Effect of nutrient supply status on biomass composition of eukaryotic green microalgae (original) (raw)
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Heterotrophic growth of microalgae: metabolic aspects
World Journal of Microbiology and Biotechnology, 2014
Microalgae are considered photoautotrophic organisms, however several species have been found living in environments where autotrophic metabolism is not viable. Heterotrophic cultivation, i.e. cell growth and propagation with the use of an external carbon source under dark conditions, can be used to study the metabolic aspects of microalgae that are not strictly related to photoautotrophic growth and to obtain high value products. This manuscript reviews studies related to the metabolic aspects of heterotrophic grow of microalga. From the physiological and metabolic perspective, the screening of microalgal strains in different environments and the development of molecular and metabolic engineering tools, will lead to an increase in the number of known microalgae species that growth under strict heterotrophic conditions and the variety of carbon sources used by these microorganisms.
Trends and novel strategies for enhancing lipid accumulation and quality in microalgae
In order to realize the potential of microalgal biodiesel there is a need for substantial impetus involving interventions to radically improve lipid yields upstream. Nutrient stress and alteration to cultivation conditions are commonly used lipid enhancement strategies in microalgae. The main bottleneck of applying conventional strategies is their scalability as some of these strategies incur additional cost and energy. Novel lipid enhancement strategies have emerged to research forefront to overcome these challenges. In this review, the latest trends in microalgal lipid enhancement strategies, possible solutions and future directions are critically discussed. Advanced strategies such as combined nutrient and cultivation condition stress, microalgae-bacteria interactions, use of phytohormones EDTA and chemical additives, improving light conditions using LED, dyes and paints, and gene expression analysis are described. Molecular approaches such as metabolic and genetic engineering are emerging as the potential lipid enhancing strategies. Recent advancements in gene expression studies, genetic and metabolic engineering have shown promising results in enhancing lipid productivity in microalgae; however environmental risk and long term viability are still major challenges.
Author's personal copy Heterotrophic cultures of microalgae: Metabolism and potential products
This review analyzes the current state of a specific niche of microalgae cultivation; heterotrophic growth in the dark supported by a carbon source replacing the traditional support of light energy. This unique ability of essentially photosynthetic microorganisms is shared by several species of microalgae. Where possible, heterotrophic growth overcomes major limitations of producing useful products from microalgae: dependency on light which significantly complicates the process, increase costs, and reduced production of potentially useful products. As a general role, and in most cases, heterotrophic cultivation is far cheaper, simpler to construct facilities, and easier than autotrophic cultivation to maintain on a large scale. This capacity allows expansion of useful applications from diverse species that is now very limited as a result of elevated costs of autotrophy; consequently, exploitation of microalgae is restricted to small volume of high-value products. Heterotrophic cultivation may allow large volume applications such as waste-water treatment combined, or separated, with production of biofuels. In this review, we present a general perspective of the field, describing the specific cellular metabolisms involved and the best-known examples from the literature and analyze the prospect of potential products from heterotrophic cultures.
Heterotrophic cultures of microalgae: metabolism and potential products
Water research, 2011
This review analyzes the current state of a specific niche of microalgae cultivation; heterotrophic growth in the dark supported by a carbon source replacing the traditional support of light energy. This unique ability of essentially photosynthetic microorganisms is shared by several species of microalgae. Where possible, heterotrophic growth overcomes major limitations of producing useful products from microalgae: dependency on light which significantly complicates the process, increase costs, and reduced production of potentially useful products. As a general role, and in most cases, heterotrophic cultivation is far cheaper, simpler to construct facilities, and easier than autotrophic cultivation to maintain on a large scale. This capacity allows expansion of useful applications from diverse species that is now very limited as a result of elevated costs of autotrophy; consequently, exploitation of microalgae is restricted to small volume of high-value products. Heterotrophic culti...
Oceanological and Hydrobiological Studies, 2018
Screening of fourteen Baltic green algal strains provided basic data on their mass culture potential for the purpose of valuable biomass production with particular emphasis on lipid content. Selected microalgae were grown under non-stressed conditions in order to identify those characterized by efficient lipid production. The tested strains exhibited significant differences in growth patterns and lipid yields. Strains belonging to Chlorella and Stichococcus genera exhibited the highest growth rates, ranging from 0.39 d-1 to 0.50 d-1 and thus the highest final cell density (> 107 cells ml-1). Furthermore, five strains: C. minutissima BA-12, C. fusca BA-18, C. vulgaris BA-80, Monoraphidium sp. BA-165 and Chlorella sp. BA-167 were characterized by distinctively high lipid yield (> 60 mg l-1). The same strains, together with C. vulgaris BA-02, were also shown as those with the highest volumetric lipid productivity, reaching > 30 mg l-1 d-1. The tested Baltic strains performed w...
The right stuff; realizing the potential for enhanced biomass production in microalgae
Frontiers in Energy Research
There is growing evidence that eukaryotic microalgae can become a more sustainable and profitable alternative than terrestrial crops to produce feed, fuels, and valuable coproducts. The major factor driving progress in algal biomass production is the potential of microalgae to produce substantially greater biomass per unit land area than terrestrial crops. To be financially feasible, however, current algal biomass yields must be increased. Given the fact that algal biomass production is in its infancy there exist multiple opportunities to improve biomass yields. For example, recent bioprospecting efforts have led to the identification of new microalgal strains having biomass yields that compete economically with plant biomass. Substantial increases in biomass yields have also been achieved using advanced genetic engineering approaches. Targeted improvements in photosynthetic efficiency have led to three-fold increases in algal biomass yields. One genetic tool that has seen limited a...
Journal of Applied Phycology, 2014
An economically feasible microalgal lipid industry heavily relies on the selection of suitable strains. Because microalgae lipid content increases under a range of adverse conditions (e.g. nutrient deprivation, high light intensity), photosynthetic activity is usually strongly reduced. As a consequence, lipid productivity rapidly declines overtime, after reaching a maximum within the first days of cultivation. The microalgae Chlorella vulgaris, Chlorococcum littorale, Nannochloropsis oculata, Nannochloropsis sp., Neochloris oleoabundans, Stichococcus bacillaris and Tetraselmis suecica were compared on fatty acid content and productivity, and also on photosynthetic activity under nitrogen (N) starvation. Cultures in N-replete conditions were used as reference. Photosystem II (PSII) maximum efficiency was followed during the experiment, as proxy for the change in photosynthetic activity of the cells. Strains with a high capacity for both lipid accumulation as well as high photosynthetic activity under N starvation exhibited a high lipid productivity over time. Among the tested strains, Nannochloropsis sp. showed highest fatty acid content (45 % w/w) and productivity (238 mg L −1 day −1) as well as PSII maximum efficiency, demonstrating to be the most suitable strain, of those tested, for lipid production. This study highlights that for microalgae, maintaining a high photosynthetic efficiency during stress is the key to maintain high fatty acid productivities overtime and should be considered when selecting strains for microalgal lipid production.
Bioprocess engineering of microalgae to optimize lipid production through nutrient management
Microalgae have been used commercially as a feed-stock for the production of high-value compounds, pigments, cosmetics, and nutritional supplements. In addition, because of their rapid growth rates, high photosynthetic efficiency, and high lipid and protein content, commodity products including biodiesel, feed supplements, and polyunsaturated fatty acids derived from algal biomass are of current interest. Since microalgae lack non-photosynthetic structures and float in water , they do not need massive amounts of structural cellulose found in land plants. Thus, under optimal culture conditions, some oleaginous species can allocate up to 70 % of their bio-mass to lipids. Lipid production and its regulation in microalgae are species-specific and influenced by environmental conditions. Various strategies have been developed to improve lipid productivity and fatty acid composition to meet specific production goals. Manipulation of physiochemical parameters, tro-phic modes, and nutrient levels, known as process engineering, is a simple approach that leads to desired alterations in the biochemical composition of algal biomass, including lipid quantity and quality. In this paper, we review the effects of manipulating biochemical parameters such as necessary nutrients (C, N, P, S, Fe, and Si), NaCl concentration, and pH of culture medium to optimize lipid content and profile in some algae strains with commercial potential.
FEMS Microbiology Ecology, 2021
Physiological changes that drive the microalgal–bacterial consortia are poorly understood so far. In the present novel study, we initially assessed five morphologically distinct microalgae for their ability in establishing consortia in Bold's basal medium with a bacterial strain, Variovorax paradoxus IS1, all isolated from wastewaters. Tetradesmus obliquus IS2 and Coelastrella sp. IS3 were further selected for gaining insights into physiological changes, including those of metabolomes in consortia involving V. paradoxus IS1. The distinct parameters investigated were pigments (chlorophyll a, b, and carotenoids), reactive oxygen species (ROS), lipids and metabolites that are implicated in major metabolic pathways. There was a significant increase (>1.2-fold) in pigments, viz., chlorophyll a, b and carotenoids, decrease in ROS and an enhanced lipid yield (>2-fold) in consortia than in individual cultures. In addition, the differential regulation of cellular metabolites such a...