Abstract
BackgroundBiofuel has been the focus of intensive global research over the past few years. The development of 4th generation biofuel production (algae-to-biofuels) based on metabolic engineering of algae is still in its infancy, one of the main barriers is our lacking of understanding of microalgal growth, metabolism and biofuel production. Although fatty acid (FA) biosynthesis pathway genes have been all cloned and biosynthesis pathway was built up in some higher plants, the molecular mechanism for its regulation in microalgae is far away from elucidation.ResultsWe cloned main key genes for FA biosynthesis in Haematococcus pluvialis, a green microalga as a potential biodiesel feedstock, and investigated the correlations between their expression alternation and FA composition and content detected by GC-MS under different stress treatments, such as nitrogen depletion, salinity, high or low temperature. Our results showed that high temperature, high salinity, and nitrogen depletion treatments played significant roles in promoting microalgal FA synthesis, while FA qualities were not changed much. Correlation analysis showed that acyl carrier protein (ACP), 3-ketoacyl-ACP-synthase (KAS), and acyl-ACP thioesterase (FATA) gene expression had significant correlations with monounsaturated FA (MUFA) synthesis and polyunsaturated FA (PUFA) synthesis.ConclusionsWe proposed that ACP, KAS, and FATA in H. pluvialis may play an important role in FA synthesis and may be rate limiting genes, which probably could be modified for the further study of metabolic engineering to improve microalgal biofuel quality and production.
Highlights
Biofuel has been the focus of intensive global research over the past few years
The results showed that the mRNA levels of most selected genes were significantly or very significantly upregulated under all stress conditions, with all genes were up-regulated under Fe + AC and high temperature (HT) conditions, and some genes, such as Acyl-ACP thioesterase (FATA), SAD and fatty acid desaturase (FAD), were more sensitive to treatments (Figure 2)
Under LT, biotin carboxylase (BC) mRNA level was increased up to 4.8 fold, which was far lower than that of HT (1,626), indicating that fatty acid (FA) biosynthesis in H. pluvialis is more sensitive to high temperature than low temperature
Summary
Biofuel has been the focus of intensive global research over the past few years. The development of 4th generation biofuel production (algae-to-biofuels) based on metabolic engineering of algae is still in its infancy, one of the main barriers is our lacking of understanding of microalgal growth, metabolism and biofuel production. Environmentally friendly, safe to use, with wide applications, as well as biodegradable, it has become a major focus on intensive global research and development of new energy. The importance of screening high FA content microalgae species and optimization for large biomass culture conditions were recognized as early as in 1980s [9]. Research in this area mainly focused on comparing FA composition in different microalgae and a variety of stress on content and composition of the FA in microalgae [10,11,12]. One of the main barriers is the high producing cost due to our lacking of understanding of microalgal growth, metabolism and biofuels production
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