Effect of light intensity on beta-carotene production and extraction by Dunaliella salina in two-phase bioreactors.
ABSTRACT Application of two-phase bioreactors is a useful technique for improvement of the productivity of fermentations. Fermentative extraction of the products in situ is performed in this technique. The effect of light intensity on the extraction of beta-carotene from Dunaliella salina, in the fermentative extraction, has been investigated. Three different average light exposures were applied: 1.5 x 10(-8) (low), 2.7 x 10(-8) (intermediate) and 4.5 x 10(-8) (high) micromol s(-1) per cell. Results show that beta-carotene content of the cells increases by increasing the light exposure. Increase in the beta-carotene content of the cells is not necessarily coupled with an increase in the volumetric production of beta-carotene. Final volumetric production is about the same for the three bioreactors. beta-Carotene extraction rate is enhanced by the increase in the light exposure. The results suggest that extraction rate is related to beta-carotene content of the cells and is not essentially related to the volumetric production of beta-carotene. Although the effectiveness of extraction with respect to the light input is comparable for all light intensities applied, increasing the light input per cell leads to a higher volumetric extraction rate. Moreover, extracted beta-carotene stays very pure even so the extraction increased by the increase of light intensity.
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ABSTRACT: Carotenoids are widely used in nutraceutical, additives and cosmetics as colorants and antioxidants. Dunaliella is the main natural source which accumulates massive amount of carotenoids. This study examines the effect of different concentrations of NaCl (0.3M to 2M) and light intensities of 50 and 150 µmol/m²s on total carotenoids accumulated by Dunaliella tertiolecta (DCCBC26), from Urmia lake (North West of Iran) compared to those obtained from Dunaliella salina CCAP 19/18 and also the wild type Dunaliella salina WT strains. In all microalgaes production of carotenoids were triggered by increase in light intensities. Changes of intensity from 50 µmol/m²s to 150 µmol/m²s led to 2.4, 2.1 and 1.4 folds of carotenoids production by D. salina CCAP, D. salina WT and D. tertiolecta respectively. In both salina strains carotenoids production improved with higher salinity picking at salt concentration of 2M, while D. tertiolecta showed optimum carotenoids production at 0.7M. INTRODUCTION Carotenoids are chemicals with significant commercial interest which are used as coloring agents in neutraceuticals, pharmaceuticals, cosmetics and foods (1). These compounds have antioxidant properties and have attracted attention as potential agents in chemoprevention of cancers (2). They have beneficial role as dietaries in cataract and also in age-related macular degeneration (3). Of about 1000 carotenoids found in nature only a few of them occur in abundance in fruits and vegetables. These include β-carotene (carrots), lycopene (tomatoes) and lutein (spinach) (4). Although some carotenoids e.g. β-carotene and zeaxanthin are available in synthetic forms, there is growing interest on natural microalgal as well as bacterial and yeast sources of carotenoids driven by the world public opinion on synthetic additives (5). Recently bacteria have been investigated for possible accumulation of carotenoids. The nonfastidious and nonpathogenic Flavobacterium multivorum have been considered as an important microbial source for production of zeaxanthin (5,6,7). Rhodotorula glutinis and Phafia rhodozyma are among yeasts with capabilities of carotenoid accumulation (8,9). Microalgae are eucaryotic photosynthetic microorganisms which are used to produce highly valuable compounds such as carotenoids (10). Increasing attention in recent years has been paid to Dunaliella a microalgae of which Dunaliella bardawil and D. salina have shown potential sources for large amounts of β-carotene and glycerol (11,12). The halotolerant green algae are able to grow in a wide salt range of 50 mM to 5.5 M (close to the saturation limit of NaCl). Although high salinity favours carotenoid production by the microalgae but cell density is usually depressed at elevated salt concentrations (12,13). Carotenoid production and accumulation are reported to be positively affected by white-light irradiation in algae, fungi, and bacteria. However one should not expect a unique response of organsisms to illumination. It is also well documented that extent of carotenoid production by cells of microalgae is influenced by light densities and increasing photon flux densities result in higher carotenoids accumulation (14). The present study aimed to clarify the significance of salt and light intensity on carotenoids accumulation by a Dunaliella tertiolecta isolated from the salty Urmia Lake in North-west of Iran compared to those by two strains of Dunaliella salina (CCAP 19/18 and WT).04/2012; 14.
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ABSTRACT: β-carotene is the main source of pro-vitamin A and is widely used as a food colorant, with a global market estimated to surpass USD 280 million in 2015. The majority of the β-carotene commercialized in the world is obtained by chemical synthesis from β-ionone. Alternatively, the production of β-carotene can be reached on a biotechnological basis, using filamentous fungi, bacteria, microalgae, and yeasts as producers, or even by extraction from vegetable sources, such as oil palm (Elaeis guineensis) and buriti (Mauritia vinifera). The present review is focused on the current technologies for β-carotene production and presents an overview of new tendencies regarding the carotenoids extraction from microbial and vegetal feedstocks, as well as processes for their concentration. Keywordsβ-carotene– Dunaliella –Palm– Blakeslea –Enzyme extractionFood and Bioprocess Technology 04/2012; 4(5):693-701. · 4.12 Impact Factor
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ABSTRACT: Multicellular organisms can be regenerated from totipotent differentiated somatic cell or nuclear founders [1-3]. Organisms regenerated from clonally related isogenic founders might a priori have been expected to be phenotypically invariant. However, clonal regenerant animals display variant phenotypes caused by defective epigenetic reprogramming of gene expression , and clonal regenerant plants exhibit poorly understood heritable phenotypic ("somaclonal") variation [4-7]. Here we show that somaclonal variation in regenerant Arabidopsis lineages is associated with genome-wide elevation in DNA sequence mutation rate. We also show that regenerant mutations comprise a distinctive molecular spectrum of base substitutions, insertions, and deletions that probably results from decreased DNA repair fidelity. Finally, we show that while regenerant base substitutions are a likely major genetic cause of the somaclonal variation of regenerant Arabidopsis lineages, transposon movement is unlikely to contribute substantially to that variation. We conclude that the phenotypic variation of regenerant plants, unlike that of regenerant animals, is substantially due to DNA sequence mutation.Current biology: CB 08/2011; 21(16):1385-90. · 10.99 Impact Factor