China
Africa
Explore chapters and articles related to this topic
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 initiation of synthesis of all glycerolipids includes acylation of sn-glycerol-3-phosphate (G-3-P) to lysophosphatidic acid which is catalyzed by sn-1 glycerol-3-phosphate acyltransferase (GPAT). The frequent participation of acyl-CoA in comparison to any other substrate in this step leads to an asymmetric distribution of saturated and unsaturated fatty acids in different positions of phospholipids and TAGs. Further elongation of the acyl chains occurs in ER (Fig. 3.1). The role of GPAT in glycerolipid synthesis is still a topic of discussion as it is seen that the in yeast, one of the isoforms, SCT1, when overexpressed, enhances TAG accumulation while the other isoform, GPT1 decreases the accumulation. The homologs of GPAT in plants such as Arabidopsis have also been studied. It is seen that mutation in these genes does not affect the oil metabolism. However, it has been known that GPAT4 and GPAT6 participate in other functions such as generation of monoacylglycerol which ultimately leads to the cutin biosynthesis (Zheng et al., 2003). The next step is catalyzed by an enzyme called lysophosphatidic acid acyltransferase enzyme (LPAAT) which converts lysophosphatidic acid to phosphatidic acid. It is believed that LPAAT favors different types of fatty acyl-CoAs in different type of plants. LPAAT enzyme in Tropaeolaceae and Limnanthaceae family prefer very long fatty acyl-CoAs; similarly, medium-length fatty acyl-CoAs are preferred by this enzyme in plants such as coconut and palm. The third step in this pathway is the formation of diacylglycerol (DAG) from phosphatidic acid (Maisonneuve et al., 2010). The enzyme involved here is known as phosphatidate phosphatase1 (PAP1), which dephosphorylates phosphatidic acid. The final step in the biosynthesis of TAG is catalyzed by an enzyme called diacylglycerol acyltransferase (DGAT) which converts DAG to TAG (Weselake et al., AOCS lipid library).
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
Besides diatoms, some green microalgae have also been explored for metabolic engineering experiments. When acyl-CoA: diacylglycerol acyltransferases (DGAT) of endogenous origin (CrDGAT2a, CrDGAT2b and CrDGAT2c) regulating glycerol acylation were overexpressed in Chlamydomonas reinhardtii, no change in TAG yield and composition was observed [112]. Deng et al. [113] reported an increase of total lipid up to 34% after the RNAi silencing of CrDGAT2-4 only. This contradicts the report of La Russa et al. [113], who observed an increase of neutral lipids (35%) by the overexpression of DGAT2 (endogenous) in P. tricornutum. Similarly, a 2-fold rise in TAGs was observed in Chlorella minutissima by expressing five different enzymes from yeast (source: Saccharomyces cerevisiae and Yarrowia lipolytica). The enzymes include DGAT, phosphatidic acid phosphatase (PAP), glycerol-3-phosphate acyltransferase (GPAT), lysophosphatidic acid acyltransferase (LPAAT) and glycerol-3-phosphate dehydrogenase (G3PDH) [114]. An overview of the target genes which can be overexpressed for enhancing lipid content in fungal and algal systems is shown in Figures 3 and 4 [115,116], respectively, and a tabulation of some recent experimental attempts to improve lipid contents in microbial sources using metabolic engineering techniques is given in Table 2.
Non-stomatal limitation of photosynthesis by soil salinity
Published in Critical Reviews in Environmental Science and Technology, 2021
Ting Pan, Minmin Liu, Vladimir D. Kreslavski, Sergey K. Zharmukhamedov, Chenrong Nie, Min Yu, Vladimir V. Kuznetsov, Suleyman I. Allakhverdiev, Sergey Shabala
Zhang et al. (2009) studied a role of unsaturation of fatty acids in salt tolerance in Arabidopsis seedlings and found that fatty acid desaturase-6 (Fad6) was required. fad6 mutants of Arabidopsis seedlings that lacked chloroplast fatty acid desaturase showed lowered resistance to salt stress compared to WT plants. Also, overexpression of SsGPAT (glycerol-3-phosphate acyltransferase; a key enzyme in synthesis of phosphatidylglycerol, the only phospholipid located in photosynthetic membranes (Wada & Murata, 1998) in Arabidopsis enhanced salt tolerance and reduced PSII and PSI photoinhibition under salt stress by adjustment of PG the unsaturated fatty acid content in Arabidopsis (Sui, Tian, Wang, Wang, & Fan, 2017).
Design of artificial cells: artificial biochemical systems, their thermodynamics and kinetics properties
Published in Egyptian Journal of Basic and Applied Sciences, 2022
Adamu Yunusa Ugya, Lin Pohan, Qifeng Wang, Kamel Meguellati
A bottom-up approach is to build a stack of non-biotic components which are assembled to create de novo an artificial cell with a phospholipid bilayer and self-replicating DNA via a genetic program [18]. Typically, the approach involves three basic elements, which include information-carrying molecules (DNA or RNA), metabolic systems, and cell membranes. Two membrane proteins, sn-glycerol-3-phosphate acyltransferase (GPAT) and lyo-phosphatidic acid transferase (LPAAT), are produced by protein synthesis using recombinant element systems (PURE) enclosed in liposomes [23].