A biorefinery from Nannochloropsis sp. microalga - energy and CO2 emission and economic analyses.

Are microalgae a potential energy source for biofuel production? This paper presents the laboratory results from a Nannochloropsis sp. microalga biorefinery for the production of oil, high-value pigments, and biohydrogen (bioH2). The energy consumption and CO2 emissions involved in the whole process (microalgae cultivation, harvest, dewater, mill, extraction and leftover biomass fermentation) were evaluated. An economic evaluation was also performed. Oil was obtained by soxhlet (SE) and supercritical fluid extraction (SFE). The bioH2 was produced by fermentation of the leftover biomass. The oil production pathway by SE shows the lowest value of energy consumption, 177-245 MJ/MJ(prod), and CO2 emissions, 13-15 kgCO(2)/MJ(prod). Despite consuming and emitting c.a. 20% more than the SE pathway, the oil obtained by SFE, proved to be more economically viable, with a cost of 365€/kg(oil) produced and simultaneously extracting high-value pigments. The bioH2 as co-product may be advantageous in terms of product yield or profit.

Herbicidal activity of volatiles from coriander, winter savory, cotton lavender, and thyme isolated by hydrodistillation and supercritical fluid extraction.

The volatiles from Coriandrum sativum L., Satureja montana L., Santolina chamaecyparissus L., and Thymus vulgaris L. were isolated by hydrodistillation (essential oil) and supercritical fluid extraction (volatile oil). Their effect on seed germination and root and shoot growth of the surviving seedlings of four crops ( Zea mays L., Triticum durum L., Pisum sativum L., and Lactuca sativa L.) and two weeds ( Portulaca oleracea L. and Vicia sativa L.) was investigated and compared with those of two synthetic herbicides, Agrocide and Prowl. The volatile oils of thyme and cotton lavender seemed to be promising alternatives to the synthetic herbicides because they were the least injurious to the crop species. The essential oil of winter savory, on the other hand, affected both crop and weeds and can be appropriate for uncultivated fields.

Composition and antioxidant activity of Thymus vulgaris volatiles: comparison between supercritical fluid extraction and hydrodistillation.

Supercritical fluid extraction (SFE) of the volatile oil from Thymus vulgaris L. aerial flowering parts was performed under different conditions of pressure, temperature, mean particle size and CO(2) flow rate and the correspondent yield and composition were compared with those of the essential oil isolated by hydrodistillation (HD). Both the oils were analyzed by GC and GC-MS and 52 components were identified. The main volatile components obtained were p-cymene (10.0-42.6% for SFE and 28.9-34.8% for HD), gamma-terpinene (0.8-6.9% for SFE and 5.1-7.0% for HD), linalool (2.3-5.3% for SFE and 2.8-3.1% for HD), thymol (19.5-40.8% for SFE and 35.4-41.6% for HD), and carvacrol (1.4-3.1% for SFE and 2.6-3.1% for HD). The main difference was found to be the relative percentage of thymoquinone (not found in the essential oil) and carvacryl methyl ether (1.0-1.2% for HD versus t-0.4 for SFE) which can explain the higher antioxidant activity, assessed by Rancimat test, of the SFE volatiles when compared with HD. Thymoquinone is considered a strong antioxidant compound.

Supercritical fluid extraction of the volatile oil from Santolina chamaecyparissus.

Supercritical fluid extraction (SFE) of the volatile oil from Santolina chamaecyparissus L. flower heads was performed under different conditions of pressure, temperature, mean particle size and CO(2) flow rate. This oil was compared with the essential oil isolated by hydrodistillation (HD). The SFE volatile and essential oils were analysed by GC and GC-MS. The range of the main volatile components obtained with HD and SFE were, respectively: 1,8-cineole (25-30% and 7-48%), camphor (7-9% and 8-14%), borneol (7-8% and 2-11%), terpinen-4-ol (6-7% and 1-4%), terpinolene (1-4% and 1-7%) and isobornyl acetate (1-2% and 1-11%). The chemical composition of the extracts was greatly influenced by the conditions of pressure and temperature used. In fact, it was possible to enrich the sesquiterpene fraction by increasing the pressure from 8 to 9 MPa, while changing the temperature from 50 to 40 degrees C at 9 MPa enriched the volatiles in n-alkanes [corrected].

Enrichment of the thymoquinone content in volatile oil from Satureja montana using supercritical fluid extraction.

Supercritical fluid extraction (SFE) of the volatile oil from Satureja montana L. was performed under different conditions of pressure (90 and 100 bar), temperature (40 and 50 degrees C), mean particle sizes (0.4, 0.6 and 0.8 mm) and CO(2) flow rate (0.8, 1.1 and 1.3 kg/h) to understand the influence of these parameters on the composition and yield of this oil. The results were compared with those obtained for the essential oil isolated by hydrodistillation (HD). The volatile and the essential oil were analysed by GC and GC-MS. The main compounds are carvacrol (52.2-62.0% for HD vs. 41.7-64.5% for SFE), thymol (8.6-11.0% for HD vs. 6.0-11.3% for SFE), p-cymene (6.9-12.8% for HD vs. 6.0-17.8% for SFE), gamma-terpinene (6.4-9.4% for HD vs. 2.3-6.0% for SFE) and beta-bisabolene (2.0-2.7% for HD vs. 2.2-3.5% for SFE). The major difference between SFE and HD was the relative amount of thymoquinone, an oxygenated monoterpene with important biological activities, which can be ten-fold higher in volatile oil (1.6-3.0 for SFE vs. 0.2% for HD). The morphology of the glandular trichomes of S. montana and the effect of the grinding process on them was also evaluated by SEM.