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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.
Metabolic Engineering for the Production of a Variety of Biofuels and Biochemicals
Published in Kazuyuki Shimizu, Metabolic Regulation and Metabolic Engineering for Biofuel and Biochemical Production, 2017
The fatty acid synthesis is made from AcCoA in the main metabolism, and produces fatty acyl-ACP (acyl carrier protein), which is directed cellular components such as structural and storage lipids. The fatty acid-derived chemicals are formed from thioesters (in fatty acid synthesis), fatty acyl-CoA thioesters (in fatty acid catabolism), or free fatty acids (from thioesterase) of cleavage of acyl-thioesters (Lennen and Pfleger 2013).
Biodiesel from oleaginous microbes: opportunities and challenges
Published in Biofuels, 2019
Lohit K. S. Gujjala, S. P. Jeevan Kumar, Bitasta Talukdar, Archana Dash, Sanjeev Kumar, Knawang Ch. Sherpa, Rintu Banerjee
In algae, generally C16–18 fatty acids are formed from the de novo fatty acid biosynthesis pathway. The fatty acids formed are then used for the production of neutral lipids such as TAG and the whole biosynthesis occurs within the chloroplast. For the biosynthesis of fatty acids, the committed step is the bioconversion of acetyl-CoA to malonyl-CoA. This carboxylation reaction takes place in two steps catalyzed by acetyl-CoA carboxylase (ACCase). The following sequence of steps takes place there onward: Initially, carbon dioxide is transferred to a nitrogen atom of biotin by the biotin carboxylase group of ACCase.This carbon dioxide is then transferred from biotin to acetyl-CoA, forming malonyl-CoA [81].Finally, the malonyl group is transferred from Coenzyme A to an acyl carrier protein (ACP), leading to a series of condensation reactions.The first step of the condensation reaction is catalyzed by 3-ketoacyl ACP synthase III (KAS III) [82] forming a four carbon product. Variation in the length of the carbon chain is catalyzed by KAS I. After each condensation reaction three additional reactions take place.This series of reactions is terminated upon the removal of the acyl group from ACP, which is catalyzed by thioesterase, thus leading to the release of fatty acids within the chloroplast.From the chloroplast, the free fatty acids are transferred to G3P, or monoacyl glycerol-3-phosphate [81] and then sequentially transferred to G3P, leading to the production of PA.Dephosphorylation of PA catalyzed by diacylglycerol acyltransferase produces diacylglycerol (DAG) which is subsequently added onto a fatty acid to produce TAG [83].