Revisión sistemática, clasificación infragenérica y análisis cladístico del género Baccharis L. [Asteraceae, Asterae, Baccharidinae]

Tesis presentada para optar al Grado de Doctor en Ciencias NaturalesFil: Giuliano, Daniel A.. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentin

Light regime characterization in a photobioreactor for cultivation of microalgae with high starch content for bioethanol production

The slow development of microalgal biotechnology is due to the failure in the design of large-scale photobioreactors (PBR) where light energy is efficiently utilized. In this work, both the quality and the amount of light reaching a given point of the PBR were determined and correlated with cell density, light path length and PBR geometry. This was made for two different geometries for the downcomer of an airlift PBR using optical fiber technology that allows obtaining information about quantitative and qualitative aspects of light patterns. This is important since the ability of microalgae to use the energy of photons is different, depending on the wavelength of the radiation. The results show that the circular geometry allows a more efficient light penetration, especially in the locations with a higher radial coordinate (r) when compared to the plane geometry; these observations were confirmed by the occurrence of a higher fraction of illuminated volume of the PBR for this geometry. An equation is proposed to correlate the relative light intensity (RLI) with the penetration distance (Pd), for both geometries and different microalgae cell concentrations. It was shown that the attenuation of light intensity is dependent on its wavelength, cell concentration, geometry of PBR and the penetration distance of light

Third generation biofuels from microalgae

Biofuel production from renewable sources is widely considered to be one of the most sustainable alternatives to petroleum sourced fuels and a viable means for environmental and economic sustainability. Microalgae are currently being promoted as an ideal third generation biofuel feedstock because of their rapid growth rate, CO2 fixation ability and high production capacity of lipids; they also do not compete with food or feed crops, and can be produced on non-arable land. Microalgae have broad bioenergy potential as they can be used to produce liquid transportation and heating fuels, such as biodiesel and bioethanol. In this review we present an overview about microalgae use for biodiesel and bioethanol production, including their cultivation, harvesting, and processing. The most used microalgal species for these purposes as well as the main microalgal cultivation systems (photobioreactors and open ponds) will also be discussed

Optimization of CO2 bio-mitigation by Chlorella vulgaris

Abstract Biofixation of \CO2\ by microalgae has been recognized as an attractive approach to \CO2\ mitigation. The main objective of this work was to maximize the rate of \CO2\ fixation ( R \CO\ 2 ) by the green microalga Chlorella vulgaris \P12\ cultivated photoautotrophically in bubble column photobioreactors under different \CO2\ concentrations (ranging from 2% to 10%) and aeration rates (ranging from 0.1 to 0.7 vvm). Results showed that the maximum R \CO\ 2 (2.22 g L−1 d−1) was obtained by using 6.5% \CO2\ and 0.5 vvm after 7 days of cultivation at 30 °C. Although final biomass concentration and maximum biomass productivity of microalgae were affected by the different cultivation conditions, no significant differences were obtained in the biochemical composition of microalgal cells for the evaluated levels of aeration and CO2. The present study demonstrated that optimization of microalgal cultivation conditions can be considered a useful strategy for maximizing \CO2\ bio-mitigation by C. vulgaris.This study was supported by the grants SFRH/BD/44724/2008 (Bruno Fernandes) and SFRH/BPD/44935/2008 (Giuliano Dragone) from Fundacao para a Ciencia e a Tecnologia (Portugal). The authors also acknowledge the financial support received through the projects INNOVALGAE (FCT PTDC/AAC-AMB/108511/2008) and ALGANOL

Effect of nitrogen limitation on starch accumulation in Chlorella vulgaris

Due to the limited stocks of fossil fuels and the production of greenhouse gas carbon dioxide on their combustion alternative sources of energy are being investigated. Recently, microalgae have received much attention as a renewable energy resource because these photosynthetic microorganisms can convert sunlight, water and CO2 into potential biofuels (1). The microalga Chlorella vulgaris, particularly, has been considered as a potential raw material for bioethanol production because it can accumulates high levels of starch when grown under optimized culture conditions (2). The aim of the present work was to study the effect of nitrogen limitation on starch production by the microalgae C. vulgaris. C. vulgaris CCAP 211/1e (P12 strain) was obtained from the Culture Collection of Algal Laboratory, Institute of Botany, Academy of Sciences of the Czech Republic. The original (nitrogen sufficient) growth medium based on the elementary composition of algal biomass had the following initial composition (mg l−1): 1,100 (NH2) 2CO, 237 KH2PO4, 204 MgSO4∙7H2O, 40 C10H12O8N2NaFe, 88 CaCl2, 0.83 H3BO3, 0.95 CuSO4∙5H2O, 3.3 MnCl2∙4H2O, 0.17 (NH4) 6Mo7O24∙4H2O, 2.7 ZnSO4∙7H2O, 0.6 CoSO4∙7H2O, and 0.014 NH4VO3 in distilled water (3). Nitrogen limited growth medium was formulated by omitting urea from the original growth medium. The microalgae were grown in 1 l Schott flasks with 0.4 l of medium. Cultures were maintained at 30ºC under continuous, cool white fluorescent lamps. Light intensity was approximately 100 mmol m‐2 s‐1 at the surface of the photobioreactors. The concentration of suspended algal biomass was determined by optical density measurement at 700 nm. Starch content in the microalgae was determined colorimetrically by the anthrone reaction. The results showed that starch accumulation in C. vulgaris was strongly related to nitrogen concentration. Under nitrogen limited growth conditions, starch constituted 36% of the algal biomass after 118 h of cultivation, whereas nitrogen sufficient microalgae contained 8% of their dry weight as starch. On the other hand, nitrogen sufficient condition led to an increase in biomass concentration, with the highest biomass concentration of 2.06 g l‐1. It can be concluded that accumulation of starch is enhanced in nitrogen limited cultures of C. vulgaris P12

Mixotrophic cultivation of Chlorella vulgaris using industrial dairy waste as organic carbon source

Growth parameters and biochemical composition of the green microalga Chlorella vulgaris cultivated under different mixotrophic conditions were determined and compared to those obtained from a photoautotrophic control culture. Mixotrophic microalgae showed higher specific growth rate, final biomass concentration and productivities of lipids, starch and proteins than microalgae cultivated under photoautotrophic conditions. Moreover, supplementation of the inorganic culture medium with hydrolyzed cheese whey powder solution led to a significant improvement in microalgal biomass production and carbohydrate utilization when compared with the culture enriched with a mixture of pure glucose and galactose,due to the presence of growth promoting nutrients in cheese whey. Mixotrophic cultivation of C.vulgaris using the main dairy industry by-product could be considered a feasible alternative to reduce the costs of microalgal biomass production, since it does not require the addition of expensive carbohydrates to the culture mediumThis study was supported by the grants SFRH/BD/44724/2008 (Bruno Fernandes) and SFRH/BPD/44935/2008 (Giuliano Dragone) from Fundacao para a Ciencia e a Tecnologia (Portugal). The authors also acknowledge the financial support received through the projects INNOVALGAE (FCT PTDC/AAC-AMB/108511/2008) and ALGANOL

Nutrient limitation as a strategy for increasing starch accumulation in microalgae

Increasing microalgal starch content by nutrient limitation has been regarded as an affordable approach for the production of third generation bioethanol. This work evaluated starch accumulation in Chlorella vulgaris P12 under different initial concentrations of nitrogen (0–2.2 g urea L−1) and iron (0–0.08 g FeNa-EDTA L−1) sources, using a central composite design (CCD) for two factors. The obtained model: Starch content (%) = 8.220 − 16.133X1 + 13.850, relating starch accumulation in microalgae with the coded level for initial urea concentration in the growth medium (X1) presented a good concordance between the predicted and experimental values (R2 = 0.94). Since accumulation of starch occurred at nitrogen depletion conditions under which the cell growth was much slower than that observed during nitrogen supplemented cultivations, a two-stage cultivation process for high starch accumulation (>40%) and cell growth of C. vulgaris was proposed: a first cultivation stage using nitrogen- and iron-supplemented medium (initial urea and FeNa-EDTA concentrations of 1.1 and 0.08 g L−1, respectively), followed by a second cultivation stage in a nitrogen- and iron-free medium. The high starch content obtained suggests C. vulgaris P12 as a very promising feedstock for bioethanol production.This research work was supported by the Grants SFRH/BPD/44935/2008 (Giuliano Dragone) and SFRH/BD/44724/2008 (Bruno Fernandes) from Fundacao para a Ciencia e a Tecnologia (Portugal). The authors also acknowledge the financial support received through the projects INNOVALGAE (FCT PTDC/AAC-AMB/108511/2008) and ALGANOL