Abstract
The cyanobacteria have great potential for aquaculture industries, bioproducts, bioenergy and bioremediation, as in the reduction of ammonia, phosphorus and organic compounds. The manipulation of the medium and the modes of operation of the cultures are necessary to induce the production of biomass and bioproducts, such as lipids. The aim of the study was to evaluate the different nitrogen sources and their depletion in heterotrophic cultures of the cyanobacterium Phormidium autumnale aimed at obtaining high yields lipid. The heterotrophic cultures were carried out in bubble column bioreactor employing cassava starch as organic carbon source. In the first stage, were studied different nitrogen source under the C/N (carbon/nitrogen) ratios in the culture medium of 20, 40 and 60. In the second stage, selected to nitrogen source with the greatest potential for the production of lipids and held its depletion searching for the induction of a cellular stress. The fatty acids profile in the end of cultures was used in the estimation of biodiesel quality. In the first stage, the cultures employing sodium nitrate under CN ratio of 60 resulting in lipid content of 13.22% and lipid productivity of 7.62 mg/L.h. From the depletion of sodium nitrate, second stage, obtained a lipid productivity and lipid content of 10.43 mg/L.h and 25.07%, respectively. The fatty acid profile showed, in the presence of nitrogen, saturated fatty acid fraction and monounsaturated of 76.72% and 23.88%, respectively. The depletion of sodium nitrate induced a change in the lipid profile, directing the concentration of saturated fatty acids of 98.97%. The biodiesel properties obtained meet the standards set by standardization of the quality of biodiesel.
Highlights
The cyanobacteria are widely known as producers of a variety of bio-compounds as pigments, are sources of various products such as carotenoids, phycobiliproteins and bioactive compounds as anticancer, antibacterial, antifungal and immunosuppressive agents and lipids [1]
Some studies have reported the urea in the range of 0.8-1.7 g/L, as nitrogen source with the highest potential in obtaining lipids in microalgae cultivation under certain culture conditions, such as photosynthetic systems [21,22]
Lipids profiles with mixtures of SFAs and MUFAs are recommended for use in biodiesel production, when compared to long-chain polyunsaturated fatty acids [29,30,31,32]
Summary
The cyanobacteria are widely known as producers of a variety of bio-compounds as pigments, are sources of various products such as carotenoids, phycobiliproteins and bioactive compounds as anticancer, antibacterial, antifungal and immunosuppressive agents and lipids [1]. Most products are complex organic compounds with unique structures and cannot be synthesized in the laboratory. For this reason, cyanobacteria are known as "cell factories". According to Francisco et al [4], for sustainable production of bulk oil from microalgae becomes viable it is necessary employ organic substrates sources of low cost, as well as the development of induction technology to the accumulation of lipids in the cell
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