The 2008, 47 billion liters of biofuels

The growing worldwide demand of energy has brought with it increased depletion of fossil fuels and environmental issues derived from greenhouse gas emissions, local pollution, and global warming. This scenario makes it necessary to use alternative sources of energy based on the capture of carbon dioxide (CO2) through sustainable, renewable, and friendly processes. One promising alternative source of energy is the use of biofuels such as biodiesel (Mata et al. 2010; Fairley 2011; Atabani et al. 2012).Biodiesel is produced from oils extracted from edible crop plants such as rapeseed (Hill et al. 2006), soybean (Stephenson et al. 2008), and peanut (Nguyen et al. 2010), which in the context of worldwide hunger, has motivated controversies. As a consequence of such debate, biodiesel is being produced from oil extracted from non-food plants such as jatropha (Silitonga et al. 2011), Alexandrian laurel, and African oil plant (Sanjid et al. 2013). A second generation of biofuel production proposes enzymatically digesting plant’s woody parts for that same purpose (Sanderson 2011). Biodiesel production from oil-containing plants, either edible crops or not, is limited by several inconveniences such as long periods of production (months or years), lipid yields, dependence on climate, geographic location, soil fertility, the cultivar used, the extension needed for planting, and the massive volume of water needed for irrigation. For instance, in the UK during the year 2008, 47 billion liters of biofuels were used, of which 53% corresponded to biodiesel required for its production of 17.5 million hectares planted with rapeseed (Scott et al. 2010).Because of the abovementioned restrictions of biodiesel production, the industry requires alternative input allowing for a continuous operation and for overcoming such limitations. Technology based on eukaryotic microalgae and prokaryotic cyanobacteria has shown to be a promising source for biodiesel production (Rodolfi et al. 2009; Mata et al. 2010; Rajvanshi & Sharma 2012). In the UK, the production of biodiesel from cultures of Chlorella vulgaris has yields of 8200 t ha?1 y?1, three times higher than those of plantations of Jatropha curcas (2700 t ha?1 y?1) (Scott et al. 2010).Additionally, it was shown that the high cost of culturing algae, extracting their fatty acids and using them for biodiesel production, accounts for 40% of the current market of biodiesel (Agusdinata et al. 2011; Cremonez et al. 2015). While microalgae and cyanobacteria have shown to accumulate high percentages of lipids, their yields continue to be lower than expected (Mata et al. 2010; Rawat et al. 2013). At present, strategies including finding optimal culture conditions and genetic manipulation are being developed for improving the yields of lipids of microalgae. In the present paper, we briefly review the advances recently made in microalgae culture conditions and genetic manipulation for improving lipid yields, and present the results of in silico analysis of three enzymes involved in the biosynthesis of lipids in microalgae: acetyl-CoA carboxylase (ACC), Acyl-CoA: diacylglycerol acyltransferase (DGAT), and glycerol-3-phosphate acyltransferase (GPAT). Based on primary amino acid sequences and tertiary structure of proteins shared by certain algae groups, we show that it is likely that these proteins may also be related to fatty acid composition, yield, and accumulation. We state that habitat from which algae are isolated plays an important role in their fatty acid synthesis, so it is possible that the isolation of new strains of algae together with the selection and heterologous transformation of genes putatively involved in fatty acid biosynthesis could be an alternative for improving yield, accumulation, and composition of fatty acids in these microorganisms by genetic engineering.

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