Tolerance of Tetraselmis tetrathele to High Ammonium Nitrogen and Its Effect on Growth Rate, Carotenoid, and Fatty Acids Productivity

Abstract

Microalgae can use either ammonium or nitrate for its growth and vitality. However, at a certain level of concentration, ammonium nitrogen exhibits toxicity which consequently can inhibit microalgae productivity. Therefore, this study is aimed to investigate the tolerance of Tetraselmis tetrathele to high ammonium nitrogen concentrations and its effects on growth rate, photosynthetic efficiency (Fv/Fm), pigment contents (chlorophyll a, lutein, neoxanthin, and β-carotene), and fatty acids production. Experiments were performed at different ammonium nitrogen concentrations (0.31–0.87 gL−1) for 6 days under a light source with an intensity of 300 μmol photons m−2 s−1 and nitrate-nitrogen source as the experimental control. The findings indicated no apparent enhancement of photosynthetic efficiency (Fv/Fm) at high levels of ammonium nitrogen (NH4+-N) for T. tetrathele within 24 h. However, after 24 h, the photosynthetic efficiency of T. tetrathele increased significantly (p < 0.05) in high concentration of NH4+-N. Chlorophyll a content in T. tetrathele grown in all of the different NH4+-N levels increased significantly compared to nitrate-nitrogen (NO3-N) treatment (p < 0.05); which supported that this microalgal could grow even in high level of NH4+-N concentrations. The findings also indicated that T. tetrathele is highly resistant to high ammonium nitrogen which suggests T. tetrathele to be used in the aquaculture industry for bioremediation purpose to remove ammonium nitrogen, thus reducing the production cost while improving the water quality.

Intensive production of the harpacticoid copepod Tigriopus californicus in a zero-effluent ‘green water’ bioreactor

“…To carry out the latter, the resident microbial ecosystem constantly reduced the levels of nitrogen, phosphorus and metals in the water, even in the presence of the fecal pellets of Tigriopus 43 . Although we cannot conclude with the work described here, we hypothesize that the high capacity of Tetraselmis to remove nitrogen from water 26 , 27 was essential in this task. Thus, we simply had to periodically add nitrate, phosphate, metals and vitamins to keep the microalgae fit.…”

“…Tetraselmis is a marine microalgae widely used in aquaculture for its high nutritional value 24 . Recently, the large-scale production of this genus has been reported in industrial photobioreactors 25 , and its bioremediation capabilities, both in aquaculture 26 and in domestic wastewater 27 are very promising. Furthermore, Tetraselmis can grow in reused culture media 28 or even benefit from them 29 .…”

CO2-Inorganic Carbon Auto-Buffering System for Efficient Ammonium Reclamation Coupled with Valuable Biomass Production in a Euryhaline Microalga Tetraselmis subcordiformis

“…+ was dominant and hence greatly reduced the probability of the stripping. In fact, the estimation of free ammonia (NH 3 ) relative to the total ammonia (NH 3 and NH 4 + ) in the medium according to the formula of NH 3 (%) = 100/(1 + [H + ]/K a ), where K a is the dissociation constant of ammonia (4.36 × 10 −10 at 25 • C in seawater) [13,51], showed that free ammonia accounted for maximally 42~65% in the ICs as against less than 8% in the CO 2 -ICs (Figure S2a). Therefore, the CO 2 -IC system allowed much less N escape than the IC systems.…”

“…The most critical challenge is the pH decrease during the NH 4 + assimilation owing to the excretion of H + , which causes the diminished photosynthesis and deteriorates the removal [10,11]. To stabilize the pH, organic buffering agents (e.g., Tricine, TAPS) or on-site pH monitoring/adjustment systems are usually applied, which can introduce extra CODs and increase operation facilities and costs [12][13][14]. The addition of alkaline inorganic bicarbonate (mainly NaHCO 3 ) is an alternative strategy to abate the acidification of the NH 4 + removal process by simultaneously providing a carbon source for microalgae to meet the proper C/N ratio in the wastewater treatment [12,15].…”

“…This strain is a euryhaline green microalga capable of acclimating to a wide salinity range (5.4~67.5 g/L NaCl) [20] and is assumed to be resistant to the fluctuations of salinity in urban wastewaters, especially those originated from coastal or island areas where seawater is used for toilet flushing or the intrusion of seawater into the wastewater often occurs [21]. The genus Tetraselmis has been reported to tolerate high NH 4 + -N and have an excellent capability of apparent NH 4 + -N removal from varied types of wastewater, including urban wastewater [4,13,22,23], but the processes were generally run without pH control (Table 1), or with a pH stat system or manual adjustment by acid/base, or buffered with organic agents (such as Tricine) [13,23,24]. The proportion of NH 4 + -N that was incorporated into the microalgae biomass or escaped from the culture system, which was the essential index to assess the NH 4 + -N bioconversion efficiency, remained undetermined in these processes.…”