A novel source of dihomo‐γ‐linolenic acid: Possibilities and limitations of DGLA production in the high‐density cultures of the Δ5 desaturase‐mutant microalga Lobosphaera incisa

Abstract

The D5 desaturase mutant (P127) of the microalga Lobosphaera incisa is a promising organism for large-scale production of the valuable LC-PUFA dihomo-g-linolenic acid (DGLA, 20:3 n-6). We examined the potential of P127 for DGLA production under nitrogen (N) starvation conditions, triggering the deposition of DGLA in triacylglycerols, and developed a strategy for optimization of the DGLA productivity in highdensity cultures. Towards this end, the effects of initial biomass concentration (1, 2, and 4 g L À1 ) and PAR irradiance (170 and 400 mmol m À2 s À1 ) on DGLA and total fatty acid (TFA) production were studied. The highest DGLA and TFA percentages (10 and 38% of dry weight, respectively) were displayed by the cultures initiated at 1 g L À1 and grown under a moderate irradiance. Higher irradiances and lower starting biomass content facilitated oleic acid accumulation at the expense of DGLA. Maximum volumetric productivities of TFA and DGLA were recorded in the cultures started at 2 g L À1 biomass and grown under 400 mmol PAR m À2 s À1 . We show that a sufficiently high starting culture density should be combined with a mild light stress to facilitate the production of biomass enriched in DGLA-containing triacylglycerols.Practical applications: The D5 desaturase mutant of L. incisa, P127, is a rare green source of DGLA, a LC-PUFA with valuable pharmaceutical and neutraceutical properties. We report on the optimization of DGLA production by the nitrogen-starving indoor cultures of P127. Stresses, such as N starvation and/or high irradiances, promote accumulation of lipids by microalgal cells. On the other hand, excessively severe stress is deteriorative for the target LC-PUFA accumulation. An important outcome of the present work is establishing physiological constrains of DGLA productivity and finding an approach to balance starting cell density vs. irradiance in order to maximize DGLA yields. Findings of the present work lay a foundation of the efficient production of DGLA using upscaled cultures of P127.

Dietary Supplementation With ω6 LC-PUFA-Rich Algae Modulates Zebrafish Immune Function and Improves Resistance to Streptococcal Infection

“…In this work, zebrafish were fed with experimental diets, in which a certain fraction of the original feed (7.5 and 15%) was replaced with broken biomasses of two strains of the oleagenous microalga L. incisa . The two strains of this microalga accumulate n -6 LC-PUFA as the major component of triacylglycerols, in particular under nitrogen starvation ( 23 , 37 ). Hence, n -6 LC-PUFA-enriched triacylglycerols were the major source of dietary ARA and DGLA, in the WT- and MUT-supplemented diets, respectively.…”

“…However, there are no reports of studies on DGLA dietary supplementation in fish, largely due to limitations in the availability of this rare LC-PUFA. In this context, the microalga Lobosphaera incisa wild type (WT) and its Δ5-desaturase mutant P127 (MUT) are unique photosynthetic sources for ARA and DGLA, respectively ( 22 , 23 ), whose potential in aquaculture nutrition is yet to be explored. Microalgae are an emerging resource for biochemical diversity and various health-promoting ingredients, such as LC-PUFA, carotenoids, exopolysaccharides and more.…”

Acclimation of thermotolerant algae to light and temperature interaction1

“…1). Several studies have already reported an increase in specific growth rates with increasing light supplies (Abu-Ghosh et al 2015b, Ota et al 2015, Gonc ßalves et al 2016). However, in the light-temperature matrix, there was a strong interaction in which the growth dependency on light differed significantly (P < 0.005) between growth temperatures.…”

“…Several studies have already reported an increase in specific growth rates with increasing light supplies (Abu‐Ghosh et al. 2015b, Ota et al. , Gonçalves et al.…”