Epilithic biofilm on rocky shores is regulated by physico-chemical and biological factors and is important as a source of food for benthic organisms. The influences of environmental and grazing pressure on spatial variability of biomass of biofilm were evaluated on shores on the north coast of Sao Paulo State (SE Brazil). A general trend of greater abundance of microalgae was observed lower on the shore, but neither of the environmental factors evaluated (wave exposure and shore level) showed consistent effects, and differences were found among specific shores or times (September 2007 and March 2008). The abundance of slow-moving grazers (limpets and littorinids) showed a negative correlation with chlorophyll a concentration on shores. However, experimental exclusion of these grazers failed to show consistent results at small spatial scales. Observations of divergent abundances of the isopod Ligia exotica and biomass of biofilm on isolated boulders on shores led to a short exclusion experiment, where the grazing pressure by L. exotica significantly decreased microalgal biomass. The result suggests that grazing activities of this fast-moving consumer probably mask the influence of slow-moving grazers at small spatial scales, while both have an additive effect at larger scales that masks environmental influences. This is the first evaluation of the impact of the fast-moving herbivore L. exotica on microalgal biomass on rocky shores and opens an interesting discussion about the role of these organisms in subtropical coastal environments.; FAPESP Fundacao de Amparo a Pesquisa do Estado de Sao Paulo[06/00559-4]; FAPESP Fundacao de Amparo a Pesquisa do Estado de Sao Paulo[06/60237-0]
Tese de doutoramento em Biological and Chemical Engineering; This work aimed at the development and optimization of systems and techniques for
microalgae cultivation, in order to make the process economically and environmentally
sustainable. Three different strategies were adopted: i) maximize productivity through
the optimization of culture conditions, ii) maximize productivity and decrease costs by
the use of agro-industrial waste as cultivation medium; iii) development of a new, low
cost and highly productive microalgae cultivation system.
Carbon dioxide (CO2) is the most widely used carbon source for photoautotrophic
growth of microalgae. The rate of CO2 fixation (RCO2) by Chlorella vulgaris was
maximized by defining the values of CO2 concentration in air feed and aeration rate.
The results revealed that the maximum RCO2 (2.22 g L-1 d-1) was obtained using 6.5%
(v/v) CO2 and 0.5 vvm. Although biomass concentration and mass productivity were
affected by growth conditions, no differences were obtained in the biochemical
composition of cells.
The optimization of specific productivity (starch and lipids for the production of
bioethanol and biodiesel, respectively) was performed using strategies of nutrient
limitation. Starch accumulation in C. vulgaris cells was evaluated under different initial
concentrations of urea (nitrogen source) and FeNa-EDTA (iron source) in the medium.
Based on the results...
Anjos, Mariana; Vicente, A. A.; Teixeira, J. A.; Dragone, Giuliano
Publicado em //2014Português
Relevância na Pesquisa
The potential use of microalgal biomass as a feedstock for bioethanol production has attracted great attention in recent years. Bioethanol from microalgae can be produced through two distinct pathways: direct dark fermentation or fermentation of saccharified biomass by yeast. The main objective of this work was to assess the influence of increasing glucose concentration derived from hydrolysed microalgal biomass on bioethanol production. The green microalga C. vulgaris (strain P12) was cultivated at room temperature during 15 days in 15-L flat plate photobioreactors. Illumination was provided by cool white fluorescent lamps at an irradiance level of 300 ?mol photon m?2 s?1 and CO2-enriched air (6.5% v/v CO2) was supplied at an aeration rate of 0.1 vvm. Successive disruption of microalgal cells with 0.5M HCl at 121 ºC for 20 min was performed in order to obtain fermentation media with increasing carbohydrate contents (25, 50 and 75 g/L). Microalgal starch was saccharified into glucose by ?-amylase at 60 ºC for 30 min and amyloglucosidase at 55 ºC for 90 min. Fermentations of microalgal starch hydrolysates by Saccharomyces cerevisiae were carried out at 30 ºC during 48 h. Results showed that bioethanol production was enhanced by using microalgal hydrolysates containing elevated glucose concentration. A maximum ethanol concentration of 28.69 ± 0.68 g/L was achieved at 75 g/L initial glucose. It was concluded that ethanol production can be improved by increasing the glucose content in the fermentation medium...
Cell walls of microalgae are variable and contain non-specific domains where different molecules can bind. The enrichment of microalgal biomass with nutrients through adsorption can be an interesting process for the food and feed industry. In this study, naturally occurring polyphenols ((+)-catechin, ()-epicatechin, quercetin, rutin and xanthohumol) were adsorbed onto nonliving cells of freshwater microalgae Chlorella vulgaris. The essential adsorption parameters such as biomass dose and contact time were examined and the adsorption was quantified with Langmuir, Sips and DubininRadushkevich adsorption isotherms. The evaluation of isotherms proved the highest affinity towards Chlorella vulgaris biomass for xanthohumol and quercetin. The biosorption mechanism of Chlorella vulgaris biomass was well described by a pseudo second order kinetic model, with a high regression coefficient. The polyphenol-enriched microalgal biomass was also evaluated for its antioxidant activity. The highest antioxidant activity was detected in the case of biomass enriched with quercetin (77.5% of decolorized DPPH).
The influence of light intensity upon biomass and fatty acid productivity by the microalga Pavlova lutheri was experimentally studied using a novel device. This device was designed to automatically adjust light intensity in a photobioreactor: it takes on-line measurements of biomass concentration, and was successfully tested to implement a feedback control of light based on the growth rate variation. Using said device, batch and semicontinuous cultures of P. lutheri were maintained at maximum growth rates and biomass productivities – hence avoiding photoinhibition, and consequent waste of radiant energy. Several cultures were run with said device, and their performances were compared with those of control
cultures submitted to constant light intensity; the biomass levels attained, as well as the yields of eicosapentaenoic and docosahexaenoic acids were calculated – and were consistently higher than those of their uncontrolled counterpart.
The communities of benthic microalgae that form dense biofilms at the surface of aquatic sediments, or microphytobenthos, are important primary producers in estuarine intertidal flats and shallow coastal waters. The microalgal biomass present in the photic zone of the sediment is a key parameter for ecological and photophysiological studies on microphytobenthos, and has been routinely estimated using hyperspectral reflectance indices based on the chlorophyll (Chl) a red absorption peak at 675 nm, usually the Normalised Difference Vegetation Index (NDVI). This study reports that red region-based biomass indices measured on microphytobenthos biofilms can be significantly affected by the enrichment of reflected light with solar-induced Chl fluorescence emitted by the microalgae. Chl fluorescence emission peaks at 683 nm, counterbalancing the decrease in reflectance centered at 675 nm, thus causing the underestimation of NDVI. The interference of Chl fluorescence was found to be easily identified by a conspicuous double-peak feature in the 670–700 nm region of the second-derivative reflectance spectra. The fluorescence-induced NDVI underestimation was shown to be most pronounced for high surface biomass levels and low incident solar irradiance. Particular aspects of microphytobenthos biofilms...
Microalgae are an enormous biological resource, representing one of the most promising sources for the
development of new food products and applications. Pea protein/k-carrageenan/starch gels, interesting
vegetarian alternatives to dairy desserts, served as model systems to study the addition of microalgal
biomass, its effect, and subsequent rheological behaviour. Spirulina and Haematococcus gels presented
a markedly different rheological behaviour compared to the control mixed biopolymer gelled system.
The present goal is to clarify how these microalgae affect the gelation and interact with each biopolymer
present in the complex mixed gel system. Hence, the aim of the present work is to study the effect of
Spirulina and Haematococcus microalgal biomass addition on the rheological behaviour of pea protein, k-
carrageenan and starch simple gels, as well as in pea protein/k-carrageenan and pea protein/starch
systems. The gelation process was monitored in-situ through dynamic oscillatory measurements
(temperature, time and frequency sweep tests) for a 24 h maturation period, and rheological results were
supported with uorescence optical microscopy observations. The addition of Spirulina and Haematococcus
to biopolymer gelled systems induced signi cant changes in the gels’ rheological behaviour and
microstructure. In general...
Renewable, sustainable and carbon-neutral energy production is needed to deal with the challenges of growing energy demand and climate change. Hydrogen (H2) is most promising in the succession of fuel evolution, with several technical, socio-economic and environmental benefits to its credit . It is an excellent energy carrier as it has the highest energy content per unit weight/mass of any known fuel (142 kJ/g) and upon oxidation produces only water . H2 is being explored for use in combustion engines and fuel-cell electric vehicles, and it is expected that H2 demand increases significantly in the near and long term . Biological hydrogen production processes are found to be more environmentally friendly and less energy intensive as compared to thermochemical and electrochemical processes . In dark fermentation, carbohydrate-rich substrates can be used to produce bioH2 in a process mediated by hydrogenase enzymes of anaerobic microorganisms. Moreover, residues and byproducts from agricultural and food industries or wastewaters can be used, providing inexpensive energy generation with simultaneous waste treatment . Recently, there has been an increasing interest on using microalgal biomass for biofuels production. Besides oil extraction for biodiesel purposes  or sugar extraction for bioethanol production [5-6]...
This paper presents the life cycle inventory (LCI) of hydrogen production by Clostridium butyricum fermentation of Scenedesmus obliquus hydrolysate. The main purpose of this work was to evaluate the potential of H2 production from microalgal biomass and the respective energy consumption and CO2 emissions in the bioconversion process considering the microalga production, acid hydrolysis of S. obliquus biomass, preparation of the inoculum and culture media, and fermentation. The scale-up to industrial production was not envisaged.
The hydrogen yield obtained in this work was 2.9 ± 0.3 mol H2/mol sugars in S. obliquus hydrolysate. Results show that this process of biological production of hydrogen can achieve 7270 MJ/MJH2 of energy consumption and 670Kg CO2/MJH2. The microalgal culture is the stage responsible for 98% of these total final values due to the use of artificial lighting. All stages and processes with the highest values of energy consumption and CO2 emissions were identified for future energetic and environmental optimisation.
The microalga Nannochloropsis sp. was used in this study, in a biorefinery context, as biomass feedstock for the production of fatty acids for biodiesel, biohydrogen and high added-value compounds. The microalgal biomass, which has a high lipid and pigment content (mainly carotenoids), was submitted to supercritical CO2 extraction. The temperature, pressure and solvent flow-rate were evaluated to check their effect on the extraction yield. The best operational conditions to extract 33 glipids/100 gdry biomass were found to be at 40 °C, 300 bar and a CO2 flow-rate of 0.62 g/min. The effect of adding a co-solvent (ethanol) was also studied. When supercritical CO2 doped with 20% (w/w) ethanol was used, it was possible to extract 45 glipids/100 gdry biomass of lipids and recover 70% of the pigments. Furthermore, the remaining biomass after extraction was effectively used as feedstock to produce biohydrogen through dark fermentation by Enterobacter aerogenes resulting in a hydrogen production yield of 60.6 mL/gdry biomass.
Biofuel production from microalgal biomass could be an alternative solution to conventional biofuels typically dependent on food and high land/water demanding crops. However, the economic and energetic viability of microalgal biofuels is limited by their harvesting processes. The finding of innovative, low cost and efficient harvesting method(s) is imperative. In this study, the Electro-Coagulation (EC) was studied as a process to harvest the marine Nannochloropsis sp. microalga. Several EC operational conditions were studied and the best EC recovery efficiency (>97%) was achieved using a current density of 8.3 mA cm2 for 10 min. The quality of the recovered microalgal biomass was evaluated in terms of total lipids, fatty acid and pigment profile where no significant differences were observed after EC treatment. The energy requirements of the harvesting process were estimated and the combination of EC and centrifugation processes proved to decrease significantly the energy demand when compared with the individual process.
The use microalgae biomass for the production of biofuels has received great attention in the last decades. Microalgae biofuels could be important alternative to conventional biofuels since microalgae could be produced at high rates without the need of neither arable land, potable water or competition with food. However, the high energy intensive harvesting processes are limiting the commercial production of microalgae biofuels. In this study, Electro-Coagulation (EC) was used for harvesting the freshwater microalga Chlorella vulgaris and the marine microalga Nannochloropsis sp. The results show that EC could be an alternative to the conventional harvesting processes since it is efficient and produces good quality biomass with low energy requirements.
Renewable, sustainable and carbon-neutral energy production is needed to deal with the challenges of the currently growing energy demand and deleterious climate changes. Hydrogen (H2) is presently seen as an ideal future energy carrier with technical, socio-economic and environmental benefits. H2 can be produced through biological conversion by photosynthesis, photo-heterotrophic and dark fermentation. The interest in biological hydrogen (bioH2) production has recently increased, as the traditional ways of H2 production are still costly and display a negative environmental impact. The research work on bioH2 production conducted at UB-LNEG targets the use of the most diverse feedstock biomass, process optimization and, whenever possible, integration under an energy-oriented biorefinery pathway. Microalgal biomass and agricultural wastes, such as carob pulp and chestnut shells, are excellent examples of non-food renewable biomass that we have already tested as potential feedstock for bioH2 production.
In order to produce single-cell oil for biodiesel, a yeast and a microalga were, for the first time, grown in two separate reactors connected by their gas-phases, taking advantage of their complementary nutritional metabolisms, i.e., respiration and photosynthesis. The yeast Rhodosporidium toruloides was used for lipid production, originating a carbon dioxideenriched outlet gas stream which in turn was used to stimulate the autotrophic growth of Chlorella protothecoides in a vertical-alveolar-panel (VAP) photobioreactor. The microalgal biomass productivity was 0.015 g L1 h1, and its lipid productivity attained 2.2 mg L1- h1 when aerated with the outlet gas stream from the yeast fermenter. These values represent an increase of 94% and 87%, respectively, as compared to a control culture aerated with air. The CO2 bio-fixed by the microalgal biomass reached an estimated value of 29 mg L1 h1 in the VAP receiving the gas stream from the fermenter, a value 1.9 times higher than that measured in the control VAP.
Concerns about climate changes and global water crisis are increasing, considering the low freshwater resources, pollution, and changes in the hydrological cycle. Therefore, water is a precious scarce resource being crucial to develop wastewater treatment and recovery processes to improve water resources management. On the other hand, the problematic of fossil fuels leads to its replacement by biofuels. Thus there are studies  to combine wastewater treatment with microalgal biomass as 3rd generation biofuel sources. This study pretends to apply the biorefinery concept to an innovative photobioreactor (PBR) to treat wastewater with microalgae and later valorise the biomass by producing biohydrogen. It is intended to reduce CO2, phosphorus, nitrogen, ammonium and other pollutants presents in wastewater, according EC targets, since microalgae consume the nutrients for growth thus removing them from the wastewater. Within the WW-SIP Life project, a new type of PBR for urban waste water treatment plant (UWWTP) effluents has been designed and will be scaled up. The tubular vertical PBR prototype (150 L) placed outdoor has an air compressor to perform agitation, a membrane module to permeate the treated water and a settler to concentrate the biomass. The results will be used to scale up a PBR of 1500 L. The PBR was fed with primary effluent from Águas da Figueira (PT) UWWTP and inoculated with Chlorella vulgaris...
The objective of this study was to extract poly(3-hydroxybutyrate) (PHB) from the microalgal biomass of Spirulina LEB 18 for the development of nanofibers by electrospinning method. Different extraction methods were tested. The maximum yield obtained was 30.1 ± 2%. It was possible to produce nanofibers with diameters between 826 ± 188 nm and 1,675 ± 194 nm. An increase in the nanofiber diameter occurred when a flow rate of 4.8 ?L min-1 and a capillary diameter of 0.90 mm were used. The nanofibers produced had up to 34.4% of biomass additives, i.e., non-PHB materials. This can be advantageous, because it enables the conservation of microalgal biomass compounds with bioactive functions.
Microalgae of numerous heterotrophic genera (obligate or facultative) exhibit considerable metabolic versatility and flexibility but are currently underexploited in the biotechnological manufacturing of known plant-derived compounds, novel high-value biomolecules or enriched biomass. Highly efficient production of microalgal biomass without the need for light is now feasible in inexpensive, well-defined mineral medium, typically supplemented with glucose. Cell densities of more than 100 g?l?1 cell dry weight have been achieved with Chlorella, Crypthecodinium and Galdieria species while controlling the addition of organic sources of carbon and energy in fedbatch mode. The ability of microalgae to adapt their metabolism to varying culture conditions provides opportunities to modify, control and thereby maximise the formation of targeted compounds with non-recombinant microalgae. This review outlines the critical aspects of cultivation technology and current best practices in the heterotrophic high-cell-density cultivation of microalgae. The primary topics include (1) the characteristics of microalgae that make them suitable for heterotrophic cultivation, (2) the appropriate chemical composition of mineral growth media, (3) the different strategies for fedbatch cultivations and (4) the principles behind the customisation of biomass composition. The review confirms that...
Effective optimization of microalgae-to-bioethanol process systems hinges on an in-depth characterization of key process parameters relevant to the overall bioprocess engineering. One of the such important variables is the biomass particle size distribution and the effects on saccharification levels and bioethanol titres. This study examined the effects of three different microalgal biomass particle size ranges, 35??m ? x ? 90??m, 125??m ? x ? 180??m, and 295??m ? x ? 425??m, on the degree of enzymatic hydrolysis and bioethanol production. Two scenarios were investigated: single enzyme hydrolysis (cellulase) and double enzyme hydrolysis (cellulase and cellobiase). The glucose yield from biomass in the smallest particle size range (35??m ? x ? 90??m) was the highest, 134.73?mg glucose/g algae, while the yield from biomass in the larger particle size range (295??m ? x ? 425??m) was 75.45?mg glucose/g algae. A similar trend was observed for bioethanol yield, with the highest yield of 0.47?g EtOH/g glucose obtained from biomass in the smallest particle size range. The results have shown that the microalgal biomass particle size has a significant effect on enzymatic hydrolysis and bioethanol yield.
One of the key issues for successful human space exploration is biomedical life support in hostile space and planetary environments that otherwise cannot sustain life. Bioregenerative life support systems (LSS) are one of the options for atmospheric regeneration. To date, no bioregenerative LSS has shown capability for 100% air regeneration. Nor have these LSS been robust enough to simultaneously provide a regenerable complete food source. In contrast to microalgae, traditional plant approaches, e.g. wheat and lettuce, are lacking essential amino acids, vitamins, and micronutrients. Moreover, the rate of photosynthesis by microalgae significantly exceeds that of high plants. Nevertheless, the employment of microalgae in LSS technology was restricted, until recently, due to high water demands. Also the per person requirement of a 40L volume of microalgae in a photobioreactor, to provide daily O2 production, made an algae-based approach less attractive. By employing a vertically stacked membrane bioreactor, coupled with a solar tracker and photon-delivery system, a lightweight air revitalization system for space based applications, with minimal water requirements, can be developed. Our preliminary estimations suggest that a membrane bioreactor...