EFFECTS OF HARVEST STAGE AND LIGHT ON THE BIOCHEMICAL COMPOSITION OF THE DIATOM THALASSIOSIRA PSEUDONANA¹

Abstract

The marine diatom Thalassiosira pseudonana (Hustedt, clone 3H) Hasle and Heimdal was cultured under three different light regimes: 100 μmol photon · m−2· s−1 on 12:12 h light : dark (L:D) cycles; 50 μmol photon · m−2· s−2 on 24:0 h L:D; and 100 μmol photon · m−2· s−1 on 24:0 h L:D. It was harvested during logarithmic and stationary phases for analysis of biochemical composition. Across the different light regimes, protein (as % of organic weight) was highest in cells during logarithmic phase, whereas carbohydrate and lipid were highest during stationary phase. Carbohydrate concentrations were most affected by the different light regimes; cells grown under 12:12 h L:D contained 37–44% of the carbohydrate of cells grown under 24:0 h L:D. Cells in logarithmic phase had high proportions of polar lipids (79 to 89% of total lipid) and low triacylglycerol (≤10% of total lipid). Cells in stationary phase contained less polar lipid (48 to 57% of total lipid) and more triacylglycerol (22 to 45% of total lipid). The fatty acid composition of logarithmic phase cells grown under 24:0 h L:D were similar, but the 100 μmol photon · m−2· s−1 (12:12 h L:D) cells at the same stage contained a higher proportion of polyunsaturated fatty acids (PUFAs) and a lower proportion of saturated and monounsaturated fatty acids due to different levels of 16:0, 16:1(n‐7), 16:4(n‐1), 18:4(n‐3), and 20:5(n‐3). With the onset of stationary phase, cells grown at 100 μmol photon · m−2· s−1 (both 12:12 and 24:0 h L:D) increased in proportions of saturated and monounsaturated fatty adds and decreased in PUFAs. Concentrations (% organic or dry weight) of 14:0, 16:0, 16:1(n‐7), 20:5(n‐3), and 22:6(n‐3) increased in cells of all cultures during stationary phase. The amino acid compositions of cells were similar irrespective of harvest stage and light regime. For mariculture, the recommended light regime for culturing T. pseudonana will depend on the nutritional requirements of the animal to which the alga is fed. For rapidly growing bivalve mollusc larvae, stationary‐phase cultures grown under a 24:0 h L:D regime may provide more energy by virtue of their higher percentage of carbohydrate and high proportions and concentrations of energy‐rich saturated fatty acids.

Acyl lipid composition variation related to culture age and nitrogen concentration in continuous culture of the microalga Phaeodactylum tricornutum

“…Probably, this state represents an`optimum' for P. tricornutum cells as suggested by the fact that biomass productivity reached a maximum at this dilution rate; the biomass productivity decreased when culture was moved in either direction from this optimum point (data not shown). A reduction in polar lipids and an increase in TAG are usually associated with culture ageing (A Â lvarez Cobelas, 1989;Hodgson et al, 1991;Dunstan et al, 1993;Lombardi and Wangersky, 1995;Brown et al, 1996), however, the speci®c response may be dierent in dierent microalgae (Lombardi and Wangersky, 1995), or the response may depend on the steady state reached as shown in this work. When dilution rate increases (i.e.…”

Effects of prolonged darkness and temperature on the lipid metabolism in the benthic diatom Navicula perminuta from the Arctic Adventfjorden, Svalbard

“…Comparison with other studies indicate, that the relative composition of the individual lipid classes in diatoms depend on species, growth conditions, growth phase and also on extraction methods (Volkman et al 1989;Parrish and Wangersky 1990;Dunstan et al 1994;Berge et al 1995;Brown et al 1996;Lynn et al 2000). Concentrations of FFA are highly species specific and can range from 0.4 to 26% of total lipids (Volkman et al 1989;Parrish et al 1991;Dunstan et al 1994).…”

“…Would the FFA content be a source of artefacts, the relative concentration should be constant throughout the experiment. The TAG concentration in diatoms ranges from 0.3 to 47.7% of total lipids (Volkman et al 1989;Dunstan et al 1994) and depends on nutrient availability, irradiance, growth phase and medium, salinity, pH and temperature (Brown et al 1996;Lynn et al 2000;Hu et al 2008;Obata et al 2013). The thylakoid membrane of diatoms consists of the same lipid classes like in vascular plants (Goss and Wilhelm 2010) and green algae (Vieler et al 2007) with the difference that diatoms have a much higher content of negatively charged lipids, such as SQDG and PG (Vieler et al 2007;Goss et al 2009).…”

Microalgal triacylglycerols as feedstocks for biofuel production: perspectives and advances

“…Typically, low light intensity induces the formation of polar lipids, particularly the membrane polar lipids associated with the chloroplast, whereas high light intensity decreases total polar lipid content with a concomitant increase in the amount of neutral storage lipids, mainly TAGs (Brown et al, 1996;Khotimchenko and Yakovleva, 2005;Napolitano, 1994;Orcutt and Patterson, 1974;Spoehr and Milner, 1949;Sukenik et al, 1989).…”