Eleonora Sforza

University of Padova | UNIPD · Department of Industrial Engineering

Two diazotrophic cyanobacteria (Anabaena cylindrica PCC 7122 and Nostoc sp. PCC 7120) were cultivated to produce cyanophycin, a nitrogen reserve compound, under nitrogen fixing conditions. In preliminary continuous experiments, Nostoc sp. was shown to be more efficient, accumulating a higher amount of cyanophycin and showing a greater capability to...

The production of cyanophycin by photosynthetic microorganisms, as a high-value bio-based compound, is getting increasing interest. The aim of this work is to maximize the production of this compound by the cyanobacterium Synechocystis sp. in semi-batch cultivation systems, by applying a data-driven modeling approach based on the Design of Dynamic...

The application of microalgae to wastewater treatment is an emerging technology following a circular economy approach. The optimization of such a process for large-scale applications in continuous reactors is not trivial, since both high nutrients removal and biomass productivity are desired. As microalgae are able to change their composition as a...

In 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 obli...

Glyphosate will be banned from Europe by the end of 2022, but its widespread use in the last decades and its persistence in the environment require the development of novel remediation processes. In this work, a bacterial consortium was designed de novo with the aim to remove glyphosate from polluted water, supported by the oxygen produced by a mic...

Flashing light is a promising strategy to increase light penetration in microalgal cultures, even though its actual advantage is still a matter of discussion, in particular in batch cultures. In this work, we demonstrated that the cultivation of Arthrospira maxima in steady-state continuous photobioreactors under high frequencies (up to 3700 Hz) of...

To disclose the net effect of light on microalgal growth in photobioreactors, self-shading and mixing-induced light–dark cycles must be minimized and discerned from the transient phenomena of acclimation. In this work, we performed experiments of continuous microalgal cultivation in small-scale photobioreactors with different thicknesses (from 2 to...

Cyanophycin is a molecule produced by cyanobacteria under stressful conditions, and used as a renewable biodegradable feedstock in various industrial applications. A correlation between the amount of cyanophycin in the biomass and the internal cell phosphorus reserve has been demonstrated for Synechocystis sp. PCC 6803. Here, a mathematical model b...

The integration of semi‐transparent photovoltaics (PVs) with photobioreactors (PBRs) is a promising strategy to increase photoconversion efficiency, ensuring simultaneous electricity and algal biomass production. In this study, Arthrospira maxima is cultivated in an integrated system with a dye‐sensitized solar module (DSSM) to the front of the PBR...

Cyanophycin, an intracellular reserve molecule synthetized by cyanobacteria, is considered as a potential biobased raw material for the industrial sector. It is usually produced through the cultivation of photosynthetic microorganisms in batch systems, which are affected by the high variability of cyanophycin accumulation due to varying growth phas...

Irradiation with light emitting diodes (LEDs) is proposed as a method to increase the photoconversion efficiency in large-scale microalgal cultivation. Although several authors have reported the possibility of using colored LEDs in batch systems and for many species, the overall energy efficiency of a continuous system integrated with fine-tuned LE...

Microscale photobioreactors for microalgae growth represent an interesting technology for fast data production and biomass characterization; however, the small scale poses severe monitoring challenges, as traditional methods cannot be used. Non-invasive techniques are therefore needed to quantify biomass concentration and other culture properties,...

There 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 m...

Protein-rich spent yeast is a waste by-product of brewing and other fermentation industry. A continuous-flow hydrothermal treatment called ‘flash hydrolysis’ was deployed for protein recovery and yeast disposal. A feed slurry with 1-15 wt% yeast was hydrolyzed at temperatures ranging between 160-280 °C for a very short residence time of 10±2 s. Usi...

Metabolically engineered cyanobacteria are promising photosynthetic cell factories to produce valuable compounds in view of a bio-based industry. However, when the producer population is affected by a production burden, it usually experiences genetic instability leading to cells that lose the production capability, here defined as retro-mutants, wh...

Tubular photobioreactors (PBRs) guarantee high microalgal productivities but suffer from oxygen accumulation. It is known that the tube length must be limited to prevent build-up of high oxygen levels, but the combined effect of other variables (light intensity and biomass concentration) was not fully addressed. In this work, a mathematical model i...

The application of microalgae in wastewater treatment is gaining increasing attention due to the possible environmental benefits of using photosynthetic organisms for bioremediation. Tannery wastewaters, however, may be inhibiting for microorganisms’ growth due to the presence of toxic compounds, especially chromium. In this work, we assessed the p...

Microalgae cultivation has been the object of relevant interest for many industrial applications. Where high purity of the biomass/product is required, closed photobioreactors (PBRs) appear to be the best technological solution. However, as well as cost, the major drawback of closed systems is oxygen accumulation, which is well known to be responsi...

Photorespirometry is a quick method to assess the effect of several variables on algal growth performances in complex media such as wastewater. In this work, respirometry was applied to derive kinetic parameters of nitrogen exploitation. Oxygen production was found to be related to the internal nitrogen quota, suggesting that the Droop model is mor...

In this study, the feasibility of integrating microalgae cultivation in a biogas production process that treats the organic fraction of municipal solid waste (OFMSW) was investigated. In particular, the biomass growth performances in the liquid fraction of the digestate, characterized by high ammonia concentrations and turbidity, were assessed toge...

The use of phototrophic organisms in wastewater treatment is gaining increasing interest, due to the possibility of exploiting photosynthetic oxygenation, thus lowering treatment costs and environmental impacts. Mixed consortia of phototrophic organisms and aerobic bacteria rapidly develop in photobioreactors receiving wastewaters; in this case, th...

In conventional continuous bioreactor operations, it is a common practice to decouple the hydraulic retention time (HRT) from the solid retention time (SRT). When dealing with photosynthetic microorganisms, light intensity plays a major role in the growth kinetics; thus, the effect of HRT and SRT on biomass productivity may differ from that in chem...

Microalgae are receiving increasing attention as potential sources of high-value compounds. In particular fucoxanthin, a carotenoid pigment produced by some microalgae and diatoms has been shown to exhibit a range of promising health benefits [1]. Fucoxanthin content is influenced by several variables, firstly light. A few works aimed at evaluating...

Synechocystis 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 h...

Modeling the growth of photosynthetic organisms is challenging, due to the complex role of light, which can be limiting because of self-shading, or photoinhibiting in the case of high intensities. A case of particular interest is represented by nitrogen-fixing cyanobacteria, whose growth is controlled not only by the light intensity, but also by th...

Modeling microalgal mixotrophy is challenging, as the regulation of algal metabolism is affected by many environmental factors. A reliable tool to simulate microalgal behavior in complex systems, such as wastewaters, may help in setting the proper values of operative variables, provided that model parameters have been properly evaluated. In this wo...

Microalgal-bacteria consortia application on wastewater treatment has been widely studied, but a deeper comprehension of consortium interactions is still lacking. In particular, mixotrophic exploitation of organic compounds by microalgae affects gas (CO2 and O2) exchange between microalgae and bacteria, but it is not clear how environmental conditi...

Microalgae-bacteria consortia application to wastewater treatment is considered as a potential and cheap strategy towards a self-sustaining oxygen-carbon dioxide gas exchange. However, microalgae can also carry out mixotrophy, thus reducing the net oxygen production, due to consumption of organic substrates. In this work, respirometric tests were u...

The exploitation of symbiotic interactions between species-specific algae-bacteria consortia is a viable strategy to improve wastewater remediation efficiency. In this work, specific interactions between Chlorella protothecoides and Brevundimonas diminuta were exploited to improve nutrient removal. The beneficial effects of the presence of B. dimin...

Nannochloropsis is commonly recognized as a valuable biomass source for the production of both biofuels and high value nutraceuticals compounds. Phosphorus is one of the main nutrients affecting microalgal growth and composition. In this work, the effect of using higher P concentrations in cultivation of Nannochloropsis salina was studied showing a...

The 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/...

Nutrient recycling is of paramount importance for microalgal cultivation aimed at biofuels production. Though different techniques have been assessed at lab-scale level, less information is available on the actual nutrient recovery yields and on the energy balance of a large-scale closed-loop process. In this work two technologies, namely anaerobic...

In this work, the effect of nitrogen limitation on Tetradesmus (Scenedesmus) obliquus cultivation was evaluated in a continuous system operated at steady-state to assess the carbohydrate productivity in a single step. Under continuous irradiance (150 and 650 μmol photons m−2 s−1), with an optimized nitrogen limitation in the reactor inlet stream, a...

Cyanobacterium aponinum is a thermotolerant cyanobacterium species isolated from different thermal springs and showing potential therapeutic application thanks to the synthesis and release of exopolysaccharides with anti-inflammatory and immunomodulating properties. This work investigates the effects of temperature and light on growth rate, biomass...

Microalgal industrial production requires high surface area, resulting in production costs currently unacceptable. A possible optimization of land use for the cultivation of Scenedesmus obliquus is proposed, by conjoint production of biomass and electricity using photovoltaic cells (PV). For this purpose, biomass cultivation in a continuously opera...

Carbohydrate cultivation optimization from microalgae and cyanobacteria.

Nowadays, the production of carbohydrates or lipids from microalgae with good productivities values is limited because, generally, the systems used are in batch mode operation, with two steps of nutrient starvation (mainly, nitrogen) after cultivation. In this work, a literature outlook and a comparison of the results obtained in continuous mode wi...

Outdoor industrial-scale microalgae cultivation is limited by several factors, among which a low efficiency of overall light energy conversion plays a key role, mainly due to photosaturation and photoinhibition under high irradiations. This work aims at improving the overall photoconversion efficiency in a microalgal production photobioreactor (PBR...

Synechococcus PCC 7002 is an interesting species in view of industrial production of carbohydrates. The cultivation performances of this species are strongly affected by the pH of the medium, which also influences the carbohydrate accumulation. In this work, different methods of pH control were analyzed, in order to obtain a higher production of bo...

Nutrient recycling is essential to make microalgae cultivation sustainable at industrial scale. To this aim, lab-scale anaerobic digestion experiments of Chlorella vulgaris after lipid extraction were carried out to evaluate biogas yield and nutrients recovery in the liquid digestate. Then, this liquid fraction was used as source of nutrients for c...

Supplementary Information

The cost-effective production of liquid biofuels from microalgae is limited by several factors such as recovery of the lipid fractions as well as nutrients management. Flash hydrolysis (FH), a rapid hydrothermal process, has been successfully applied to fractionate the microalgal biomass into solid biofuels intermediates while recovering a large am...

Chlorella vulgaris is commonly recognized as an interesting species for bioethanol production due to its carbohydrate content. Carbohydrates accumulation is often obtained under nitrogen starvation, which on the other hand may lead to a reduced biomass production. In this work, the effect of nitrogen limitation in a continuous system was assessed,...

Supplementary File

Microalgae and cyanobacteria have attracted much attention for developing new biofuels production technologies. In particular, cyanobacteria seem to be promising in view of third generation bioethanol production. The most used source of inorganic carbon for algal cultivation is concentrated CO2 in air. However the use of this source can account of...

The production of biofuels from microalgae is associated with high demands of nutrients (nitrogen and phosphorus) required for growth. Recycling nutrients from the residual biomass is essential to obtain a sustainable production. In this work, the aqueous phase obtained from flash hydrolysis of Scenedesmus sp. was used as cultivation medium for a m...

The growth of Scenedesmus obliquus in photobioreactors was both experimentally investigated and numerically simulated by solving a population balance equation (PBE), accounting for cell growth and division. The PBE is solved using the Finite size domain Complete set of trial functions Method Of Moments (FCMOM) and a wide range of operative conditio...

Maximizing biomass productivity and photosynthetic efficiency are key factors to develop large-scale microalgae cultivation for biodiesel production. If the photobioreactor (PBR) is not operated under proper conditions, productivity and efficiency values drop considerably. In this work, the growth of Scenedesmus obliquus in continuous flat-panel PB...

In this work, Nannochloropsis salina was cultivated in a continuous-flow flat-plate photobioreactor, working at different residence times and irradiations to study the effect of the specific light supply rate on biomass productivity and photosynthetic efficiency. Changes in residence times lead to different steady-state cell concentrations and spec...

Most relevant factors influencing microalgae growth are light availability and utilization. In view of maximizing the photosynthetic efficiency of a photobioreactor, the evaluation of maintenance energy is essential to understand the energy requirement for cell growth and it is also a key parameter of most mathematical growth models. In this work,...

One of the main limitations to large-scale production of biofuels derived from microalge is the lower efficiency of sunlight conversion. The maximum theoretical value for photosynthetic efficiency is hardly achieved in real outdoor cultivation systems, mainly due to inefficient light utilization, in addition to photosaturation and photoinhibition p...

Microalgae provide one of the more promising strategies for the production of renewable biodiesel and liquid fuels. Coupling biodiesel production and wastewater treatment based on the use of microalgae can be an effective approach for achieving sustainable production. Several pilot programs aimed at lipid production are currently working with Acuto...

Increasing concern over climate change and the impact of greenhouse gas emissions as well as diminishing global oil reserves has pushed research into alternative energy sources. Among these options, reducing the cost of microalgae cultivation, a promising source for renewable energy, is a key step in commercializing biodiesel production. Microalgae...

The use of bicarbonate as carbon supply in a large scale photobioreactor for industrial microalgae production could reduce the compression and transportation costs associated with the direct use of CO 2 from flue gas. Some microalgae species are able to directly exploit bicarbonate as a carbon source, but the actual yield in view of large scale pro...

The industrial production of microalgae in continuous photobioreactors (PBRs) was investigated using an integrated experimental-modeling approach. A lab-scale PBR was assembled for microalgae cultivation, in the shape of thin-layer flat-vertical panels of 250 mL, in order to minimize the effect of cell self-shading and optimize the light use. Two m...

The exploitation of microalgae in a wastewater treatment process is currently an open issue, and its actual applicability is still under investigation. In this work the effects of temperature, day/night irradiation and bacterial competition were studied on growth and nutrient removal of Chlorella protothecoides cultivated in real and unsterilized p...

In view of an efficient industrial autotrophic cultivation of microalgal biomass, the role of light into photobioreactor is still to be fully ascertained. The influence of different light intensities was investigated using both continuous illumination and alternation of light and dark cycles with different frequencies, which mimic illumination vari...

In the last years new renewable energy sources started to be exploited to compensate exhausting fossil fuels and minimize anthropogenic factors on climate change. Microalgae have reemerged as potential next-generation feedstock for biofuels and they are considered very promising on the long term, since they have a potentially high productivity per...

Despite the high potential as feedstock for the production of fuels and chemicals, the industrial cultivation of microalgae still exhibits many issues. Yield in microalgae cultivation systems is limited by the solar energy that can be harvested. The availability of reliable models representing key phenomena affecting algae growth may help designing...

In this work, the production of Scenedesmus obliquus in a continuous flat-plate laboratory-scale photobioreactor (PBR) under alternated day-night cycles was tested both experimentally and theoretically. Variation of light intensity according to the four seasons of the year were simulated experimentally by a tunable LED lamp, and effects on microalg...

One of the main parameters influencing microalgae production is light, which provides energy to support metabolism but, if present in excess, can lead to oxidative stress and growth inhibition. In this work, the influence of illumination on Scenedesmus obliquus growth was assessed by cultivating cells at different light intensities in a flat plate...

The capability to grow microalgae in nonsterilized wastewater is essential for an application of this technology in an actual industrial process. Batch experiments were carried out with the species in nonsterilized urban wastewater from local treatment plants to measure both the algal growth and the nutrient consumption. Chlorella protothecoides sh...

This work presents the results of a thorough EROEI (Energy Return on Energy Investment) analysis for biocrude production from microalgae processes. We have investigated different alternatives to maximize the energy recoveries of each process considered, which has been modeled and simulated by Aspen PIus (TM). The estimates for feeds and recirculati...

This paper reports new experimental data of microalgae growth and lipid production under autotrophic conditions for the species Nannochloropsis salina. The effect of relevant operating variables is addressed and discussed, and some suggestions to better understand the process behavior are given with respect to lipid content maximization, carbon dio...

Biofuels from algae are highly interesting as renewable energy sources to replace, at least partially, fossil fuels, but great research efforts are still needed to optimize growth parameters to develop competitive large-scale cultivation systems. One factor with a seminal influence on productivity is light availability. Light energy fully supports...

Scheme of the Flat Bed Photobioreactor. The flat-plate photobioreactors were built with transparent materials (polycarbonate) for maximum utilization of light energy. The working volume is 150 ml and the culture is mixed by an air-CO2 flow from a sparger placed in the bottom of the panel. The amount of CO2 in air is regulated by two flow meters. Th...