Effects of light intensity and the remaining nitrate concentration on the beta-carotene accumulation of a wild Dunaliella salina strain isolated from the saline soil

Abstract

An isolated <em>Dunaliella salina</em> strain from northern Thailand was cultured in modified Johnson’s medium in column photobioreactor. The beta-carotene accumulation mainly depended on the quantities of cells entering into carotenogenesis condition that was significantly enhanced by high started KNO3 concentration. Low remaining nitrate concentration in the culture of each cell (RNCC) was suitable for algae to accumulate beta-carotene. Following the cultivation time extended, RNCC of all cultures decreased and tended to the same level (10-20 pg/cell) although the biomass or betacarotene content in the culture was higher in high started KNO3 concentration. High light intensity restrained the growth especially in low KNO3 concentration but improved betacarotene accumulation and RNCC. The highest biomass and beta-carotene dry weight (DW) were 2.25 g L-1 and 79.2 mg g-1 DW respectively. Above results indicated that increasing the biomass and as early as possible to strengthen the stress on each cell was important to improve the final beta-carotene yield.

Effects of phosphorus on the growth and chlorophyll fluorescence of a Dunaliella salina strain isolated from saline soil under nitrate limitation

“…Obviously, high phosphate concentration could retard the decrease of Fv/Fm value (Figure 2). In addition, by comparing our previous researches, 15,24,27 the cell densities of KU XI was up to 8×10 4 mL -1 which was far higher than the result in this study when nitrate above 0.5 g L -1 . Thus the transition of restrained algae growth was changed from phosphorus to nitrogen when NaH2PO4 concentration was lower 12.1 µM or higher 72.6 µM (Figure 1).…”

“…When light intensity was held constant, it is possible to describe the maximum growth rate solely as a function of temperature by applying the Arrhenius equation: 23 µm=Ae -E/RT (eq. 3) in which A was constant; E was activation energy, cal mol -1 ; R was universal gas constant, cal K -1 mol -1 ; and T was temperature, Kelvin scale, K. According to the growth rate of KU XI at different temperature, 15,16,24 an equation could be obtained: µm=1.26×10 6 e -4419/T . Thus, eq.4 could be as follows:…”

“…7,14 Due to the different living environments of D. salina strains, their optimal conditions for growth and pigments accumulation are different. 15,16 D. salina strain in this study was isolated from saline soils in northeastern Thailand where nearly 17% of this area is covered by saline-alkaline soil and unsuited for agricultural plantation. 15 Developing algal industry in this area by using the local algae species would be a valid and economic strategy.…”

Outdoor cultivation of Dunaliella salina KU 11 using brine and saline lake water with raceway ponds in northeastern Thailand

“…Our results showed that high KNO 3 and NaHCO 3 concentrations could significantly improve cell quantities, but the highest beta‐carotene content per cell was not found for this combination (Table ). Our previous investigation using indoor cultivation showed that beta‐carotene content per cell of D. salina KU 11 ranged from 5 to 13 pg/cell, which was lower than for outdoor production . The lower per cell levels of beta‐carotene for indoor cultivation may relate to the higher cell densities and decreased light intensity for each cell under indoor conditions.…”

Transcription Factor OsDOF18 Controls Ammonium Uptake by Inducing Ammonium Transporters in Rice Roots

“…At 14 days after germination (DAG), the seedlings were transferred to a glass tube containing 4 ml of Yoshida medium ( Yoshida et al, 1976 ) that contains both ammonium and nitrate as the N source. Medium was harvested at 2-d intervals during the nitrogen uptake experiments, and ammonium and nitrate levels were determined with a UV-1800 spectrometer (Shimadzu, Japan) at OD 625 and OD 220 , respectively ( Martín-Rodríguez et al, 2015 ; Weatherb, 1967 ; Wu et al, 2015 ).…”