Characterization of cell growth and starch production in the marine green microalga Tetraselmis subcordiformis under extracellular phosphorus-deprived and sequentially phosphorus-replete conditions

Abstract

Microalgal starch is a potential feedstock for biofuel production. Nutrient stress is widely used to stimulate starch accumulation in microalgae. Cell growth and starch accumulation in the marine green microalga Tetraselmis subcordiformis were evaluated under extracellular phosphorus deprivation with initial cell densities (ICD) of 1.5, 3.0, 6.0, and 9.0×10 6 cells mL were all obtained in the culture with the ICD of 3.0× 10 6 cells mL −1 . Appropriate ICD could be used to regulate the intracellular phosphorus concentration and maintain adequate photosynthetic activity to achieve the highest starch productivity, along with biomass and starch concentration. The recovery of phosphorus-deprived T. subcordiformis in medium containing 0.5, 1.0, or 6.0 mM KH 2 PO 4 was also tested. Cell growth and starch accumulation ability could be recovered completely. A phosphorus pool in T. subcordiformis was shown to manipulate its metabolic activity under different environmental phosphorus availability. Though lower starch productivity and starch content were achieved under phosphorus deprivation compared with nitrogen-or sulfur-deprived conditions, the higher biomass and starch concentration make T. subcordiformis a good candidate for biomass and starch production under extracellular phosphorus deprivation.

Phosphite cannot be used as a phosphorus source but is non-toxic for microalgae

“…In agreement with our findings, Dunaliella tertiolecta was reported to grow in a medium lacking P when the culture was started with P-replete cells [41]. A similar behavior was found in Tetraselmis subcordiformis since the intracellular accumulated P, sustained cell growth when extracellular P was absent [42]. T. subcordiformis is related to C. reinhardtii, and its high survival rate under P-deprivation can be explained by the mobilization of internal reserves of Pi from Poly-P molecules, the secretion of periplasmic phosphatases (which can cleave Pi from Pi esters in the immediate environment), the activation of high-affinity Pi uptake and the substitution of phospholipids for glycolipids and sulfolipids [43].…”

Microalgal growth with intracellular phosphorus for achieving high biomass growth rate and high lipid/triacylglycerol content simultaneously

“…4b). Similar phenomenon has also been reported by other researchers (Khozin-Goldberg and Cohen, 2006;Yao et al, 2013).…”

“…These results indicated that in microalgal growth with intracellular phosphorus the algal density growth rate and the biomass growth rate was uncoupled to a certain extent. Similar phenomenon was observed by Yao et al (2013), Zhang and Hong (2014).…”

Accumulation of energy reserves in algae: From cell cycles to biotechnological applications

“…Phosphorus limitation in Chlorella vulgaris slowed dry weight increases and stopped cell division completely after 12 h of growth. The relative content of starch in phosphorus-starved cells (in % of DW) was lower than in sulfur-starved Chlorella vulgaris cells (Brányiková et al, 2011), similar to the marine alga Tetraselmis subcordiformis (Yao et al, 2013;Yao et al, 2012). (Wu et al, 2013).…”