Fatty acid composition of the thermophilic Gloeocapsa gelatinosa under different combinations of temperature, light intensity, and NaNO3 concentration

Abstract

The combined effect of temperature, light intensity, and NaNO3 concentration on lipid biosynthesis and fatty acid composition was investigated for the thermophilic cyanobacterium Gloeocapsa gelatinosa (Kutzing 1843) isolated from a thermal spring in Tunisia. Under optimal growth conditions, the lipid content was 7.3 % DW. Fatty acid analysis revealed the predominance of 16:0 and 18:0 (23.7 and 18.2 %, respectively) as main straight carbon chains of saturated fatty acids. Unsaturated fatty acids were also identified with 18:1n9c (18.8 %) and 16:1n7 (5 %) being the predominant components. The effect of environmental factors on fatty acid composition was monitored by using principal component analysis and central composite design. Variation of light intensity (20 to 150 μmol photons m−2 s−1), temperature (20 to 60 °C), and nitrogen concentration (0 to 3 g L−1) induced a significant variation in the amount of fatty acid proportions, whereas lipid content was only slightly modified. Results showed that light intensity had the strongest effect on the composition of fatty acids. Temperature had a synergic effect with light intensity while nitrogen concentration had a trivial effect. The combined effect of high light intensity (150 μmol photons m−2 s−1) and high temperature (60 °C) increased the proportion of saturated 16:0 and 18:0 fatty acids along with long-chain fatty acids to 82 % which was twofold higher than that in optimal growth conditions. This induced fatty acid profile makes G. gelatinosa-based biofuels adaptable for higher energetic efficiency and higher oxidative stability.