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.
- SourceAvailable from: Peter Lindblad[show abstract] [hide abstract]
ABSTRACT: Full text: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3665214/ Green microalgae for several decades have been produced for commercial exploitation, with applications ranging from health food for human consumption, aquaculture and animal feed, to coloring agents, cosmetics and others. Several products from green algae which are used today consist of secondary metabolites that can be extracted from the algal biomass. The best known examples are the carotenoids astaxanthin and β-carotene, which are used as coloring agents and for health-promoting purposes. Many species of green algae are able to produce valuable metabolites for different uses; examples are antioxidants, several different carotenoids, polyunsaturated fatty acids, vitamins, anticancer and antiviral drugs. In many cases, these substances are secondary metabolites that are produced when the algae are exposed to stress conditions linked to nutrient deprivation, light intensity, temperature, salinity and pH. In other cases, the metabolites have been detected in algae grown under optimal conditions, and little is known about optimization of the production of each product, or the effects of stress conditions on their production. Some green algae have shown the ability to produce significant amounts of hydrogen gas during sulfur deprivation, a process which is currently studied extensively worldwide. At the moment, the majority of research in this field has focused on the model organism, Chlamydomonas reinhardtii, but other species of green algae also have this ability. Currently there is little information available regarding the possibility for producing hydrogen and other valuable metabolites in the same process. This study aims to explore which stress conditions are known to induce the production of different valuable products in comparison to stress reactions leading to hydrogen production. Wild type species of green microalgae with known ability to produce high amounts of certain valuable metabolites are listed and linked to species with ability to produce hydrogen during general anaerobic conditions, and during sulfur deprivation. Species used today for commercial purposes are also described. This information is analyzed in order to form a basis for selection of wild type species for a future multi-step process, where hydrogen production from solar energy is combined with the production of valuable metabolites and other commercial uses of the algal biomass.Critical Reviews in Biotechnology 07/2012; · 5.10 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: To prevent degradation of intracellular retinoids through in situ extraction from the cells, a two-phase culture system was performed. Several organic solvents, including n-alkanes, mineral oils and cosmetic raw materials, were applied as the extraction phase. Of the n-alkanes, n-decane had the highest retinoid production as 134 mg/l after 72 h. For mineral oil, light and heavy mineral oil gave retinoid productions of 158 and 174 mg/l after 96 h, respectively. Of other materials, isopropyl myristate gave the highest retinoid production of 181 mg/l. These results indicate that many types of oils can be applied for retinoid production, and optimization of the in situ extraction process will lead to further improve of economical production for the industrial purpose.Biotechnology Letters 10/2013; · 1.85 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: Over the last decade, the use of microalgae for biofuel production and carbon dioxide sequestration has become a challenge worldwide. Processing costs are still too high for these methods to be profitable though, leading to a need to find high value by-products to optimise the added value of this biomass. For high-throughput screening of such metabolites, it is essential to reach the inner content of the cell. This paper presents research and development of a technique enabling a high extraction yield of any metabolite, taking into account the difficulty of extracting bound and or inaccessible molecules with a wide variety of polarities. To this end, several disruption techniques were tested at laboratory scale on two biological models: Porphyridium purpureum and Phaeodactylum tricornutum. A mixer mill gave the best results, offering access to a broad diversity of metabolites from microalgae for high-throughput screening.Bioresource Technology 08/2012; 124:311-20. · 4.75 Impact Factor