Supercritical carbon dioxide extraction of lipids from Pythium irregulare

Production Strategies and Applications of Microbial Single Cell Oils

Polyunsaturated fatty acids (PUFAs) of the ω-3 and ω-6 class (e.g., α-linolenic acid, linoleic acid) are essential for maintaining biofunctions in mammalians like humans. Due to the fact that humans cannot synthesize these essential fatty acids, they must be taken up from different food sources. Classical sources for these fatty acids are porcine liver and fish oil. However, microbial lipids or single cell oils, produced by oleaginous microorganisms such as algae, fungi and bacteria, are a promising source as well. These single cell oils can be used for many valuable chemicals with applications not only for nutrition but also for fuels and are therefore an ideal basis for a bio-based economy. A crucial point for the establishment of microbial lipids utilization is the cost-effective production and purification of fuels or products of higher value. The fermentative production can be realized by submerged (SmF) or solid state fermentation (SSF). The yield and the composition of the obtained microbial lipids depend on the type of fermentation and the particular conditions (e.g., medium, pH-value, temperature, aeration, nitrogen source). From an economical point of view, waste or by-product streams can be used as cheap and renewable carbon and nitrogen sources. In general, downstream processing costs are one of the major obstacles to be solved for full economic efficiency of microbial lipids. For the extraction of lipids from microbial biomass cell disruption is most important, because efficiency of cell disruption directly influences subsequent downstream operations and overall extraction efficiencies. A multitude of cell disruption and lipid extraction methods are available, conventional as well as newly emerging methods, which will be described and discussed in terms of large scale applicability, their potential in a modern biorefinery and their influence on product quality. Furthermore, an overview is given about applications of microbial lipids or derived fatty acids with emphasis on food applications.

Significant Enrichment of Polyunsaturated Fatty Acids (PUFAs) in the Lipids Extracted by Supercritical CO2 from the Livers of Australian Rock Lobsters (Jasus edwardsii)

Australian rock lobster (Jasus edwardsii) liver contains approximately 24.3% (w/w) lipids, which can contain a high amount of polyunsaturated fatty acids (PUFAs). However, this material has been found to be contaminated with arsenic (240 mg/kg) and cadmium (8 mg/kg). The high level of contaminants in the raw material and the large amount of PUFAs in the lipids prove a significant challenge in the extraction of high-quality lipids from this byproduct by conventional methods. Supercritical carbon dioxide (SC-CO2) extraction is a highly promising technology for lipid extraction with advantages including low contamination and low oxidation. The technique was optimized to achieve nearly 94% extraction of lipids relative to conventional Soxhlet extraction in Australian rock lobster liver at conditions of 35 MPa and 50 °C for 4 h. The extracted lipids are significantly enriched in PUFAs at 31.3% of total lipids, 4 times higher than those in the lipids recovered by Soxhlet extraction (7.8%). Specifically, the concentrations of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) in SC-CO2 extraction are 7 times higher than those obtained by Soxhlet extraction. Moreover, very small amounts of toxic heavy metals such as lead (Pb), arsenic (As), mercury (Hg), and cadmium (Cd) were detected in the SC-CO2-extracted lipids, 0.5-27 times lower than those in the Soxhlet-extracted lipids, which are 40-200 times lower than the regulatory limit maximum values. The low levels of contaminants and the high proportion of PUFAs (dominated by DHA and EPA) found in the SC-CO2-extracted lipids from Australian rock lobster liver suggest that the material could potentially be used as a valuable source of essential fatty acids for human consumption.

Supercritical fluid extraction of valuable compounds from microalgal biomass

Many studies have demonstrated that the global demand for renewable biofuels, natural food pigments, and antioxidants has made microalgae a more attractive alternative resource. The application of supercritical fluid extraction (SFE) on the valuable compounds recovery from microalgal biomass has several advantages as compared to the conventional organic solvent extraction methods, especially for environmental considerations. This review presents comprehensive information on the current state of using SFE to recover valuable components from microalgal biomass, such as total lipids, long chain fatty acid and pigments, as well as the utilization and characteristics of the SFE technology. In addition, key factors and challenges that should be addressed during the application of SFE technology are also discussed. This report provides a useful guide that can aid in the future development of more efficient microalgae-based biorefinery process.

Enhancement of lipid extraction from marine microalga, Scenedesmus associated with high-pressure homogenization process

Marine microalga, Scenedesmus sp., which is known to be suitable for biodiesel production because of its high lipid content, was subjected to the conventional Folch method of lipid extraction combined with high-pressure homogenization pretreatment process at 1200 psi and 35°C. Algal lipid yield was about 24.9% through this process, whereas only 19.8% lipid can be obtained by following a conventional lipid extraction procedure using the solvent, chloroform : methanol (2 : 1, v/v). Present approach requires 30 min process time and a moderate working temperature of 35°C as compared to the conventional extraction method which usually requires >5 hrs and 65°C temperature. It was found that this combined extraction process followed second-order reaction kinetics, which means most of the cellular lipids were extracted during initial periods of extraction, mostly within 30 min. In contrast, during the conventional extraction process, the cellular lipids were slowly and continuously extracted for >5 hrs by following first-order kinetics. Confocal and scanning electron microscopy revealed altered texture of algal biomass pretreated with high-pressure homogenization. These results clearly demonstrate that the Folch method coupled with high-pressure homogenization pretreatment can easily destruct the rigid cell walls of microalgae and release the intact lipids, with minimized extraction time and temperature, both of which are essential for maintaining good quality of the lipids for biodiesel production.

Enzyme-assisted extraction of lipids directly from the culture of the oleaginous yeast Rhodosporidium toruloides

Lipids produced by oleaginous microorganisms are a potential feedstock for biodiesel production and chemical synthesis. Yet, the costs of microbial lipids remain high, partially because the lipid recovery process is tedious and costly. In the present study, enzyme-assisted extraction of lipids from the culture of the yeast Rhodosporidium toruloides was carried out. With a heat pre-treatment with microwave, enzymatic treatment with the recombinant β-1,3-glucomannanase, plMAN5C, and extraction with ethyl acetate, 96.6% of the total lipids were extracted from R. toruloides cells at room temperature and atmospheric pressure directly from the culture without dewatering. Therefore, this process could significantly reduce energy consumption and costs for lipids extraction from the yeast.

Therapeutic drugs: healing power of marine fish

Marine fish is a major source of high-quality protein, lipids, and a wide variety of vitamins and minerals. These macromolecules and their derivatives show different pharmacological activities, which make the fish as a therapeutic diet. Modern technology has made it easy to explore the therapeutic importance of fish-based diet on cardiovascular diseases, neurodegenerative diseases, radicals-mediated diseases, and cancer. In this review, we focus on exploration of proteins, lipids, carbohydrates, minerals, and their derivatives from marine fish as a major source for bioactive compounds and their medicinal importance.

Combined extraction processes of lipid from Chlorella vulgaris microalgae: microwave prior to supercritical carbon dioxide extraction

Extraction yields and fatty acid profiles from freeze-dried Chlorella vulgaris by microwave pretreatment followed by supercritical carbon dioxide (MW-SCCO₂) extraction were compared with those obtained by supercritical carbon dioxide extraction alone (SCCO₂). Work performed with pressure range of 20–28 Mpa and temperature interval of 40–70 °C, gave the highest extraction yield (w/w dry weight) at 28 MPa/40 °C. MW-SCCO₂ allowed to obtain the highest extraction yield (4.73%) compared to SCCO₂ extraction alone (1.81%). Qualitative and quantitative analyses of microalgae oil showed that palmitic, oleic, linoleic and α-linolenic acid were the most abundant identified fatty acids. Oils obtained by MW-SCCO₂ extraction had the highest concentrations of fatty acids compared to SCCO₂ extraction without pretreatment. Native form, and microwave pretreated and untreated microalgae were observed by scanning electronic microscopy (SEM). SEM micrographs of pretreated microalgae present tearing wall agglomerates. After SCCO₂, microwave pretreated microalgae presented several micro cracks; while native form microalgae wall was slightly damaged.

Production and recovery of polyunsaturated fatty acids-added lipids from fermented canola

Canola flake was investigated as a potential substrate for fungal conversion to produce polyunsaturated fatty acids (PUFAs)-added oil in a 7l fermenter. The results showed that yields of total oil were reduced 9-22% compared to initial oil in the canola flake, but as high as 445mg/l arachidonic acid (ARA, C20:4n6) and 67mg/l eicosapentaenoic acid (EPA, C20:5n3) were produced. The percentages of ARA and EPA of total fatty acids in this fermented oil were 15.5% and 2.3%, respectively. Supercritical CO2 extraction was then investigated for the lipid recovery from fermented canola flake, and extraction kinetics were modeled. The feasibility was demonstrated for production of PUFAs in a laboratory-scale fermentor using canola flake as a single nutrient, and for lipid extraction using supercritical CO2.

Separation of biosynthetic polyunsaturated fatty acid (PUFA) with supercritical fluid

The separation of biosynthetic polyunsaturated fatty acid (PUFA) was undertaken with supercritical fluid. The polyunsaturated fatty acid was synthesised by WL-1021, which is a strain of marine bacterium isolated from marine fish. The polyunsaturated fatty acid can be very efficiently extracted from WL-1021 that has the characteristics of rapid growth in the artificial medium. The PUFA in WL-1021 has been successfully separated by supercritical fluid extraction (SFE). The SFE process parameters including pressure, temperature and culture temperature variations have been measured by High Performance Liquid Chromatography (HPLC), GC/FT-IR and GC/MS.

Supercritical Fluids and the Food Industry

This paper reviews the use of supercritical fluids in various aspects of the food industry, and is divided into six different areas: modeling of supercritical fluids, separation of extracted material, supercritical carbon dioxide as a solvent for extraction, supercritical fluids and analytical uses, and supercritical fluids and novel methods of food processing. An assortment of solutes are covered in the extraction section of the paper, including antineoplastic agents and lipids. The analytical methods section covers supercritical fluid chromatography, pesticide detection, and lipid analysis. The novel methods section discusses supercritical fluid extrusion and a new method of eliminating hexane from soybean oil.