1,721,201 research outputs found
Exploiting symbiotic interactions between Chlorella protothecoides and Brevundimonas diminuta for an efficient single-step urban wastewater treatment
No full textThe application of microalgal bacteria consortia to the treatment of wastewater is receiving increasing attention, meeting the demand for new green and efficient technologies for water remediation. The specificity of the consortium, however, may strongly affect the performance of the treatment. In fact, even though a general exploitation of the O2/CO2 exchange between microalgae and bacteria is effective, some specific interactions may increase the pollutant removal. With this aim, the co-cultivation of Chlorella protothecoides and Brevundimonas diminuta was tested, with particular attention to the removal capability of nitrogen, phosphorus and chemical oxygen demand (COD) from wastewater. Batch experiments were carried out both for the consortium and, separately, for the bacteria and microalgae alone, in order to compare their performances. B. diminuta showed a remarkable capability for removing organic substances and transforming organic nitrogen to ammonium. C. protothecoides efficiently removed nitrogen and phosphorus. As the specific growth rates of the two organisms are different, the co-cultivation was also carried out also in a continuous system, and the effect of hydraulic retention time (HRT) on the steady-state biomass concentration and nutrient removal efficiency was verified. Residence time was found as the main operating variable for obtaining a significant reduction of pollutants from wastewater
Effect of residence time in continuous photobioreactor on mass and energy balance of microalgal protein production
No full textThere is increasing interest in new protein sources for the food and feed industry and for the agricultural sector, and microalgae are considered a good alternative, having a high protein content and a well-balanced amino acid profile. However, protein production from microalgae presents several unsolved issues, as the biomass composition changes markedly as a function of cultivation operating conditions. Continuous systems, however, may be properly set to boost the accumulation of protein in the biomass, ensuring stable production. Here, two microalgae and two cyanobacterial species were cultivated in continuous operating photobioreactors (PBR) under nonlimiting nutrient conditions, to study the effects of light intensity and residence time on both biomass and protein productivity at steady state. Although light strongly affected biomass growth inside the PBR, the overall protein pool did not vary in response to irradiance. On the other hand, shorter residence times resulted in protein accumulation of up to 68 % in cyanobacteria, in contrast with green algae, where a minor influence of residence time on biomass composition was observed. Energy balance showed that light conversion to protein decreased with light intensity. Protein content was also related to energy costs for cell maintenance. In conclusion, it is shown that residence time is the key variable to increase protein content and yield of protein production, but its effect depends on the specific species
Diazotrophic Cyanobacteria for Protein Production: Hotorespirometry to Assess the Effect of Light and Temperature
No full textProtein production, thriving on the chemical fixation of nitrogen in fertilizers and intensive use of agricultural and livestock practices, significantly compromises environmental sustainability. The need for alternative food resources to meet the raised demand due to the fast-growing global population has turned pressing. Diazotrophic cyanobacteria, capable of converting atmospheric nitrogen into bioavailable forms, offer promise in sustainable protein production, bypassing traditional inefficiencies. Such microorganisms’ potential might be fully exploited if the production process is well-characterized and controlled. The primary objective of this study is to investigate the specific effects of light and temperature on the growth dynamics of Nostoc PCC 7120 by using photorespirometry. The study aims to retrieve kinetic parameters essential for predictive modeling in industrial applications. The optimal light intensity (376 μmol m-2 s-1) was estimated, as well as the optimal temperature. The latter showed to be dependent on culture conditions: under nitrogen-fixing conditions, it drops from 30 to 27 °C, highlighting temperature-driven effects based on the nitrogen source
An internally LED illuminated photobioreactor to increase energy conversion efficiency: Design and operation
No full textIn this work, a novel internally LED illuminated prototype photobioreactor (IIPBR) was designed, rationalizing the light supply with a hexagonal geometry and matching the light spectrum to the most photosynthetically active wavelengths. The IIPBR was designed and operated to produce the biomass in a continuous mode. In this system, Acutodesmus obliquus was cultivated under different light intensities (100–400 μmol m−2 s−1) and residence times (1–1.9 d). At steady state, a maximum productivity of 40.09 ± 1.99 g m−2 d-1 and a photosynthetic efficiency around 22 % were obtained. The data collected were used to carry out a first evaluation of the costs related to illumination, finding that the correct setting of the operative conditions has a great impact on costs, which span from a minimum of 1.82 up to to 20.63 € kg−1 (with electricity supply rated at autumn–winter 2021). The photoconversion efficiency of the lamps and the plant location play an important role and should be taken into account to increase the economic feasibility of the system proposed, thus enlarging the possible fields final applications of the biomass obtained
Light optimization and management technologies for increasing algal bioreactors efficiency
No full textIllumination in microalgae cultivation is a key factor for the achievement of target biomass productivity, and it is strongly influenced by operating variables of the plant. Traditionally, autotrophic microalgae cultivation at mid to large scale is carried out in outdoor open ponds, exploiting sun radiation. This approach often suffers from low photosynthetic efficiencies and low productivities limiting the spread of the microalgae market, which struggle to develop and to ensure the productivity required by an increasing bio-based industrial demand. This chapter is focused on strategies for managing light utilization and improving efficiency under both natural and artificial light. Outdoor cultivation technologies such as sunlight concentrators, spectral converters, and photovoltaics are discussed, among others. The aim is to avoid excessive stress and culture damages due to peak radiation and simultaneously produce electricity to increase the overall process efficiency. For what concerns the artificial light, the improvement in solid-state lighting technologies, represents an alternative to produce high amount of algae biomass, even though artificial lighting increases both capital and operating costs. The minimization of energy losses is then required to curtail the running costs of the system and can be obtained with two main approaches: focusing on spectral matching between the light source and the microalgae absorption; careful management of the reactor operation. The main outcome is that a low light intensity should be used to increase the energy conversion efficiency, carefully assessing the light compensation point. The use of flashing light also represents a viable approach to be considered
Mixotrophy in Synechocystis sp. for the treatment of wastewater with high nutrient content: effect of CO2 and light
No full textSynechocystis sp. has remarkable mixotrophic capabilities, as well as an efficient exploitation of nitrogen and phosphorus, that may be applied in wastewater treatment based on cyanobacteria. To better investigate the exploitation of algal mixotrophy in bioremediation, this species was used in axenic respirometric tests to ascertain the effect of high light and non limiting CO2 supply on the overall regulation of mixotrophy, resulting in an inhibition of the exploitation of organic carbon. The same species was then cultured in real, unsterilized effluent obtained from the acidogenic fermentation of sludge, which contains a high concentration of nutrients (approximately 600, 90 and 6000 mg L−1 of N, P and COD, respectively) and it is often inhibiting for many microalgal species. On the contrary, Synechocystis sp., showed a remarkable growth and a removal up to 96% of phosphorus, 66% of nitrogen and of 68% of COD in such a complex waste stream
5060. Ghinzoni, Galeazzo Maria Sforza e Luigi XI, dans Archivio storico lombardo, XII (1885), 17-32
No full text5060. Ghinzoni, Galeazzo Maria Sforza e Luigi XI, dans Archivio storico lombardo, XII (1885), 17-32. In: Molinier Auguste. Les Sources de l'histoire de France - Des origines aux guerres d'Italie (1494). V. Introduction générale - Les Valois (suite), Louis XI et Charles VIII (1461-1494) Paris : A. Picard et fils, 1904. pp. 98-99
5060. Ghinzoni, Galeazzo Maria Sforza e Luigi XI, dans Archivio storico lombardo, XII (1885), 17-32
No full text5060. Ghinzoni, Galeazzo Maria Sforza e Luigi XI, dans Archivio storico lombardo, XII (1885), 17-32. In: Molinier Auguste. Les Sources de l'histoire de France - Des origines aux guerres d'Italie (1494). V. Introduction générale - Les Valois (suite), Louis XI et Charles VIII (1461-1494) Paris : A. Picard et fils, 1904. pp. 98-99
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
