Nutrient Deprivation Coupled with High Light Exposure for Bioactive Chrysolaminarin Production in the Marine Microalga Isochrysis zhangjiangensis

Abstract

Chrysolaminarin, a kind of water-soluble bioactive β-glucan produced by certain microalgae, is a potential candidate for food/pharmaceutical applications. This study identified a marine microalga Isochrysis zhangjiangensis, in which chrysolaminarin production was investigated via nutrient (nitrogen, phosphorus, or sulfur) deprivations (-N, -P, or -S conditions) along with an increase in light intensity. A characterization of the antioxidant activities of the chrysolaminarin produced under each condition was also conducted. The results showed that nutrient deprivation caused a significant increase in chrysolaminarin accumulation, though this was accompanied by diminished biomass production and photosynthetic activity. -S was the best strategy to induce chrysolaminarin accumulation. An increase in light intensity from 80 (LL) to 150 (HL) µE·m−2·s−1 further enhanced chrysolaminarin production. Compared with -N, -S caused more suitable stress and reduced carbon allocation toward neutral lipid production, which enabled a higher chrysolaminarin accumulation capacity. The highest chrysolaminarin content and concentration reached 41.7% of dry weight (%DW) and 632.2 mg/L, respectively, under HL-S, with a corresponding productivity of 155.1 mg/L/day achieved, which exceeds most of the photoautotrophic microalgae previously reported. The chrysolaminarin produced under HL-N (Iz-N) had a relatively competitive hydroxyl radical scavenging activity at low concentrations, while the chrysolaminarin produced under HL-S (Iz-S) exhibited an overall better activity, comparable to the commercial yeast β-glucan, demonstrating I. zhangjiangensis as a promising bioactive chrysolaminarin producer from CO2.

Microbial Interactions between Marine Microalgae and Fungi: From Chemical Ecology to Biotechnological Possible Applications

“…Chrysolaminarin ( Figure 1 ) is a storage polysaccaride, consisting of a β -1,3-linked backbone with infrequent β -1,6-linked branches, typically found in microalgae [ 40 ]. It has been reported, in fact, in the diatoms Phaeodactylum tricornutum and Odontella aurita [ 40 ], in the Chrysophytes Poterioochromonas malhamensis , Isochrysis zhangjiangensis and Isochrysis galbana [ 41 , 42 , 43 ], and in the Eustigmatophyte Nannochloropsis gaditana [ 44 ]. It is a hydrophilic compound, stored in the vacuoles.…”

“…It is a hydrophilic compound, stored in the vacuoles. It has been reported to also reach more than 40% of algal biomass when cultured in specific conditions, such as nutrient deprivation [ 43 ], suggesting a preference for stressful culturing conditions in order to easily accumulate, extract, and purify it [ 40 , 42 ]. Regarding chrysolaminarin bioactivity, it has been reported to exert antioxidant, immunomodulatory, anticancer and regeneration-promoting effects [ 41 , 42 , 45 , 46 ].…”

“…For this reason, the authors proposed this chrysolaminarin-enriched extract as immunostimulating feed in aquaculture [ 46 ]. Thanks to these properties, it is considered a good candidate for food and pharmaceutical applications [ 43 ].…”

Tisochrysis lutea as a Substrate for Lactic Acid Fermentation: Biochemical Composition, Digestibility, and Functional Properties

“…Besides DHA, it also contains other bioactive compounds, such as fucoxanthin [ 25 , 26 ] and phenols [ 27 , 28 ], together with a high amount of proteins and fibres [ 26 ]. The beta-glucan chrysolaminarin is the storage product [ 29 ]. Despite its valuable biochemical profile, T. lutea is not much investigated in the functional food industry, and it is not currently approved for use in food; nevertheless, several studies show its safety as a dietary product.…”