Heterotrophic production of lutein by selected Chlorella strains

Seven Chlorella strains representing three species obtained from culture collections and research laboratories were screened for their potential of heterotrophic production of lutein on two different media (Basal and Kuhl) containing glucose. While both media supported good growth and lutein formation of the seven strains in darkness, higher biomass concentrations and lutein content were achieved on Basal medium. Chlorella protothecoides CS-41 was chosen from the seven strains for further investigation due to its higher productivities of both biomass and lutein. The maximal biomass concentration and lutein content of C. protothecoides cultivated heterotrophically with 9 g L^-1 glucose in a 3.7-L fermentor were respectively 4.6 g dry cells L^-1 and 4.60 mg lutein g^-1 dry cells on Basal medium, and 4.0 g dry cells L^-1 and 4.36 mg lutein g^-1 dry cells on Kuhl medium. The heterotrophic cultivation process was scaled up successfully to 30 L using a fermentor, in which the Basal medium containing 36 g L^-1 glucose was used; the maximal biomass concentration of 16.4 g dry cells L^-1, specific growth rate of 0.92 d^-1,lutein content of 4.85 mg lutein g^-1 dry cells,growth yield of 0.47 g dry cells g^-1 glucose and lutein yield of 1.93 mg lutein g^-1 glucose were respectively achieved. This revised version was published online in August 2006 with corrections to the Cover Date.     

Production of lactic acid and byproducts from waste potato starch by <Emphasis Type="Italic">Rhizopus arrhizus</Emphasis>: role of nitrogen sources

Summary Lactic acid was produced by Rhizopus arrhizus using waste potato starch as the substrate. The aim of this study was to identify the role of nitrogen sources and their impact on the formation of lactic acid and associated byproducts. Ammonium sulphate, ammonium nitrate, urea, yeast extract and peptone were assessed in conjunction with various ratios of carbon to nitrogen (C:N). Fermentation media with a low C:N ratio enhanced the production of lactic acid, biomass and ethanol, while a high C:N ratio favoured the production of fumaric acid. Ammonium nitrate appeared to be the most suitable nitrogen source for achieving a high and stable lactic acid yield, and minimizing the production of byproducts such as biomass and ethanol, while urea proved to be the least favourable nitrogen source. Yeast extract and peptone appeared to improve fungal cell growth. The kinetics data revealed that a high concentration of ammonium nitrate enhanced the lactic acid productivity. The maximum lactic acid concentration of 36.4 g/l, representing a yield of 91%, was obtained with addition of 0.909 g/l ammonium nitrate in 32 h.     

High-yield production of lutein by the green microalga Chlorella protothecoides in heterotrophic fed-batch culture

The green microalga Chlorella protothecoides was grown heterotrophically in batch mode in a 3.7-L fermenter containing 40 g/L glucose and 3.6 g/L urea. In the late exponential phase, concentrated nutrients containing glucose and urea were fed into the culture, in which the nitrogen source was sufficient compared to carbon source. As a result, a maximum cell dry weight concentration of 48 g/L was achieved. This cell dry weight concentration was 28.4 g/L higher than that obtained in batch culture under the same growth conditions. In another cultivation run, the culture was provided with the same initial concentrations of glucose (40 g/L) and urea (3.6 g/L) as in the batch mode, followed by a relatively reduced supply of nitrogen source in the fed-batch mode to establish a nitrogen-limited culture. Such a modification resulted in an enhanced lutein production without significantly lowering biomass production. The cellular lutein content was 0.27 mg/g higher than that obtained in the N-sufficient culture. The improvements were also reflected by higher maximum lutein yield, lutein productivity, and lutein yield coefficient on glucose. This N-limited fed-batch culture was successfully scaled up from 3.7 L to 30 L, and a three-step cultivation process was developed for the high-yield production of lutein. The maximum cell dry weight concentration (45.8 g/L) achieved in the large fermenter (30 L) was comparable to that in the small one (3.7 L). The maintenance of the culture at a higher temperature (i.e., 32 degrees C) for 84 h resulted in a 19.9% increase in lutein content but a 13.6% decrease in cell dry weight concentration as compared to the fed-batch culture (30 L) without such a treatment. The enhancement of lutein production resulted from the combination of nitrogen limitation and high-temperature stress.     

Production of biomass and lutein by Chlorella protothecoides at various glucose concentrations in heterotrophic cultures

The influence of initial glucose concentrations on the production of biomass and lutein by Chlorella protothecoides CS-41 was investigated in batch cultures using both shake flasks and fermentors. The maximum biomass concentration increased from 4·9 to 31·2 g litre⁻¹ dry cells with an increase in initial glucose concentration from 10 to 80 g litre⁻¹. An even higher initial glucose concentration (100 g litre⁻¹) resulted in a lower biomass concentration, a lower specific growth rate, a lower growth yield coefficient and a considerably longer lag phase, which might be due to substrate inhibition. The initial glucose level also had a significant effect on the production of lutein. In a 3·7-litre fermentor an increase in lutein production from 19·39 to 76·56 mg litre⁻¹ was obtained with an increase in initial glucose concentration from 10 to 40 g litre⁻¹, within which range, lutein yield coefficient was constant (Y_Itn=1·90±0·02 mg g⁻¹). A simple substrate inhibition model was developed, which fitted the experimental data better than the classical Haldane model. A group of time-dependent kinetic models for algal cultivation in fermentors were also constructed, which were in good agreement with the experimental results and could be employed to predict the production of biomass and lutein, and the consumption of glucose in fermentor cultures.     

High quality biodiesel production from a microalga Chlorella protothecoides by heterotrophic growth in fermenters

The aim of the study was to obtain high quality biodiesel production from a microalga Chlorella protothecoids through the technology of transesterification. The technique of metabolic controlling through heterotrophic growth of C. protothecoides was applied, and the heterotrophic C. protothecoides contained the crude lipid content of 55.2%. To increase the biomass and reduce the cost of alga, corn powder hydrolysate instead of glucose was used as organic carbon source in heterotrophic culture medium in fermenters. The result showed that cell density significantly increased under the heterotrophic condition, and the highest cell concentration reached 15.5 g L(-1). Large amount of microalgal oil was efficiently extracted from the heterotrophic cells by using n-hexane, and then transmuted into biodiesel by acidic transesterification. The biodiesel was characterized by a high heating value of 41 MJ kg(-1), a density of 0.864 kg L(-1), and a viscosity of 5.2 x 10(-4) Pa s (at 40 degrees C). The method has great potential in the industrial production of liquid fuel from microalga.     

不同种类无机盐对灰毡毛忍冬“渝蕾1号”悬浮培养体系中细胞生长和绿原酸含量的影响

为提高灰毡毛忍冬"渝蕾1号"悬浮培养体系中绿原酸的含量,该研究探讨了B_5培养基中不同浓度的无机盐对灰毡毛忍冬"渝蕾1号"悬浮培养细胞生物量及绿原酸含量的影响,通过在悬浮培养体系中添加不同浓度的无机盐,采用重量法测定灰毡毛忍冬"渝蕾1号"悬浮培养细胞的生物量及采用高效液相色谱法测定绿原酸的含量。结果表明:当硝态氮和铵态氮配比与B_5培养基中硝态氮和铵态氮配比一致时,即NO_3~-/NH_4~+摩尔比值为13∶1时,培养体系有利于细胞的生长和绿原酸的积累。当KNO_3浓度为3.5 g·L~(-1)时,细胞生物量达到最大,为19.26 g·L~(-1);当KNO_3在较低浓度(0.5 g·L~(-1)和1.5 g·L~(-1))时,积累较多的绿原酸。NO_3~-的两项研究结果均与对照浓度(2.5g·L~(-1))有一定的差异。另外,对(NH_4)_2SO_4来说,在高于对照浓度0.134 g·L~(-1),即浓度为0.268 g·L~(-1)时,生物量和绿原酸含量都达到了最大。P、Ca、Mg三种矿质元素的研究结果表明,当Na H_2PO_4·2H_2O浓度为0.10 g·L~(-1)、Ca Cl_2的浓度为0.20 g·L~(-1)时,细胞的生长和绿原酸的积累均可达到最大值;而对Mg~(2+)来说,低浓度促进细胞的生长,高浓度促进绿原酸的积累。兼顾细胞生物量和绿原酸含量两个指标,需选择适中的浓度。这些结果均与对照浓度有一定的差异。这说明灰毡毛忍冬"渝蕾1号"悬浮细胞所需无机盐的浓度与B_5培养基无机盐的浓度有一定的差异,选择适宜的浓度可促进其悬浮细胞的生长及次生代谢产物绿原酸的积累。该研究结果为绿原酸的工业化生产打下了基础。     

Effect of nitrogen source on biomass and bioactive compound production in submerged cultures of Eleutherococcus koreanum Nakai adventitious roots

Ammonium to nitrate ratios of 0:30, 5:25, 10:20, 15:15, 20:10, 25:5, and 30:0 mM were tested to determine the optimal NH(4)(+) :NO(3)(-) ratio for improving biomass and bioactive compound production in Eleutherococcus koreanum Nakai adventitious roots using 3-L bulb-type bubble bioreactors. A high ammonium nitrogen ratio had a negative effect on root growth, and the highest fresh and dry weights were obtained when NH(4)(+):NO(3)(-) ratios were 5:25 and 10:20 (mM) after 5 weeks of culture. Although the total production of eleutherosides B and E was slightly higher at the 10:20 ratio than at the 5:25 ratio (NH(4)(+):NO(3)(-)), we proposed that the optimal NH(4)(+):NO(3)(-) ratio was 5:25 mM. This ratio achieved both the highest total production of five target bioactive compounds (eleutherosides B and E, chlorogenic acid, total phenolics, and flavonoids) and the highest root biomass. Furthermore, increasing NH(4)(+):NO(3)(-) ratios to 10:20 decreased pH in the medium, interrupted the absorption of essential minerals from the culture medium, and resulted in low biomass and increased relative oxidative stress levels, which were evaluated by determining 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity. Therefore, nitrate rather than ammonium nitrogen was more essential not for only biomass production but also for bioactive compound production in E. koreanum adventitious root cultures. The optimal nitrogen source ratio produced 5.63 g L(-1) of biomass and 24.41 mg of the five total bioactive compounds per gram of biomass (dry weight basis). The development of such in vitro culture technology will benefit the pilot-scale production of E. koreanum-based bioactive compounds for commercialization.     

氯嘧磺隆与尿素对土壤微生物生物量碳、氮及无机氮的影响

通过室内培养试验,研究了不同浓度氯嘧磺隆(20、200、2000 μg·kg-1土)单一施用及与尿素(120 mg· kg-1土)配合施用情况下,土壤微生物生物量碳、氮和土壤铵态氮、硝态氮随时间的动态变化规律.结果表明:各浓度氯嘧磺隆单独处理在整个培养期(60 d)中对微生物生物量碳、氮均有抑制作用,且浓度越高,后期抑制作用越强;各浓度氯嘧磺隆处理在培养前期对硝态氮、铵态氮没有明显影响,中期(15 d)能显著提高土壤中铵态氮的含量,后期(30 d后)显著提高了土壤中硝态氮的含量.尿素单独施用及与氯嘧磺隆配施均能在短时间内增加微生物生物量碳、氮,但随后配施处理的促进作用减弱;尿素单独和配施均能持久增加土壤中铵态氮、硝态氮含量.     

Biotransformation of phosphogypsum in media containing different forms of nitrogen

Studies on the biotransformation of phosphogypsum (a waste product formed in the course of the production of phosphorous fertilizers) with the use of sulfate reducing bacteria (SRB) demonstrated that it is a good source of sulfates and biogenic elements for these bacteria, though the addition of organic carbon and nitrogen is necessary. The aim of this study was to investigate the form of nitrogen and C:N ratio in the medium on the growth of SRB community in cultures containing phosphogypsum. Batch community cultures of sulfate reducing bacteria were maintained in medium with phosphogypsum (5.0 g/l), different concentrations of sodium lactate (1.6 - 9.4 g/l) and different forms (NH4CI, CO(NH2)2, KNO3) and concentrations (0 - 250 mg/l) of nitrogen. The growth of SRB was studied in the C:N ratio of from 2:1 to 300:1. It was found that: 1 - the best source of nitrogen for SRB is urea, followed by ammonium, the worst were nitrates; 2 - the bacteria were also able to grow in medium without nitrogen but their activity was then by approximately 15% lower than in optimal growth conditions; 3 - in medium with KNO3 inhibition of sulfate reduction by approx. 50% was observed; 4 - the highest reduction of nitrates (removal of nitrate) in media with phosphogypsum and nitrates was at limiting concentrations of sodium lactate. This is probably caused by the selection under these conditions (low concentration of hydrogen sulfide) of denitrifying bacteria or sulfate reducing bacteria capable of using nitrates as an electron acceptor.     

Heterotrophic high cell-density fed-batch cultures of the phycocyanin-producing red alga Galdieria sulphuraria

Growth and phycocyanin production in batch and fed-batch cultures of the microalga Galdieria sulphuraria 074G, which was grown heterotrophically in darkness on glucose, fructose, sucrose, and sugar beet molasses, was investigated. In batch cultures, specific growth rates and yields of biomass dry weight on the pure sugars were 1.08-1.15 day-1 and 0.48-0.50 g g-1, respectively. They were slightly higher when molasses was the carbon source. Cellular phycocyanin contents during the exponential growth phase were 3-4 mg g-1 in dry weight. G. sulphuraria was able to tolerate concentrations of glucose and fructose of up to 166 g L-1 (0.9 M) and an ammonium sulfate concentration of 22 g L-1 (0.17 M) without negative effects on the specific growth rate. When the total concentration of dissolved substances in the growth medium exceeded 1-2 M, growth was completely inhibited. In carbon-limited fed-batch cultures, biomass dry weight concentrations of 80-120 g L-1 were obtained while phycocyanin accumulated to concentrations between 250 and 400 mg L-1. These results demonstrate that G. sulphuraria is well suited for growth in heterotrophic cultures at very high cell densities, and that such cultures produce significant amounts of phycocyanin. Furthermore, the productivity of phycocyanin in the heterotrophic fed-batch cultures of G. sulphuraria was higher than is attained in outdoor cultures of Spirulina platensis, where phycocyanin is presently obtained.     

Different nitrogen sources and growth responses of Spirulina platensis in microenvironments

Spirulina platensis was cultivated, in comparative studies, using several sources of nitrogen. The standard source used (sodium nitrate) was the same as that used in the synthetic medium Zarrouk, whereas the alternative nitrogen sources consisted of ammonium nitrate, urea, ammonium chloride, ammonium sulphate or acid ammonium phosphate. The initial nitrogen concentrations tested were 0.01, 0.03 and 0.05 M in an aerated photobioreactor at 30 °C, with an illuminance of 1900 lux, and 12 h-light/12 h-dark photoperiod over a period of 672 h. Maximum biomass was produced in medium containing sodium nitrate (0.01–0.03–0.05 M), followed by ammonium nitrate (0.01 M) and urea (0.01 M). The final biomass concentrations were 1.992 g l^–1 (0.03 M sodium nitrate), 1.628 g l^–1 (0.05 M sodium nitrate), 1.559 g l^–1 (0.01 M sodium nitrate), 0.993 g l^–1 (0.01 M ammonium nitrate) and 0.910 g l^–1 (0.01 M urea). This suggested that it is possible to utilize nitrogen sources other than sodium nitrate for growing S. platensis, in order to decrease the production costs of scaled up projects.     

Optimization of nitrogen for enhanced citric acid productivity by a 2-deoxy D-glucose resistant culture of Aspergillus niger NGd-280

The present investigation is concerned with the optimization of nitrogen for enhanced citric acid productivity by a 2-deoxy D-glucose resistant culture of Aspergillus niger NGd-280 in a 15 l stirred tank bioreactor. Nutrients, especially nitrogen source have a marked influence on citrate productivity because it is an essential constituent of basal cell proteins. Citric acid has been known to be produced when the nitrogen source was the limiting factor. Ammonium nitrate was employed as a nitrogen source in the present study and batch culture experiments were carried out under various concentrations of ammonium nitrate. Specific growth rate was decreased and the biosynthesis of citric acid was delayed at higher concentrations of ammonium nitrate. Specific citric acid production rate was the highest when intracellular ammonium ion concentration was between 2.0 and 3.0 mmol g(-1) cells. Citrate production was however, stopped when intracellular ammonium ion concentration decreased below 1.0 mmol g(-1) cell.     

Heterotrophic growth and nutritional aspects of the diatom Cyclotella cryptica (Bacillariophyceae): effect of nitrogen source and concentration

To investigate the nutritional value of the diatom Cyclotella cryptica Reimann, Lewin, and Guillard as an alternative feed for the use in the aquaculture industry, the heterotrophic growth characteristics, total fatty acids, and the resultant fatty acid profile of the microalga were studied when cultivated with sodium nitrate, ammonium chloride, or urea. All three nitrogen sources supported growth under heterotrophic conditions, and their uptake affected the pH of the cultivation medium, even when buffered. The use of sodium nitrate or urea resulted in a significant increase in the pH of the cultivation media, whereas the use of ammonium chloride caused a minor decrease in the pH of the cultivation media. The maximum specific growth rate was highest when urea and ammonium chloride were supplied at a low concentration; however, the total fatty acid content was not significantly affected (P = 0.101) by the nitrogen source when supplied at 10.7 mM nitrogen. The total fatty acid content and fatty acid profile of C. cryptica was more affected by the growth phase (predominately influenced by the initial nitrogen concentration) than by the source of nitrogen.     

用混合氮源在室外培养产油链带藻的可行性研究

为探索两株链带藻（Desmodesmus sp.T28-1和Desmodesmus sp.NMX451）在室外培养的最优氮源,首先在室内就不同氮源（尿素、硝酸钠、碳酸铵以及尿素和硝酸钠混合氮源）下微藻的生长和油脂积累做了研究,筛选出最优的混合氮源在室外进行了培养的可行性研究。室内研究结果表明两株链带藻在尿素下培养油脂含量最低,在铵氮下培养生物量最低。且NMX451在混合态氮下的油脂产率显著性的高于其他氮源下的油脂产率。对两株链带藻在混合氮源下的脂肪酸组分做进一步分析,结果表明油脂组分适合生物柴油生产要求,估算的生物柴油品质达到国际和国内生产标准。将两株链带藻置于室外140 L柱式反应器中用混合氮源进一步扩大培养,结果表明NMX451比T28-1的油脂含量和油脂产率高,生产成本更低,且脂肪酸组分更适宜生物柴油生产。研究表明用混合氮源在室外培养微藻是非常可行的培养方法,也说明NMX451比T28-1在生物柴油生产方面具有更好的潜力。     

Production of the copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with varied composition using different nitrogen sources with Haloferax mediterranei

The extreme haloarchaea Haloferax mediterranei accumulates poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) without the need for specific precursors. In this study, growth kinetics and PHBV synthesis were characterised under nitrogen-excess and nitrogen-limiting conditions in ammonium and, for the first time, nitrate. With excess nitrogen, ammonium and nitrate cultures generated 10.7 g/L biomass containing 4.6 wt% PHBV and 5.6 g/L biomass with 9.3 wt% PHBV, respectively. Copolymer composition varied with the nitrogen source used: PHBV from ammonium cultures had 16.9 mol% 3-hydroxyvalerate (HV), while PHBV from nitrate cultures contained 12.5 mol% HV. Nitrogen limitation was achieved with carbon-to-nitrogen (C/N) molar ratios of 25 or higher. Nitrogen limitation reduced biomass generation and polymer concentration, but polymer accumulation increased to 6.6 and 9.4% for ammonium and nitrate, respectively, with C/N 42. PHBV composition was also affected and cultures with lower C/N ratios produced richer HV polymers. Copolymer formation was not a uniform process: HV was only detected after a minimum accumulation of 0.45 g/L PHB and lasted for a maximum of 48 h. The understanding of copolymer synthesis and the influence of culture conditions such as the nitrogen source will help in designing novel strategies for the production of PHBV with more regular structure and material properties.

     

Growth kinetics of vitis vinifera cell suspension cultures: I. Shake flask cultures

Vitis vinifera cell suspension cultures carried out in shake flasks were closely examined for biomass growth and cell division in relation to carbohydrate, NH(4), NO(3)PO(4), and dissolved oxygen (DO)consumption. After inoculation, the oxygen uptake rate of the cultures measured on-tine was observed to increase continuously to a maximum value of 3.8 mmol O(2)L(-1)h(-1) at day 7 when cell division ceased and dissolved oxygen reached its lowest level of 17% air saturation. During this first phase of growth, the specific oxygen uptake rate remained constant at approximately 0.6 mmol 02 O(2) g(-1) dw h(-1)or approximately 2.2 mumol O(2), (10(6) cells)(-1) h(-1) whereas dry biomass concentration increased exponentially from 1.5 to 6.0 g dw L(-1). Thereafter, dry biomass concentration increased linearly to approximately 14 g dw L(-1) at day 14 following nitrate and carbohydrate uptake. During this second phase of growth, the biomass wet-to-dry weight ratio was found to increase in an inverse relationship with the estimated osmotic pressure of the culture medium. This corresponded to inflection points in the dry and wet biomass concentration and packed cell volume curves. Furthermore, growth and nutrient uptake results suggest that extracellular ammonium or phosphate ion availability may limit cell division. These findings indicate that cell division and biomass production of plant cell cultures may not always be completely associated, which suggests important new avenues to improve their productivity. (c) 1995 John Wiley & Sons, Inc.     

Biomass and lutein productivity of <Emphasis Type="Italic">Scenedesmus almeriensis</Emphasis>: influence of irradiance,dilution rate and temperature

In this paper, the biomass and lutein productivity of the lutein-rich new strain Scenedesmus almeriensis is modelled versus irradiance and temperature. The results demonstrate that S. almeriensis is a mesophile microorganism with an optimal growth temperature of 35 degrees C, and capable of withstanding up to 48 degrees C, which caused culture death. This strain is also tolerant to high irradiances, showing no signs of photoinhibition even at the maximum irradiance essayed of 1625 microE m(-2) s(-1) accumulating up to 0.55% dry weight (d.wt.) of lutein. The optimal conditions that maximise the biomass productivity also favour the lutein productivity, lutein being a primary metabolite. Maximal biomass and lutein productivities of 0.87 g l(-1) day(-1) and 4.77 mg l(-1) day(-1), respectively, were measured. The analysis of light availability inside the cultures, quantified as average irradiance, demonstrates that the cultures were mainly photo-limited, although photosaturation also took place at high external irradiances. The effect of temperature was also investigated finding that the specific maximal growth rate is modified by the temperature according to the Arrhenius equation. The influence of both light availability and temperature was included in an overall growth model, which showed, as a result, capable of fitting the whole set of experimental data. An overall lutein accumulation rate model was also proposed and used in a regression analysis. Simulations performed using the proposed models show that under outdoor conditions a biomass productivity of 0.95 g l(-1) day(-1) can be expected, with a lutein productivity up to 5.31 mg l(-1) day(-1). These models may be useful to assist the design and operation optimisation of outdoor cultures of this strain.     

Modeling of lutein production by heterotrophic <Emphasis Type="Italic">Chlorella</Emphasis> in batch and fed-batch cultures

Chlorella is a promising alternative resource of lutein (xanthophyll) production as it can be cultivated heterotrophically in fermentors. In this paper, a kinetic model for lutein production by heterotrophic Chlorella pyrenoidosa was developed based on batch cultivations in 250-ml flasks and a 19-l fermentor. The model was validated by experimental data from two fed-batch cultivations performed in the same fermentor. The dynamic behavior of lutein production by C. pyrenoidosa with various concentrations of glucose and nitrogen was analyzed based on the kinetic model. Model-based analyses suggested that glucose concentrations between 5 and 24 g/l and nitrogen concentrations between 0.7 and 12 g/l during the cultivation were favorable for lutein production by heterotrophic C. pyrenoidosa. It also showed that fed-batch cultivations are more suitable for efficient production of lutein than batch ones. The results obtained in this study may contribute to commercial lutein production by heterotrophic Chlorella.     

真盐生植物盐角草对不同氮形态的响应

盐角草(Salicornia europaea L.)是一种喜盐植物,其最佳生长的实现需要200—400 mmol/L NaCl。为了解盐渍环境下盐角草氮素吸收利用特点,在水培添加200或400 mmol/L NaCl情况下,从生长指标,光合参数,根系体积和活力,硝酸还原酶与谷氨酰胺合成酶活力,蛋白、总氮、硝态氮及铵态氮含量等方面检测了硝态氮、铵态氮和尿素3种氮形态对盐角草生长的影响。研究发现以氮摩尔浓度(mmol/L)计,在0.1—400 mmol/L浓度范围进行测试,盐角草在0.1 mmol/L低氮条件下仍能维持生长,同时,抑制盐角草生长的氮浓度域值较高,其中铵态氮、尿素和硝态氮分别为50、50及400 mmol/L。研究结果表明盐角草吸收利用氮素的能力强,对氮素的浓度耐受范围宽,3种氮形态都可作为氮源满足其生长需要,但有效促进生长的效果存在差异,总体顺序从高到低依次为硝态氮、铵态氮和尿素。研究为揭示盐生植物氮吸收利用特点提供了基础数据,对提高盐生植物生产力,指导沿海滩涂生态建设具有一定的指导意义。     

Production of biomass and nutraceutical compounds by Spirulina platensis under different temperature and nitrogen regimes

The cyanobacterium Spirulina platensis has been used by humans because of its nutritional and possibly medicinal effects. Our study evaluated the influence of temperature and nitrogen concentration in the medium on the production of biomass by this cyanobacterium and the biomass composition in protein, lipid and phenolic compounds. We found that at 35 degrees C there was a negative effect on biomass production but a positive effect on the production of protein, lipids and phenolics, the highest levels of these compounds being obtained in Zarrouk's medium containing 1.875 or 2.500 g l(-1) sodium nitrate. Higher biomass densities and productivity were obtained at 30 degrees C than at 35 degrees C, but nitrogen concentration appeared to have no effect on the amount of protein, lipid or phenolics, indicating that at 30 degrees C the concentration of sodium nitrate in Zarrouk's medium (2.50 g l(-1)) can be reduced without loss of productivity, an important cost-saving factor in large-scale cultivation.