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Algal Biofuel: A Promising Alternative for Fossil Fuel
Published in Maniruzzaman A. Aziz, Khairul Anuar Kassim, Wan Azelee Wan Abu Bakar, Aminaton Marto, Syed Anuar Faua’ad Syed Muhammad, Fossil Free Fuels, 2019
Hoofar Shokravi, Zahra Shokravi, Maniruzzaman A. Aziz, Hooman Shokravi
Lipid biosynthesis in microalgae mainly takes place through both fatty acid synthesis and TAG synthesis, which occur in the chloroplast and the endoplasmic reticulum, respectively. The fatty acid and TAG biosynthetic pathways have been fully characterized in microalgae. Fatty acid synthesis is performed by two different enzymatic systems including acetyl-CoA carboxylase (ACCase) and fatty acid synthase (FAS). The first step for the biosynthesis of fatty acid is synthesized under the catalysis of ACCase, which transforms acetyl-CoA to malonyl-CoA. The second step is catalyzed by FAS complex. The malonyl moiety is transferred to acyl carrier protein (ACP) and makes malonyl-ACP, which is added to another acyl-ACP to form an acyl chain with two carbons longer. Further reactions lead to a saturated and unsaturated acyl chain with acyl carrier protein. When the chain reaches the appropriate length, acyl carrier protein is removed from fatty acid, yielding the complete fatty acid. Furthermore, the synthesis of TAG is performed by four enzymes, including glycerol-3- phosphate dehydrogenase (GPDH), lysophosphatidic acyltransferase (LPAAT), diacylglycerol acyltransferase (DGAT) and glycerol-3-phosphate acyltransferase (GPAT). Therefore, the overexpression of these genes has been used as a technique to promote lipid content [58–60].
Tailoring Triacylglycerol Biosynthetic Pathway in Plants for Biofuel Production
Published in Arindam Kuila, Sustainable Biofuel and Biomass, 2019
Kshitija Sinha, Ranjeet Kaur, Rupam Kumar Bhunia
The four most important oilseed crops are soybean, oil palm, rapeseed, and sunflower which contain four fatty acids, that is, linoleic acid (18:2 cis-9,12), palmitic acid (16:0), lauric acid (12:0), and oleic acid (18:1), abundantly in their seeds. However, there are five major fatty acids in plants which constitute 90% of the acyl chains of the glycerolipids of almost all membranes found in plants. These fatty acids have 16 or 18 carbons in the chains (i.e., 18:1, 18:2, 18:3, 16:0, and in some species, 16:3), and they contain one to three cis double bonds (Thelen and Ohlrogge, 2001). The de novo biosynthesis of fatty acid is catalyzed by acetyl-CoA carboxylase and the fatty acid synthase known as Kennedy Pathway (Bates, et al., 2013). The unsaturated fatty acids of 4–18 carbons are synthesized in plastid and the fatty acyl chain then is attached to the acyl carrier protein of the fatty acid synthase complex. The fatty acyl chain is released from the carrier protein by thioesterase. Once exported from the plastid, acyl-Coenzyme A (acyl-CoA) synthetase combines fatty acid chains to CoA-forming acyl-CoA on the outer membrane of plastids.
Biofuel and Biochemical Production by Photosynthetic Organisms
Published in Kazuyuki Shimizu, Metabolic Regulation and Metabolic Engineering for Biofuel and Biochemical Production, 2017
As shown in Fig. 10a, AcCoA is converted to malonyl-CoA by a multisubunit AcCoA carboxylase consisting of AccA, AccB, AccC and AccD encoded by accBCDA, the rate-limiting step of the fatty acid synthesis (Davis et al. 2000). Fatty acid substrates as acyl chains of membrane lipids are synthesized by fatty acid synthase (FAS). Acyl-ACPs (acyl-acyl carrier proteins) synthesized by FAS can be incorporated to membrane lipids. Free fatty acids (FFAs) generated by lypolytic enzymes during degradation of membrane lipids can be also activated to acyl-ACPs by acyl-ACO synthetase (AAS, EC 6.2.1.20) (Kaczmarzky and Fulda 2010). The only AAS gene in Synechocystis sp. PCC 6803 is slr1609 (Kaczmarzky and Fulda 2010). Therefore, slr1609-knockout mutant is incapable of importing exogeneous fatty acids and secreted fatty acids released from membrane lipids into the culture broth, which indicates the remarkable role of AAS in recycling the released fatty acids (Kaczmarzky and Fulda 2010). AAS also plays an essential role in alka(e)ne production, because slr1609 deletion mutant of Synechocystis sp. PCC6803 showed significantly low production of alka(e) nes (Gao et al., 2012).
Determination of the natural deuterium distribution of fatty acids by application of 2H 2D-NMR in liquid crystals: fundamentals, advances, around and beyond
Published in Liquid Crystals, 2020
From acetyl-coA, FAs are biosynthesised by the enzyme ‘fatty acid synthase’ (FAS) by a replication mechanism, then modified under the action of different enzymes (Conjugase, Desaturase, Epoxydase). To simply illustrate the purpose, Figure 5 presents the successive transformations of methyl stearate (MS), a C-18 saturated AG into methyl oleate (MO, 9Z-18:1), methyl linoleate (ML, 9Z, 10Z-18:2), and then in a second step of enzymatic reactions into methyl linolate (LnM, 9Z, 12Z, 15Z,-18:3), methyl α-eleostearate (ME, 9Z, 11E, 13E,-18:3) or methyl punicate (MPu, 9Z, 11E, 13Z,-18:3)) and methyl vernoleate (MV, 9Z, 12R, 13S,-18:1), from the ML. Among PUFAs investigated, only MVpossess stereogenic centres (sites 12 and 13) which the stereochemistry is known (12R,13S). MV is mainly used in paint industry. Finally, the 1,1′-bis(phenylthio)hexane (BPTH) is a fragment of ML obtained by chemical cleavage (see below). ML and MLn are termed as essential FAs.