Abstract
<p><em>Botryococcus</em> sp. is one of microalgae species that has a high lipid content as much as 75% of their dry weight. But, lipid production by microalgae is regulated by their environmental condition (pH, light, temperature, nutrition, etc). Mutagenesis induced by Gamma <sup>60</sup>Co irradiation can be utilized to alter the <em>Botryococcus</em> sp. genetic to get microalgae mutant strain that can produce a higher lipid content than the wild strain. <em>Botryococcus</em> sp. was irradiated with different doses of gamma ray of <sup>60</sup>Co (0, 2, 4, 6, and 10 Gy), and the effect on the growth, lipid content, and fatty acid composition of microalgae were observed. Research design used is random complete (RAL) with 95 % confident level for quantitive analysis based on the biomass and lipid contents. More over fatty acid composition was analyzed by Gas Cromatography-Mass Spectrometry<em> </em>(GC-MS). Results showed that Gamma irradiated gave an effect on growth and lipid content of <em>Botryococcus</em> sp. But between the control treatment (0 Gy) with microalgae irradiated dose of 2 Gy, 4 Gy and 6 Gy were not significantly different. Whereas between the control with 10 Gy irradiated was significantly different. The highest biomassa and lipid content are found in 10 Gy irradiated microalgae with 0.833 gram biomass and 41% lipid content. Fatty acid profile of <em>Botryococcus</em> sp. control has 6 fatty acids while 10 Gy irradiated microalgae has 12 fatty acids, with the long-chain fatty acids increased, whereas short-chain fatty acids decreased.</p>
Highlights
Microalgae is an unicelular photosynthetic organism that has great potential in the biotechnology industry, especially as a source of renewable energy (Chisti, 2007; Derner, 2006)
This is similar with research conducted by Sari et al, (2013) that showed Botryococcus sp. had the log growth phase until 1st day of growth, following an exponential phase which in this study occured up to 10th day, a stationary phase for 1 day followed by the decreased in growth
The results of biomass and total lipid analysis in this study showed a different response on Botryococcus sp. irradiated with 2 Gy dose that had higher biomass but lower lipid content than control
Summary
Microalgae is an unicelular photosynthetic organism that has great potential in the biotechnology industry, especially as a source of renewable energy (Chisti, 2007; Derner, 2006). Microalgae can provide several types of renewable energy sources, such as methane produced by anaerobic metabolic process of algae biomass, biodiesel derived from lipid of microalgae and biohidrogen production (Spolaore et al, 2006; Chisti, 2007; Fedorov et al, 2001; Kapdan & Kargi, 2006). Microalgae as a source of biodiesel has the potential to completely replace fossil diesel, because compared to other oil-producing crops, microalgae grows very rapidly and contains high lipid (Spolaore et al, 2006). The production of biodiesel from microalgae is still lacking industrial applicability because it requires a higher cost compared with fossil diesel (Yang et al, 2012)
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