The use of macroalgal hydrolysate as a carbon source in the lipid production of the marine heterotrophic dinoflagellate Crypthecodinium AL–05

Abstract

Abstract Crypthecodinium cohnii strains can accumulate significant amounts of lipids with a high fraction of docosahexaenoic acid that is used in pharmaceutical and nutraceutical applications. In this study, macroalgal hydrolysate was used as a low-cost carbon source for the growth of the oleaginous strain Crypthecodinium sp. AL–05 to reduce the cost of its growth and lipid production. The Saudi strain was placed in the genus Crypthecodinium with high statistical support based on the sequences of three concatenated genes (SSU, ITS, and LSU rDNA). Crypthecodinium sp. AL-05 was grown on four different glucose concentrations and three different macroalgal hydrolysate concentrations: 20, 40, and 80 g  l−1. We also used the same concentrations of macroalgal hydrolysate with 10 g  l−1 of four carbon sources: acetic acid, glycerol, glucose, and sugarcane molasses. Glucose (40 g  l−1) gave the best results, followed by 80 g  l−1 macroalgae alone and with glucose or molasses. One-way ANOVA followed by a Bonferroni correction post-hoc test showed that the dry weight of Crypthecodinium sp. AL–05 produced using the following carbon sources: the four concentrations of the pure glucose, 80 g  l−1 macroalgae alone, 40 and 80 g  l−1 macroalgae + glucose, 40 and 80 g  l1 macroalgae + molasses were significantly higher than the other 10 carbon sources tested. Three carbon sources (20 g  l−1 macroalgae with glucose, molasses and acetic acid) produced percentages of lipids that were significantly lower than the other 16 carbon sources. For the first time, our research shows that the dinoflagellate Crypthecodinium AL–05 can be successfully grown on macroalgal hydrolysate, which can be used in industrial processes. Importantly, Crypthecodinium sp. AL–05 grown on 80 g  l−1 macroalgae produced only saturated fatty acids, of which caprylic acid represented 43.45 % of the total fatty acids. Caprylic acid is widely used in industry and pharmaceuticals and the Saudi isolate can be used for its commercial production using macroalgae as a carbon source.