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1.
Kinetic models for astaxanthin production by high cell density mixotrophic culture of the microalga Haematococcus pluvialis 总被引:3,自引:0,他引:3
High cell density cultivation of Haematococcus pluvialis for astaxanthin production was carried out in batch and fed-batch modes in 3.7-L bioreactors with stepwise increased light
intensity control mode. A high cell density of 2.65 g L−1 (batch culture) or 2.74 g L−1 (fed-batch culture) was obtained, and total astaxanthin production in the fed-batch culture (64.36 mg L−1) was about 20.5% higher than in the batch culture (53.43 mg L−1). An unstructured kinetic model to describe the microalga culture system including cell growth, astaxanthin formation, as
well as sodium acetate consumption was proposed. Good agreement was found between the model predictions and experimental data.
The models demonstrated that the optimal light intensity for mixotrophic growth of H. pluvialis in batch or fed-batch cultures in a 3.7-L bioreactor was 90–360 μmol m−2 s−1, and that the stepwise increased light intensity mode could be replaced by a constant light intensity mode.
Received 24 December 1998/ Accepted in revised form 23 April 1999 相似文献
2.
The green microalga Chlorella zofingiensis can produce the ketocarotenoid astaxanthin under heterotrophic culture conditions. Here we report the growth-associated biosynthesis
of astaxanthin in this biotechnologically important alga. With glucose as sole carbon and energy source, C. zofinginesis grew fast in the dark with rapid exhaustion of nitrogen and carbon sources from media, leading to a high specific growth
rate (0.034 h−1). Cultures started at a cell concentration of about 3.4 × 109 cells l−1 reached, after 6 days, standing biomass values of 1.6 × 1011 cells or 8.5 g dry weight l−1. Surprisingly, the biosynthesis of astaxanthin was found to start at early exponential phase, independent of cessation of
cell division. A general trend was observed that the culture conditions benefiting cell growth also benefited astaxanthin
accumulation, indicating that astaxanthin was a growth-associated product in this alga. The maximum cell dry biomass and astaxanthin
yield were 11.75 g l−1 and 11.14 mg l−1 (about 1 mg g−1), simultaneously obtained in the fed-batch culture with a combined glucose–nitrate mixture addition, which were the highest
ever reported in dark-heterotrophic algal cultures. The possible reasons why dark-heterotrophic C. zofingiensis could produce astaxanthin during the course of cell growth were discussed. 相似文献
3.
Increased astaxanthin production by a Phaffia rhodozyma mutant grown on date juice from Yucca fillifera 总被引:1,自引:0,他引:1
J Ramírez M L Nuñez R Valdivia 《Journal of industrial microbiology & biotechnology》2000,24(3):187-190
The wild strain and the astaxanthin-overproducing mutant strain 25–2 of Phaffia rhodozyma were analyzed in order to assess their ability to grow and synthesize astaxanthin in a minimal medium composed of g L−1: KH2PO4 2.0; MgSO4 0.5; CaCl2 0.1; urea 1.0 and supplemented with date juice of Yucca fillifera as a carbon source (yuca medium). The highest astaxanthin production (6170 μg L−1) was obtained at 22.5 g L−1 of reducing sugars. The addition of yeast extract to the yuca medium at concentrations of 0.5–3.0 g L−1 inhibited astaxanthin synthesis. The yuca medium supported a higher production of astaxanthin, 2.5-fold more than that observed
in the YM medium. Journal of Industrial Microbiology & Biotechnology (2000) 24, 187–190.
Received 14 July 1999/ Accepted in revised form 02 December 1999 相似文献
4.
Extracellular human granulocyte-macrophage colony stimulating factor (hGM-CSF) expression was studied under the control of
the GAP promoter in recombinant Pichia pastoris in a series of continuous culture runs (dilution rates from 0.025 to 0.2 h−1). The inlet feed concentration was also varied and the steady state biomass concentration increased proportionally demonstrating
efficient substrate utilization and constancy of the biomass yield coefficient (Yx/s) for a given dilution rate. The specific product formation rate (qP) showed a strong correlation with dilution rates demonstrating growth associated product formation of hGM-CSF. The volumetric
product concentration achieved at the highest feed concentration (4×) and a dilution rate of 0.2 h−1 was 82 mg l−1 which was 5-fold higher compared to the continuous culture run with 1× feed concentration at the lowest dilution rate thus
translating to a 40 fold increase in the volumetric productivity. The specific product yield (YP/X) increased slightly from 2 to 2.5 mg g−1, with increasing dilution rates, while it remained fairly invariant, for all feed concentrations demonstrating negligible
product degradation or feed back inhibition. The robust nature of this expression system would make it easily amenable to
scale up for industrial production. 相似文献
5.
The effects of salinity on cell growth and docosahexaenoic acid (DHA) content of three marine microalgal strains, Crythecodinium cohnii ATCC 30556, C. cohnii ATCC 50051 and C. cohnii RJH were investigated. The lag phases of the three strains increased with increasing salinity in Porphyridium medium. The
specific growth rate of C. cohnii ATCC 30556 was the highest at 9 g L−1 NaCl while the other two strains had their highest specific growth rates at 5 g L−1 NaCl. The highest cell dry weight concentrations of 2.51 g L−1 and 1.56 g L−1 were achieved at 9 g L−1 NaCl for C. cohnii ATCC 30556 and ATCC 50051, respectively, while the highest dry weight concentration of 2.49 g L−1 was achieved at 5 g L−1 NaCl for C. cohnii RJH. The highest cell growth yield coefficient on glucose was 0.5 g g−1 for both C. cohnii ATCC 30556 and C. cohnii RJH and 0.45 g g−1 for C. cohnii ATCC 50051. All three strains responded to the change of salinity by modifying their cellular fatty acid compositions. At
9 g L−1 NaCl, C. cohnii ATCC 30556 had the highest total fatty acid content and DHA (C22:6) proportion. In contrast, C. cohnii ATCC 50051 and C. cohnii RJH had the highest DHA content at 5 g L−1 NaCl. C. cohnii ATCC 30556 and ATCC 50051 had the highest DHA yield (131.55 and 68.24 mg L−1 respectively) at 9 g L−1 NaCl while C. cohnii RJH had the highest DHA yield (128.83 mg L−1) at 5 g L−1 NaCl.
Received 27 May 1999/ Accepted in revised form 27 August 1999 相似文献
6.
A locally isolated Chlorococcum sp. could accumulate astaxanthin and its esters as secondary carotenoids. The secondary carotenoids
could reach a concentration of 5.2 mg g−1 d. wt, and were located in the cytoplasm and chloroplast as globules. Cells grew best at pH 8.0 and 30 °C, at which the growth
rate was about 0.066 h−1. Acidic condition (pH 5.5 and 6.5) and slightly elevated temperature (35 °C) enhanced the cellular accumulation of astaxanthin.
Outdoor studies indicated that Chlorococcum sp. grew well in a tubular photobioreactor. In medium containing 2 mM and 10 mM
NH4CI, the cellular contents of total secondary carotenoids and astaxanthin reached similar levels (5.0 mg g−1 d. wt and 2.0 mg g−1 d. wt, respectively) in the 15 days of cultivation, while the yield of total secondary carotenoids and astaxanthin in 10
mM NH4CI were higher (45 mg L−1 and 18 mg L−1, respectively). The advantages of tolerance to high temperature and extreme pH values, relative fast growth rate and ease
of cultivation in outdoor system suggest that Chlorococcum sp. could be a potential candidate for mass production of secondary
carotenoids in particular astaxanthin.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
7.
Analysis and optimization of a two-substrate fermentation for xylitol production using Candida tropicalis 总被引:1,自引:0,他引:1
Xylitol, a functional sweetener, was produced from xylose using Candida tropicalisATCC 13803. A two-substrate fermentation was designed in order to increase xylitol yield and volumetric productivity. Glucose
was used initially for cell growth followed by conversion of xylose to xylitol without cell growth and by-product formation
after complete depletion of glucose. High glucose concentrations increased volumetric productivity by reducing conversion
time due to high cell mass, but also led to production of ethanol, which, in turn, inhibited cell growth and xylitol production.
Computer simulation was undertaken to optimize an initial glucose concentration using kinetic equations describing rates of
cell growth and xylose bioconversion as a function of ethanol concentration. Kinetic constants involved in the equations were
estimated from the experimental results. Glucose at 32 g L−1 was estimated to be an optimum initial glucose concentration with a final xylose concentration of 86 g L−1 and a volumetric productivity of 5.15 g-xylitol L−1 h−1. The two-substrate fermentation was performed under optimum conditions to verify the computer simulation results. The experimental
results were in good agreement with the predicted values of simulation with a xylitol yield of 0.81 g-xylitol g-xylose−1 and a volumetric productivity of 5.06 g-xylitol L−1 h−1.
Received 16 June 1998/ Accepted in revised form 28 February 1999 相似文献
8.
Phycocyanin production by high cell density cultivation of Spirulina platensis in batch and fed-batch modes in 3.7-L bioreactors with a programmed stepwise increase in light intensity program was investigated.
The results showed that the cell density in fed-batch culture (10.2 g L−1) was 4.29-fold that in batch culture (2.38 g L−1), and the total phycocyanin production in the fed-batch culture (0.795 g L−1) was 3.05-fold that in the batch culture (0.261 g L−1). An unstructured kinetic model to describe the microalga culture system including cell growth, phycocyanin formation, as
well as glucose consumption was proposed. The data fitted the models well (r
2 > 0.99). Furthermore, based on the kinetic models, the potential effects of light limitation and photoinhibition on cell
growth and phycocyanin formation can be examined in depth. The models demonstrated that the optimal light intensity for mixotrophic
growth of Spirulina platensis in batch or fed-batch cultures using a 3.7-L bioreactor was 80160 μE m−2 s−1, and the stepwise increase in light intensity can be replaced by a constant light intensity mode.
Received 28 July 1998/ Accepted in revised form 8 October 1998 相似文献
9.
The ferrous iron oxidation kinetics of Thiobacillus ferrooxidans in batch cultures was examined, using on-line off-gas analyses to measure the oxygen and carbon dioxide consumption rates
continuously. A cell suspension from continuous cultures at steady state was used as the inoculum. It was observed that a
dynamic phase occurred in the initial phase of the experiment. In this phase the bacterial ferrous iron oxidation and growth
were uncoupled. After about 16 h the bacteria were adapted and achieved a pseudo-steady state, in which the specific growth
rate and oxygen consumption rate were coupled and their relationship was described by the Pirt equation. In pseudo-steady
state, the growth and oxidation kinetics were accurately described by the rate equation for competitive product inhibition.
Bacterial substrate consumption is regarded as the primary process, which is described by the equation for competitive product
inhibition. Subsequently the kinetic equation for the specific growth rate, μ, is derived by applying the Pirt equation for bacterial substrate consumption and growth. The maximum specific growth rate,
μ
max, measured in the batch culture agrees with the dilution rate at which washout occurs in continuous cultures. The maximum
oxygen consumption rate, q
O2,max, of the cell suspension in the batch culture was determined by respiration measurements in a biological oxygen monitor at
excess ferrous iron, and showed changes of up to 20% during the course of the experiment. The kinetic constants determined
in the batch culture slightly differ from those in continuous cultures, such that, at equal ferric to ferrous iron concentration
ratios, biomass-specific rates are up to 1.3 times higher in continuous cultures.
Received: 8 February 1999 / Accepted: 17 February 1999 相似文献
10.
The growth behavior of Clostridium thermobutyricum JW171K and its production of butyric acid were investigated under continuous cultivation in a recently developed rotary fermentor.
Using low dilution rates (up to 40 times the shortest doubling time), the continuous culture conditions caused metabolic shifts
from butyrate formation to the production of acetate. Using an 18-h volumetric retention time, no true steady state in butyrate
formation was achieved after 22 days, although the optical density was stable. Acetate and butyrate were formed in an oscillatory
mode with an alternating predominance between these two products, indicating an oscillation between the less exergonic acetate-forming
but higher ATP (4ATP mol−1 glucose) forming mode, and the more exergonic butyrate and 3ATP mol−1 glucose forming mode. During the continuous culture drastic changes in cell morphology occurred and, at the lower dilution
rates, long, granulose-containing, filamentous cells with rounded protuberances and swellings were observed. A maximal butyrate
concentration of 18.4 g L−1 and a productivity of about 2.4 g L−1 per h (at 25–27 mM concentration in the broth) were obtained. Journal of Industrial Microbiology & Biotechnology (2000) 24, 7–13.
Received 26 April 1999/ Accepted in revised form 16 August 1999 相似文献
11.
Acetobacter aceti have been grown on ethanol under inhibitory conditions created by high concentrations of phenol. A defined medium with no
vitamin or amino acid supplements has been used such that ethanol was the sole carbon substrate. The culture temperature was
maintained at 30 °C while the pH was manually controlled to fall within the range 4.5–6.0 during ethanol consumption. Growth
on ethanol at a few thousand milligrams per litre (below the known inhibitory level) resulted in a maximum specific growth
rate of 0.16 h−1 with a 95% yield of acetic acid, followed immediately by acetic acid consumption at a growth rate of 0.037 h−1. Phenol was found to inhibit growth by decreasing both the specific growth rate and the biomass yield during ethanol consumption.
On the other hand, the yield of acetic acid during ethanol consumption and the yield of biomass during acetic acid consumption
remained constant, independent of phenol inhibition. A model is presented and is shown to represent the phenol-inhibited growth
behaviour of A. aceti during both ethanol and acetic acid consumption.
Received: 6 November 1998 / Received revision: 8 February 1999 / Accepted: 12 February 1999 相似文献
12.
A Pessoa Jr I M de Mancilha S Sato 《Journal of industrial microbiology & biotechnology》1997,18(6):360-363
Sugar cane bagasse hemicellulosic fraction submitted to hydrolytic treatment with 100 mg of sulfuric acid per gram of dry
mass, at 140°C for 20 min, was employed as a substrate for microbial protein production. Among the 22 species of microorganisms
evaluated, Candida tropicalis IZ 1824 showed TRS consumption rate of 89.8%, net cell mass of 11.8 g L−1 and yield coefficient (Yx/s) of 0.50 g g−1. The hydrolyzate supplemented with rice bran (20.0 g L−1), P2O5 (2.0 g L−1) and urea (2.0 g L−1) provided a TRS consumption rate of 86.3% and a cell mass of 8.4 g L−1. At pH 4.0 cellular metabolism was inhibited, whereas at pH 6.0 the highest yield was obtained. The presence of furfural
(2.0 g L−1) hydroxymethylfurfural (0.08 g L−1) and acetic acid (3.7 g L−1) in the hydrolyzate did not interfere with cultivation at pH 6.0.
Received 25 October 1996/ Accepted in revised form 10 March 1997 相似文献
13.
The esterification reaction between stearic acid and lactic acid using Rhizomucor miehei lipase and porcine pancreas lipase was optimized for maximum esterification using response surface methodology. The formation
of the ester was found to depend on three parameters namely enzyme/substrate ratio, lactic acid (stearic acid) concentration
and incubation period. The maximum esterification predicted by theoretical equations for both lipases matched well with the
observed experimental values. In the case of R. miehei lipase, stearoyl lactic acid ester formation was found to increase with incubation period and lactic acid (stearic acid)
concentrations with maximum esterification of 26.9% at an enzyme/substrate (E/S) ratio of 125 g mol−1. In the case of porcine pancreas lipase, esterification showed a steady increase with increase in incubation period and lactic
acid (stearic acid) concentration independent of the E/S ratios employed. In the case of PPL, a maximum esterification of
18.9% was observed at an E/S ratio of 25 g mol−1 at a lactic acid (stearic acid) concentration of 0.09 M after an incubation period of 72 h.
Received: 12 February 1999 / Received revision: 31 May 1999 / Accepted: 4 June 1999 相似文献
14.
The carotenoid composition of the astaxanthin-producing green alga Chlorella zofingiensis was investigated using high-performance liquid chromatography. Astaxanthin, adonixanthin, and zeaxanthin are the major carotenoids
in this alga. The pigment pattern was characterized during the accumulation period, and in response to diphenylamine (DPA),
an inhibitor of carotenoid biosynthesis. An increase in zeaxanthin followed by a decrease in xanthophyll was seen after the
induction of astaxanthin biosynthesis by glucose. This biphasic kinetics of zeaxanthin was parallel to the marked increase
in adonixanthin (from 0 mg g−1 to 0.21 mg g−1) and astaxanthin (from 0.05 mg g−1 to 0.35 mg g−1) and decrease of β-carotene (from 0.30 mg g−1 to 0.03 mg g−1). More importantly, unlike the Haematococcus alga, in which there was a high β-carotene accumulation after DPA treatment, C. zofingiensis showed an accumulation of extra zeaxanthin instead of β-carotene after treatment of the cells with DPA. All these results
observed in vivo studies corroborate the observations in vitro studies at the enzyme level that zeaxanthin is a substrate
for the carotenoid oxygenase in C. zofingiensis. It is suggested that zeaxanthin might be an important intermediate and not an end product of the biosynthetic pathway of
astaxanthin. Therefore, a new pathway for astaxanthin formation by C. zofingiensis, which is different from that of the other astaxanthin-producing microorganisms, is proposed. An understanding of the astaxanthin
biosynthetic pathway may yield important information toward the optimization of astaxanthin production, especially for the
improvement of astaxanthin through genetic manipulations. 相似文献
15.
Beauvericin (BEA) is a cyclic hexadepsipeptide mycotoxin with notable phytotoxic and insecticidal activities. Fusarium redolens Dzf2 is a highly BEA-producing fungus isolated from a medicinal plant. The aim of the current study was to develop a simple
and valid kinetic model for F. redolens Dzf2 mycelial growth and the optimal fed-batch operation for efficient BEA production. A modified Monod model with substrate
(glucose) and product (BEA) inhibition was constructed based on the culture characteristics of F. redolens Dzf2 mycelia in a liquid medium. Model parameters were derived by simulation of the experimental data from batch culture.
The model fitted closely with the experimental data over 20–50 g l−1 glucose concentration range in batch fermentation. The kinetic model together with the stoichiometric relationships for biomass,
substrate and product was applied to predict the optimal feeding scheme for fed-batch fermentation, leading to 54% higher
BEA yield (299 mg l−1) than in the batch culture (194 mg l−1). The modified Monod model incorporating substrate and product inhibition was proven adequate for describing the growth kinetics
of F. redolens Dzf2 mycelial culture at suitable but not excessive initial glucose levels in batch and fed-batch cultures. 相似文献
16.
The freshwater microalga Chlorella vulgaris was grown heterotrophically in fed-batch 50–600-L fermenters at 36°C, on aerated and mixed nutrient solution with urea as
a nitrogen and glucose as a carbon and energy source. Cell density increased from the initial value 6.25 to 117.18 g DW L−1 in 32 h in the fermenter 50 L at a mean growth rate 3.52 g DW L−1 h−1. The DW increase in the fermenter 200 L was from 7.25 to 94.82 g DW L−1 in 26.5 h at a mean growth rate 3.37 g DW L−1 h−1. Mean specific growth rate μ was about 0.1 h−1 in the both fermenters, if nutrients and oxygen were adequately supplied. The DW increase in the fermenter 600 L was from
0.8 to 81.6 g DW L−1 in 66.5 h at a mean growth rate 1.22 g DW L−1 h−1 and μ = 0.07 h−1. A limitation of the cell growth rate in 600 L fermenter caused by a low dissolved oxygen concentration above cell densities
higher than 10 g DW L−1) occurred. Specific growth rate decreased approximately linearly with increasing glucose concentration (25–80 g glucose L−1) at the beginning of cultivation and decreased with the time of cultivation. The cell yield was 0.55–0.69 g DW (g glucose)−1. The content of proteins, β-carotene, and chlorophylls in the cells steadily increased and starch content decreased, by keeping
aerated and mixed culture another 12 h in fermenter after the cell growth was stopped due to glucose deficiency. 相似文献
17.
Jasna Hrenovic Tomislav Ivankovic Lavoslav Sekovanic Mirela Rozic 《Central European Journal of Biology》2008,3(2):143-148
The antibacterial effect of cationic surfactants against the pure culture of phosphate (P)-accumulating bacterium Acinetobacter junii was investigated. The estimated EC50 values of the N-dodecylpyridinium chloride (DPC) for growth inhibition was 1.4±0.5 × 10−6 mol L−1 and for the inhibition of the P-uptake rates 7.3±2.6 × 10−5 mol L−1. The estimated EC50 values of the N-cetylpyridinium chloride (CPC) for growth inhibition was 4.9±1.3 × 10−7 mol L−1 and for the inhibition of the P-uptake rates 7.7±2.9 × 10−6 mol L−1. This suggests the importance of controlling the amounts of cationic surfactants in influent of the wastewater treatment
systems in order to avoid the possible failure of the biological P removal from wastewaters. 相似文献
18.
Chun Fang Shen Taira Kiyota Barbara Jardin Yasuo Konishi Amine Kamen 《Cytotechnology》2007,54(1):25-34
Yeastolate is effective in promoting growth of insect cell and enhancing production of recombinant protein, thus it is a key
component in formulating serum-free medium for insect cell culture. However, yeastolate is a complex mixture and identification
of the constituents responsible for cell growth promotion has not yet been achieved. This study used sequential ethanol precipitation
to fractionate yeastolate ultrafiltrate (YUF) into six fractions (F1–F6). Fractions were characterized and evaluated for their
growth promoting activities. Fraction F1 was obtained by 65% ethanol precipitation. When supplemented to IPL-41 medium at
a concentration of 1 g L−1, fraction F1 showed 71% Sf-9 cell growth improvement and 22% β-galactosidase production enhancement over YUF (at 1 g L−1 in IPL-41 medium). However, the superiority of F1 over YUF on promoting cell growth gradually diminished as its concentration
in IPL-41 medium increased. At 4 g L−1, the relative activity of F1 was 93% whereas YUF was 100% at the same concentration. At 1 g L−1, four other fractions (F2–F5) precipitated with higher ethanol concentrations and F6, the final supernatant, showed growth
promoting activities ranging from 32 to 80% as compared to YUF (100%). Interestingly, a synergistic effect on promoting cell
growth was observed when F6 was supplemented in IPL-41 medium in presence of high concentrations of F1 (>3 g L−1). The results suggest that ethanol precipitation was a practical method to fractionate growth-promoting components from YUF,
but more than one components contributed to the optimum growth of Sf-9 cells. Further fractionation, isolation and identification
of individual active components would be needed to better understand the role of these components on the cell metabolism. 相似文献
19.
J. Carlos Roseiro P. J. Partidário N. Lobo M. J. Marçal 《Applied microbiology and biotechnology》1999,52(4):546-552
The change of dilution rate (D) on both Methylophilus methylotrophus NCIMB11348 and Methylobacterium sp. RXM CCMI908 growing in trimethylamine (TMA) chemostat cultures was studied in order to assess their ability to remove
odours in fish processing plants. M. methylotrophus NCIMB11348 was grown at dilution rates of 0.012–0.084 h−1 and the biomass level slightly increased up to values of D around 0.07 h−1. The maximum cell production rate was obtained at 0.07 h−1 corresponding to a maximum conversion of carbon into cell mass (35%). The highest rate of TMA consumption was 3.04 mM h−1 occurring at D=0.076 h−1. Methylobacterium sp. RXM CCMI908 was grown under similar conditions. The biomass increased in a more steep manner up to values of D around 0.06 h−1. The maximum cell production rate (0.058 g l−1h−1) was obtained in the region close to 0.06 h−1 where a maximum conversion of the carbon into cell mass (40%) was observed. The maximum TMA consumption was 2.33 mM h−1 at D=0.075 h−1. The flux of carbon from TMA towards cell synthesis and carbon dioxide in both strains indicates that the cell is not excreting
products but directing most of the carbon source to growth. Carbon recovery levels of approximately 100% show that the cultures
are carbon-limited. Values for theoretical maximum yields and maintenance coefficients are presented along with a kinetic
assessment based on the determination of the substrate saturation constant and maximum growth rate for each organism.
Received: 25 February 1999 / Received revision: 14 May 1999 / Accepted: 17 May 1999 相似文献
20.
Influence of culture conditions such as light, temperature and C/N ratio was studied on growth of Haematococcus pluvialis and astaxanthin production. Light had significant effect on astaxanthin production and it varied with its intensity and direction
of illumination and effective culture ratio (ECR, volume of culture medium/volume of flask). A 6-fold increase in astaxanthin
production (37 mg/L) was achieved with 5.1468·107 erg·m−2·s−1 light intensity (high light, HL) at effective culture ratio of 0.13 compared to that at 0.52 ECR, while the difference in
the astaxanthin production was less than 2 — fold between the effective culture ratios at 1.6175·107 erg·m−2·s−1 light intensity (low light, LL). Multidirectional (three-directional) light illumination considerably enhanced the astaxanthin
production (4-fold) compared to unidirectional illumination. Cell count was high at low temperature (25 °C) while astaxanthin
content was high at 35 °C in both autotrophic and heterotrophic media. In a heterotrophic medium at low C/N ratio H. pluvialis growth was higher with prolonged vegetative phase, while high C/N ratio favoured early encystment and higher astaxanthin
formation. 相似文献