum value of carotenoids content (0.3 mg.g DW -1 ) was achieved at the highest level of all factors. The total chlorophylls content reached also its maximum (5.18 mg.g DW -1 ) at high nitrate (1.76 mM), phosphate (0.054 mM), metals and vitamins concentrations, while the maximum starch content (42% DW) was achieved with low nitrate and phosphate concentrations (0.58 mM and 0.027 mM) and with metals and vitamins limitations. Thus, the nitrogen, phosphorus, metals and vitamins limitations led to divert the metabolism for the starch biosynthesis., Conclusions: The high biomass concentration productivity and starch production make Tetraselmis sp. strain a good candidate for biotechnological applications.

Microalgae have been used as natural ingredients to produce functional and nutritional food products. The impact of the addition of Chlorella minutissima, Isochrysis galbana, and Picochlorum sp. at concentrations of 0.5, 1, and 1.5% w/v on the texture and sensory attributes of canned burgers were investigated. The results show that carp formulations containing 1% microalgae show significantly better classification performance for many textural and sensory parameters compared to the rest of the formulations. Also, these treatments had higher swelling ability as well as water and oil holding capacities, thanks to the important dietary fiber and polysaccharide contents found in microalgae. Moreover, microalgae-supplemented burgers were characterized as having low a* and b* values, which made the color appear to be pale orange. Additionally, thanks to its richness in pigments and polysaccharides, microalgae considerably ameliorated the antioxidant activities of the new prepared fish burgers. Thus, microalgae could be used as natural and nutritious ingredient to develop new fish-based products. [ABSTRACT FROM AUTHOR]

The aim of this study is to predict Tetraselmis cells growth-kinetic and to induce the synthesis of bioactive compounds (chlorophylls, carotenoids and starch) with high potential for biotechnological applications. Using the statistical criteria, the Baranyi-Roberts model has been selected to estimate the microalgae growth-kinetic values. The simultaneous effects of salinity, light intensity and pH of culture medium were investigated to maximize the production of total chlorophylls, carotenoids and starch. The optimal culture conditions for the production of these compounds were found using Box-Behnken Design. Results have shown that total chlorophyll and carotenoids were attained 21.6 mg·g −1 DW and 0.042 mg·g −1 DW, respectively. In addition, the highest starch content of 0.624 g·g −1 DW has been obtained at neutral pH with high irradiance (182 μmol photons m −2  s −1 ) and low salinity (20). A highly correlation (R 2  = 0.884) has been found between the gravimetric and flow cytometric measurements of chlorophyll content. [ABSTRACT FROM AUTHOR]

Background: Three steps are very important in order to produce microalgal lipids: (1) controlling microalgae cultivation via experimental and modeling investigations, (2) optimizing culture conditions to maximize lipids production and to determine the fatty acid profile the most appropriate for biodiesel synthesis, and (3) optimizing the extraction of the lipids accumulated in the microalgal cells. Methods: Firstly, three kinetics models, namely logistic, logistic-with-lag and modified Gompertz, were tested to fit the experimental kinetics of the Chlorella sp. microalga culture established on standard conditions. Secondly, the response-surface methodology was used for two optimizations in this study. The first optimization was established for lipids production from Chlorella sp. culture under different culture conditions. In fact, different levels of nitrate concentrations, salinities and light intensities were applied to the culture medium in order to study their influences on lipids production and determine their fatty acid profile. The second optimization was concerned with the lipids extraction factors: ultrasonic's time and temperature, and chloroform-methanol solvent ratio. Results: All models (logistic, logistic-with-lag and modified Gompertz) applied for the experimental kinetics of Chlorella sp. show a very interesting fitting quality. The logistic model was chosen to describe the Chlorella sp. kinetics, since it yielded the most important statistical criteria: coefficient of determination of the order of 94.36%; adjusted coefficient of determination equal to 93.79% and root mean square error reaching 3.685 cells · ml− 1. Nitrate concentration and the two interactions involving the light intensity (Nitrate concentration × light intensity, and salinities × light intensity) showed a very significant influence on lipids production in the first optimization (p < 0.05). Yet, only the quadratic term of chloroform-methanol solvent ratio showed a significant influence on lipids extraction relative to the second step of optimization (p < 0.05). The two most abundant fatty acid methyl esters (≈72%) derived from the Chlorella sp. microalga cultured in the determined optimal conditions are: palmitic acid (C16:0) and oleic acid (C18:1) with the corresponding yields of 51.69% and 20.55% of total fatty acids, respectively. Conclusions: Only the nitrate deficiency and the high intensity of light can influence the microalgal lipids production. The corresponding fatty acid methyl esters composition is very suitable for biodiesel production. Lipids extraction is efficient only over long periods of time when using a solvent with a 2/1 chloroform/methanol ratio. [ABSTRACT FROM AUTHOR]

Due to the high consumption rate of fermented milk products such as yogurt, the fortification of these products will effectively reduce diseases associated with nutritional deficiencies. In the present study, after incorporating Spirulina into yogurt at four different concentrations (0.25, 0.5, 0.75 and 1%), we studied its effect on the fermentation process, texture, nutraceutical and sensory characteristics of yogurt. The addition of 0.25% of Spirulina was significantly sufficient to accelerate the end of fermentation (p < 0.05) and conserve the textural properties and sensory acceptability of the final milk product. This treatment also exhibited significant better water holding capacity and lower whey syneresis during 28 days of storage. During this period, the colored yogurt showed negligible variations for the L*, a* and b* indices, reflecting the strong stability of Spirulina color. Thanks to its high content in pigments, Spirulina considerably improve the antioxidant activity of the new formulated yogurt. Overall, it can be concluded that Spirulina can be used as a natural ingredient to develop a novel yogurt with high nutritional properties. [ABSTRACT FROM AUTHOR]