Biomass and Algal Oil Productivity with Fatty Acid Profiles of Botryococcus Sp. Cultures Under Different Concentrations of Nitrogen

Abstract

Objectives: To develop an efficient Botryococcus sp. for high biomass and oil productivity with a fatty acid profile suitable for biodiesel. Methods and analysis: The culture of Botryococcus sp.was maintained in the modified Chu-13 medium at 16:8 light and dark cycle with 5,200 lux light intensity at 25°C and aerated with 1.5 L of air per minute. The nitrogen concentrations of the media varied, 5, 28, 55 (control), 350 mg L −1 , with a constant concentration of phosphorous (44 mg L −1). For growth determination, Botryococcus sp. was harvested, dried, and weighed. Nitrogen consumption was measured by spectrophotometric methods. Oil was extracted from dried biomass of the algae using a soxhlet extractor (70°C, 4 hours), followed by methylation and analysis of fatty acids using gas chromatography. Findings: The results under these sets of experiments indicated that 350 mg N L −1 gave the maximal growth rate i.e. 0.24 g day −1 and the maximal biomass productivity i.e. 77.5 mg L −1 day −1. On the other hand, the maximal oil productivity of 5.03 ± 0.10 mg L −1 d −1 was obtained from medium containing nitrogen 55 mgL −1. The fatty acid profile of Botryococcus sp. oil showed a high amount of palmitic acid and oleic acid. Nitrogen concentrations of 5, 28, 55 (control) and 350 mg L −1 in the culture media resulted in 38.07%, 34.59%, 29.48%, 19.43% palmitic acid and 22.29%, 24.52%, 26.99%, 8.81% oleic acids respectively. These fatty acid profiles indicated that the Botryococcus sp. oil could be processed into biodiesel. Novelty: Growth, oil biomass content and fatty acid profiles of Botryococcus sp. cultures were affected by nitrogen concentration of the media. In this study, 55 mg N L −1 was the most efficient nitrogen concentration for maximal oil productivity with fatty acid content that met the requirements for conversion into biodiesel.