Advancing oleaginous microorganisms to produce lipid via metabolic engineering technology

Abstract

With the depletion of global petroleum and its increasing price, biodiesel has been becoming one of the most promising biofuels for global fuels market. Researchers exploit oleaginous microorganisms for biodiesel production due to their short life cycle, less labor required, less affection by venue, and easier to scale up. Many oleaginous microorganisms can accumulate lipids, especially triacylglycerols (TAGs), which are the main materials for biodiesel production. This review is covering the related researches on different oleaginous microorganisms, such as yeast, mold, bacteria and microalgae, which might become the potential oil feedstocks for biodiesel production in the future, showing that biodiesel from oleaginous microorganisms has a great prospect in the development of biomass energy. Microbial oils biosynthesis process includes fatty acid synthesis approach and TAG synthesis approach. In addition, the strategies to increase lipids accumulation via metabolic engineering technology, involving the enhancement of fatty acid synthesis approach, the enhancement of TAG synthesis approach, the regulation of related TAG biosynthesis bypass approaches, the blocking of competing pathways and the multi-gene approach, are discussed in detail. It is suggested that DGAT and ME are the most promising targets for gene transformation, and reducing PEPC activity is observed to be beneficial for lipid production.

Keywords: ACC; ACL; ACP; ADP-glucose pyrophosphate; AGPase; AOX; ARA; ATP:citrate lyase; BE; Biodiesel; CDP-DAG; CDP-diacylglycerol; DAG; DGAT; DHA; DHAP; DHAP acyltransferase; DHAPAT; EPA; FAS; FAT; FFA; G-1-P; G-6-P; G3P; GAP; GLA; GPAT; GPD1 and GUT2; KAS; LPA; LPAT; Lipids; MAT; ME; Metabolic engineering; Microalgae; Microbial oils; Oleaginous microorganisms; PA; PAP; PDAT; PDH; PEP; PEPC; PYC; Pi; SS; TAG; WS/DGAT; acetyl-CoA carboxylase; acyl-ACP-thioesterase; acyl-CoA oxidase; acyl-carrier protein; arachidonic acid; branching enzymes; diacylglycerol; diacylglycerol acyl-transferase; dihydroxyacetone phosphate; docosahexenoic acid; eicosapentaenoic acid; fatty acid synthetase; free fatty acid; gamma-linolenic acid; glucose 1-phosphate; glucose 6-phosphate; glyceraldehyde 3-phosphate; glycerol 3-phosphate dehydrogenase; glycerol-3-phosphate; glycerol-3-phosphate acyltransferase; inorganic pyrophosphate; lysophosphatidate; lysophosphatidate acyl-transferase; malic enzyme; malonyl-CoA:ACP transacetylase; phosphatidate; phosphatidic acid phosphatase; phosphoenolpyruvate; phosphoenolpyruvate carboxylase; phospholipid:diacylglycerol acyltransferase; pyruvate carboxylase; pyruvate dehydrogenase; starch synthase; triacylglycerol; wax ester synthase/acyl-CoA:diacylglycerol acyltransferase; β-ketoacyl-ACP synthase.