Abstract
BackgroundMicroalgae biofuel has become the most promising renewable energy over the past few years. But limitations still exist because of its high cost. Although, efforts have been made in enhancement of lipid productivity, the major cost problem in harvesting and oil extraction is still intractable. Thus, the idea of fatty acids (FAs) secretion which can massively facilitate algae harvesting and oil extraction was investigated here.ResultsThe cDNAs of two long-chain acyl-CoA synthetases (LACSs) genes were cloned from Chlamydomonas reinhardtii and named as cracs1 and cracs2. They showed different substrate adaptation in the yeast complementation experiments. Cracs2 could utilize FAs C12:0, C14:0, C16:0, C18:0, C16:1 and C18:1, while crac1 could only utilize substrate C14:0, C16:1 and C18:1. Knockdown of cracs1 and cracs2 in C. reinhardtii resulted in accumulation of intracellular lipids. The total intracellular lipids contents of transgenic algae q-15 (knockdown of cracs1) and p-13 (knockdown of cracs2) were 45 and 55 %, respectively higher than that of cc849. Furthermore, FAs secretion was discovered in both transgenic algae. Secreted FAs can reach 8.19 and 9.66 mg/109 cells in q-15 and p-13, respectively.ConclusionThese results demonstrated the possibility of FAs secretion by microalgae and may give a new strategy of low-cost oil extraction. According to our findings, we proposed that FAs secretion may also be achieved in other species besides Chlamydomonas reinhardtii by knocking-down cracs genes, which may promote the future industrial application of microalgae biofuels.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0598-7) contains supplementary material, which is available to authorized users.
Highlights
Microalgae biofuel has become the most promising renewable energy over the past few years
These results demonstrated the possibility of fatty acids (FAs) secretion by microalgae and may give a new strategy of low-cost oil extraction
We proposed that FAs secretion may be achieved in other species besides Chlamydomonas reinhardtii by knocking-down cracs genes, which may promote the future industrial application of microalgae biofuels
Summary
Microalgae biofuel has become the most promising renewable energy over the past few years. Efforts have been made in enhancement of lipid productivity, the major cost problem in harvesting and oil extraction is still intractable. The idea of fatty acids (FAs) secretion which can massively facilitate algae harvesting and oil extraction was investigated here. Biofuel has been widely studied over the past few years and is considered to be the most promising renewable energy to ease global energy crisis. Due to the limited amount of raw materials, the production of traditional biofuel from crops was dramatically constrained. Acyl-CoA synthetases (ACSs) can activate fatty acids (FAs) into CoA thioesters which can serve as the substrate for many metabolic pathways, such as fatty acids elongation and desaturation, lipid synthesis, and β-oxidation [7]. Arabidopsis thaliana contains at least nine LACSs, of which AtLAC6 and AtLAC7 locate in peroxisome responsible for FAs β-oxidation [10]
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