Production of Carotenoids and Phospholipids by Thraustochytrium sp. in Batch and Repeated-Batch Culture

Abstract

The carotenogenic thraustochytrid Thraustochytrium sp. RT2316-16 was grown in batch and repeated-batch cultures using different feeds containing glucose, or glycerol, and yeast extract, for the production of lipids, phospholipids and carotenoids. RT2316-16 produced canthaxanthin, astaxanthin and β-carotene. The effects of biotin, ascorbic acid, light and temperature were evaluated in some of the experiments. In 2-day-old batch cultures, the combined mass percentage of eicosapentaenoic acid and docosahexaenoic acid in total lipids was between 16.5% (glycerol-based medium in the dark; biomass concentration = 4.2 ± 1.1 g L−1) and 42.6% (glucose-based medium under light; biomass concentration = 3.3 ± 0.1 g L−1), decreasing to 3.8% and 6.1%, respectively, after day 4. In repeated-batch cultures, the total lipids in the biomass increased after glucose or glycerol was fed alone, whereas the total carotenoids (168 ± 7 μg g−1 dry weight (DW)) and phospholipids in the biomass increased after feeding with yeast extract. The biomass with the highest content of phospholipids (28.7 ± 4.3 mg g−1 DW) was obtained using a feed medium formulated with glycerol, yeast extract and ascorbic acid. Glycerol was the best carbon source for the production of a biomass enriched with total lipids (467 ± 45 mg g−1 DW). The composition of carotenoids depended strongly on the composition of the feed. Repeated-batch cultures fed with yeast extract contained canthaxanthin as the main carotenoid, whereas in the cultures fed only with glucose, the biomass contained mainly β-carotene.

Nitrogen Sources Affect the Long-Chain Polyunsaturated Fatty Acids Content in Thraustochytrium sp. RT2316-16

“…After this initial period, the carotenoid content increased, but in some cases, there was a loss in carotenoids towards the end of the culture. This concurred with earlier work in repetitive batch culture that had shown both the carotenoid content and composition to be influenced by the composition of the culture medium used to grow the biomass [ 6 ]. A medium rich in yeast extract promoted the accumulation of carotenoids in the biomass.…”

“…As a first objective, the effects of the different media components (glucose, yeast extract, and glutamate) on the production of biomass and lipids by RT2316-16 were elucidated. The basal medium M is comprised of glucose (20 g L −1 ), yeast extract (6 g L −1 ), and monosodium glutamate (0.6 g L −1 ) (0.52 g L −1 glutamic acid) [ 6 , 9 , 10 ]. As shown in Figure 1 , eliminating glutamate from this medium had no significant effect ( p > 0.05) on the biomass concentration (4.4 ± 0.1 g L −1 and 4.2 ± 0.6 g L −1 with and without glutamate, respectively).…”

“…The observed loss of total lipids and carotenoids during early incubation was nearly simultaneous ( Figure 3 and Figure 4 ), suggesting that these processes were somehow linked. The main carotenoid produced by RT2316-16 is β-carotene [ 6 ], a lipophilic molecule that is apportioned between the cell membranes and the lipid droplets. The initial loss of total carotenoids may have been due to β-oxidation of fatty acids, that lowers the total quantity (number and size) of lipid droplets.…”

“…Thraustochytrium sp. RT2316-16 [ 6 , 16 ] was used in all experiments. The stock cultures were stored in glycerol (50% v/v ) at −18 °C.…”

“…RT2316-16 is a psychrophilic marine protist that does not grow at temperatures exceeding 15 °C. RT2316-16 produces carotenoids (β-carotene, canthaxanthin and astaxanthin) and lipids that contain EPA and DHA [ 6 ]. Carotenoids, such as β-carotene (a precursor of vitamin A in humans), are essential nutrients for humans.…”