Abstract
Genetic engineering of microalgae to accumulate high levels of medium-chain-length fatty acids (MCFAs) represents an attractive strategy to improve the quality of microalgae-based biodiesel, but it has thus far been least successful. We demonstrate that one limitation is the availability of fatty acyl-acyl carrier protein (ACP) substrate pool for acyl-ACP thioesterase (TE). A combinational expression platform that involved plant lauric acid-biased TE (C12TE) and MCFA-specific ketoacyl-ACP synthase (KASIV) increased lauric acid (C12:0) and myristic acid (C14:0) accumulation by almost sevenfold and fourfold, respectively, compared with native strain. These findings suggest a platform for further investigation into the enlargement of MCFA acyl-ACP substrate pool as an approach to sustainably improve quality of microalgae-based biodiesel with regard to MCFA production.
Highlights
In response to the world energy crisis and the global climate change, microalgae-based biodiesel has attracted renewed interest in an effort to search for sustainable development (Zinoviev et al 2010)
Our results address whether endogenous TE and/or medium-chain-length fatty acid (FA) (MCFAs)-specific ketoacyl-ACP synthases (KASs) are involved in MCFA accumulation
The primary aim of this study was to investigate whether the availability of fatty acyl-acyl carrier protein (ACP) substrate pool for TE activity is one factor that limits the accumulation of MCFAs in transgenic D. tertiolecta strains
Summary
In response to the world energy crisis and the global climate change, microalgae-based biodiesel has attracted renewed interest in an effort to search for sustainable development (Zinoviev et al 2010). While most of the contemporary microalgae-based biodiesel research efforts focus on improving biomass accumulation and lipid productivity, relatively. Genetic engineering of FA profiles in microalgae to synthesize medium-chain-length FAs (MCFAs), from C8 to C14, is preferable for production of biodiesel (Durrett et al 2008). TEs are highly specific and are classified according to their substrate preferences, namely FatA and FatB. Certain plant species accumulate MCFAs in their seed oil storage, and there exist chain-length specific TEs that prematurely cleave the corresponding FAs from the growing fatty acyl-ACPs (Voelker and Kinney 2001). The first proof of principle of introducing chain-length specific TE to alter FA profile was demonstrated by Voelker and colleagues (1992) via engineering a lauric acid (C12:0)-biased FatB TE from U. californica into Arabidopsis thaliana for a 24% increase in C12:0 production
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