Maximizing carotenoid extraction from microalgae used as food additives and determined by liquid chromatography (HPLC)

Effect of a Shading Mesh on the Metabolic, Nutritional, and Defense Profiles of Harvested Greenhouse-Grown Organic Tomato Fruits and Leaves Revealed by NMR Metabolomics

Controlling the temperature inside a greenhouse during the summer is a problem of increasing importance in the Mediterranean countries, especially in the Spanish southeast. The metabolic profile of greenhouse tomatoes and leaves grown under conventional conditions and within the presence of a shade mesh (∼50% reduction of sunlight radiation) has been monitored. Tomatoes were weekly harvested from May to July 2017 and analyzed by NMR spectroscopy coupled to multivariate data analysis techniques, together with oxygen radical absorbance capacity (ORAC) assays (for antioxidant activity). Fatty acids and carotenoids profiles were unraveled by GC-FID and HPLC-DAD, respectively. To verify whether it would be possible to take advantage of different light growing conditions to potentiate a plant's defense system, leaves of the corresponding plants were collected and their methanolic extracts were analyzed by NMR toward deciphering new biomarkers, which were used to assess their antibacterial and antibiofilm activities. The presence of a shading mesh resulted in a reduction in tomato production and in smaller fruits with lower contents of sugars (glucose and fructose) and carotenoids (lycopene and β-carotene) and higher contents of organic acids, amino acids, and polyunsaturated fatty acids (linoleic and oleic acids) and of phenylpropanoids and flavonoids (which contributed to an increased antioxidant activity). Methanolic extracts of leaves of nonshaded plants showed a higher antibiofilm activity than that from shaded plants. This activity was well-correlated with an increase of phenolic compounds, together with some specific amino acids and organic acids from tomato leaves.

Bioprospection of Isochrysis galbana and its potential as a nutraceutical

Microalgae have strong potential as novel sources of nutraceuticals, as they contain significant amounts of highly valuable bioactive compounds. This study focuses on the bioprospection of biomass of the microalga Isochrysis galbana and its extracts (aqueous and ethanolic), determining total polyphenols, laminarin, fucoxanthin, coenzyme Q10, and β-carotene contents, and also assessing several biological activities (antioxidant, cytotoxicity, and hypocholesterolemic). I. galbana exhibited high phenolic content, both in aqueous and ethanolic extracts. The microalgal freeze-dried biomass presented a low laminarin content and higher content of fucoxanthin (6.10 mg per g dw), and relevant β-carotene and Coenzyme Q10 contents were detected. I. galbana aqueous extracts presented a high antioxidant capacity (approximately 90% inhibition by the ABTS method). Furthermore, I. galbana biomass and ethanolic extract showed significant cytotoxicity against HeLa human cervical cancer cells, with IC₅₀ values of 0.32 and 0.28 mg ml^-1 respectively, demonstrating potential for further anticancer studies. The aqueous extract of I. galbana induced a significant decrease of cholesterol absorption through Caco-2 monolayers, modelling the human intestinal barrier, which suggests that it may contribute to decreasing the dietary cholesterol absorption.

Effect of batch and continuous thermosonication on the microbial and physicochemical quality of pumpkin juice

The study investigated the use of batch and continuous thermosonication for pasteurization of pumpkin (Cucurbita moschata) juice emphasizing on its microbial, physicochemical and sensorial quality parameters. Batch thermosonication (40, 50, 60 °C, 37 kHz, 150 W) of pumpkin juice was compared with the ultrasonication (23 °C) and conventional heat treatments (40, 50, 60 °C). For batch thermosonication, maximum inactivation of Escherichia coli K-12 was 6.62 ± 0.00 log cfu/mL, meanwhile, it was 3.64 ± 0.19 log cfu/mL for heat treatment. In addition, only 0.37 ± 0.21 log cfu/mL inactivation in E. coli K-12 was obtained by ultrasonication. The designed continuous thermosonication system (0.029 L/min, 60 °C) reduced E. coli K-12 by 6.23 ± 0.34 cfu/mL log after cycle 3 (34.15 min of processing). Color properties (L*, a*, b*, ∆E), pH, total titratable acidity, total soluble solids content, turbidity and non-enzymatic browning index were determined for batch and continuously thermosonicated, ultrasonicated and heat-treated pumpkin juices. Total color change of continuously thermosonicated samples were higher than the batch thermosonicated (60 °C) ones but, lower than the conventional heat treated (60 °C) samples. Sensory panel showed general acceptance scores of fresh, batch (60 °C) and continuously thermosonicated pumpkin juice samples have no significant (P < 0.05) difference. Continuous treatment results supported by the batch ones revealed that thermosonication could be effectively used for pasteurization of pumpkin juice producing a safe product with minimum changes in physicochemical and sensorial properties.

First Apocarotenoids Profiling of Four Microalgae Strains

Both enzymatic or oxidative carotenoids cleavages can often occur in nature and produce a wide range of bioactive apocarotenoids. Considering that no detailed information is available in the literature regarding the occurrence of apocarotenoids in microalgae species, the aim of this study was to study the extraction and characterization of apocarotenoids in four different microalgae strains: Chlamydomonas sp. CCMP 2294, Tetraselmis chuii SAG 8-6, Nannochloropsis gaditana CCMP 526, and Chlorella sorokiniana NIVA-CHL 176. This was done for the first time using an online method coupling supercritical fluid extraction and supercritical fluid chromatography tandem mass spectrometry. A total of 29 different apocarotenoids, including various apocarotenoid fatty acid esters, were detected: apo-12’-zeaxanthinal, β-apo-12’-carotenal, apo-12-luteinal, and apo-12’-violaxanthal. These were detected in all the investigated strains together with the two apocarotenoid esters, apo-10’-zeaxanthinal-C4:0 and apo-8’-zeaxanthinal-C8:0. The overall extraction and detection time for the apocarotenoids was less than 10 min, including apocarotenoids esters, with an overall analysis time of less than 20 min. Moreover, preliminary quantitative data showed that the β-apo-8’-carotenal content was around 0.8% and 2.4% of the parent carotenoid, in the C. sorokiniana and T. chuii strains, respectively. This methodology could be applied as a selective and efficient method for the apocarotenoids detection.

Assessment of multi-step processes for an integral use of the biomass of the marine microalga Amphidinium carterae

Sustainable dinoflagellate microalgae-based bioprocess designed to produce secondary metabolites (SMs) with interesting bioactivities are attracting increasing attention. However, dinoflagellates also produce other valuable bioproducts (e.g polyunsaturated fatty acids, carotenoids, etc.) that could be recovered and should therefore be taken into account in the bioprocess. In this study, biomass of the marine dinoflagellate microalga Amphidinium carterae was used to assess and optimise three different methods in order to obtain three families of high-value biochemical compounds present in the biomass. The existing processes encompassed a multi-step extraction process for carotenoids, fatty acids and APDs individually and are optimized for the integral valorization of raw A. carterae biomass, with SMs being the primary target compounds. Total process recovery yields were 97% for carotenoids, 80% for total fatty acids and 100% for an extract rich in APDs (not purified).

NMR Metabolomics as an Effective Tool To Unravel the Effect of Light Intensity and Temperature on the Composition of the Marine Microalgae Isochrysis galbana

NMR spectroscopy coupled with multivariate data analysis techniques was applied to obtain meaningful information about nontargeted metabolic changes on  Isochrysis galbana upon acclimation to different environmental conditions at indoor lab-scale. The effects of temperature (from 15 to 30 °C) and incident irradiance (from 250 to 1600 μmol m^-2 s^-1) at a constant dilution rate of 0.3 h^-1 were evaluated. High irradiances stimulated a decrease of chlorophyll a, fucoxanthin and amino acids content, and the conversion of polar fatty acids (PLs, GLs, DGDGs, SGDGs) to neutral fatty acids (saturated and unsaturated). High temperatures together with high irradiances decreased PUFAs concentration, including omega-3 fatty acids. Under low irradiance and temperature organic osmolytes (homarine, DMSP, GBT, and glycerol), and sugars (glucose, trehalose, and galactose) were also reduced.

Strengthening mass transfer of carbon dioxide microbubbles dissolver in a horizontal tubular photo-bioreactor for improving microalgae growth

A CO₂ microbubbles dissolver (CMD) was developed to facilitate dissolving inorganic carbon and strengthening mass transfer in a horizontal tubular photo-bioreactor system (HTPBRS), which enhanced microalgae biomass productivity with flue gas containing 15% CO₂. The influence of pump power on the bubble formation and mixing effect was found to be more obvious than that of gas flow rate. Ceramic shell aerator was more favorable for reducing bubble diameter and enhancing mass transfer than traditional rubber strip aerator. Bubble formation time decreased by 53.4% and mixing time decreased by 68.9% in response to the increased pump power. When the base area ratio of ceramic shell aerator to dissolver in the HTPBRS increased, bubble formation time decreased by 19.6% and mass transfer coefficient increased by 80.9%. The biomass yield of microalgae Chlorella PY-ZU1 with ceramic shell aerator was 30% higher than that with rubber strip aerator in the HTPBRS.