ABSTRACT
Today microalgae represent a viable alternative source for high-value products. The specie Chlorella protothecoides (Cp), heterotrophically grown, has been widely studied and provides a high amount of lutein and fatty acids (FA) and has a good profile for biodiesel production. This work studies carotenoid and FA production by autotrophic grown Cp. Cp was grown until the medium's nitrogen was depleted, then diluted in NaCl solution, resulting in nutritional, luminosity, and salinity stresses. Different NaCl concentrations were tested (10, 20, 30 g/L) at two different dilutions. After dilution, a color shifting from green to orange-red was noticed, showing carotenoid production. The best production of both carotenoids and FA was attained with a 20 g/L NaCl solution. The total carotenoid content was 0.8 % w/w (canthaxanthin (23.3 %), echinenone (14.7 %), free astaxanthin (7.1 %), and lutein/zeaxanthin (4.1 %)). Furthermore, the total lipid content reached 43.4 % w/w, with a FA composition of C18:1 (33.64 %), C16:0 (23.30 %), C18:2 (11.53 %), and less than 12 % of C18:3, which is needed to fulfill the biodiesel quality specifications (EN 14214).
Subject(s)
Carotenoids/metabolism , Chlorella/metabolism , Light , Lipid Metabolism , Salinity , Stress, Physiological , Biofuels , Chlorella/drug effects , Chlorella/physiology , Chlorella/radiation effects , Color , Fermentation , Sodium Chloride/metabolismABSTRACT
The antioxidant activities of the volatile and the nonvolatile fractions from Satureja montana obtained by supercritical fluid extraction (SFE) and by conventional techniques, hydrodistillation (HD) and soxhlet extraction (SE), were compared. A good agreement between DPPH and rancimat methods was obtained showing that the extracts were able to scavenge free radicals and to inhibit lipid oxidation. The volatile oil (obtained by SFE at 90 bar/40 degrees C) was the most effective extract, presenting the lowest EC(50) (0.06 g/L) and the highest protector factor (PF = 2.03). These results demonstrated the advantages of SFE over conventional techniques by avoiding thermodegradation and hydrolysis reactions. Furthermore, volatile oil is 15 times richer in thymoquinone than the essential oil (HD). This compound is of great importance due to its antioxidant, neuroprotective, and anti-cancer activities. The combination of carvacrol + thymol + thymoquinone in volatile oil may be responsible for the increase in the antioxidant activity when compared to HD, which demonstrates that, in this case, SFE improves value to the final product.
Subject(s)
Antioxidants/chemistry , Chemical Fractionation/methods , Plant Extracts/chemistry , Plant Extracts/isolation & purification , Satureja/chemistry , Antioxidants/analysis , Antioxidants/isolation & purification , Benzoquinones/analysis , Cymenes , Fatty Acids/analysis , Fatty Acids, Nonesterified/analysis , Food Preservatives/chemistry , Food Preservatives/isolation & purification , Monoterpenes/analysis , Oils, Volatile/chemistry , Oils, Volatile/isolation & purification , Oxidation-Reduction , Plant Components, Aerial/chemistry , Plant Oils/chemistry , Sunflower Oil , Temperature , Thymol/analysis , Time Factors , Volatile Organic Compounds/analysisABSTRACT
An apparatus is described which can be used for PVT and compressibility measurements on supercritical fluids from near room temperature to 600 °C and pressures to 35 MPa. Two separate experimental techniques are employed to obtain PVT data over a broad range of the state surface. Burnett expansions are performed to generate compressibility factor (or equivalently density) data along a well-behaved supercritical isotherm. A series of isochoric measurements is then made to extend the temperature range. Densities assigned to the isochores are determined from their intersection with the previously measured Burnett isotherm or gravimetrically. A computer is used for experimental control and for data logging. Isochoric measurements lasting several days can be performed routinely and without operator attention. The apparatus has been tested on propane to a temperature of 325 °C. The density data, estimated accurate to ±0.1 percent, are in excellent agreement with other existing data.
