Search Results (124)

In accordance with growing environmental pressures and the demand for sustainable industrial practices, membrane technologies have emerged as key enablers for increasing efficiency, reducing emissions, and supporting circular processes across multiple sectors. This review focuses on the integration among microalgae-based systems, offering innovative and sustainable solutions for biomass production, carbon capture, and industrial wastewater treatment. In cultivation, membrane photobioreactors (MPBRs) have demonstrated biomass productivity up to nine times greater than that of conventional systems and significant reductions in water (above 75%) and energy (approximately 0.75 kWh/m³) footprints. For carbon capture, hollow fiber membranes and hybrid configurations increase CO₂ transfer rates by up to 300%, achieving utilization efficiencies above 85%. Coupling membrane systems with industrial effluents has enabled nutrient removal efficiencies of up to 97% for nitrogen and 93% for phosphorus, contributing to environmental remediation and resource recovery. This review also highlights recent innovations, such as self-forming dynamic membranes, magnetically induced vibration systems, antifouling surface modifications, and advanced control strategies that optimize process performance and energy use. These advancements position membrane-based microalgae systems as promising platforms for carbon-neutral biorefineries and sustainable industrial operations, particularly in the oil and gas, mining, and environmental technology sectors, which are aligned with global climate goals and the UN Sustainable Development Goals (SDGs). Full article

The sustainable and economically viable production of microalgae biomass for biofuels and high-value bioproducts is highly dependent on precise, multi-parametric monitoring of cultivation systems. This review provides a comprehensive overview of current approaches and technological advances in multi-sensor systems applied to photobioreactors, including flow cytometry, IR spectroscopy, RGB sensors, in situ microscopy, and software-based sensors. The integration of artificial intelligence (AI), the Internet of Things (IoT) and metaheuristic algorithms into monitoring systems is also discussed as a promising way to optimise key ecological, physicochemical, and biological parameters in real time. The report highlights critical factors that influence biomass growth and product yield, such as nutrient concentrations, light intensity, CO₂ levels, pH and temperature. In addition, current technological limitations are highlighted, and future strategies for improving monitoring accuracy, automating cultivation, and improving the biosynthesis of metabolites are outlined. Through a synthesis of the literature and technological trends, this work contributes to the development of smart photobioreactor systems and provides actionable insights to improve large-scale, highly efficient microalgae cultivation in energy and environmental biotechnology. Full article

In this work, the ability of the photosynthetic purple non-sulfur bacterium Rhodopseudomonas sp. to produce H₂ was investigated in two cylindrical photobioreactors (PBRs). The PBRs used in this work had different working volumes: 0.2 L of working volume (named 0.2-PBR) and 4.0 L of working volume (named 4.0-PBR). Two mixing methods were tested in the 4.0-PBR. The first used a rotor with four paddles, and the second a spiral rotor. Additionally, light conversion efficiency (LCE) was assessed for the three conditions tested. The culture in the 0.2-PBR produced 142.15 mL of H₂ with an average H₂ production rate of 0.74 mL/h, an average productivity of 3.70 mL/L/h and an LCE = 0.59%. The culture in the 4.0-PBR produced a total of 806.05 mL and 1642 mL of H₂ with the paddle rotor and the spiral rotor, respectively. The average H₂ production rate and LCE of the two rotors were 2.29 mL/h and LCE = 0.58% in the case of the paddle rotor and 2.87 mL/h and LCE = 0.72% in the case of the spiral rotor. The more uniform and thus more efficient mixing of the cells achieved with the spiral rotor played an important role compared to the paddle rotor, resulting in a higher LCE. This study presents a scale-up from 0.2 L to 4.0 L of the photofermentation process using the purple non-sulfur bacterium Rhodopseudomonas sp. S16-VOGS3. Full article

Monitoring algal growth rates and estimating microalgae concentration in photobioreactor systems are critical for optimizing production efficiency. Traditional methods—such as microscopy, fluorescence, flow cytometry, spectroscopy, and macroscopic approaches—while accurate, are often costly, time-consuming, labor-intensive, and susceptible to contamination or production interference. To overcome these limitations, this study proposes an automated, real-time, and cost-effective solution by integrating machine learning with image-based analysis. We evaluated the performance of Decision Trees (DTS), Random Forests (RF), Gradient Boosting Machines (GBM), and K-Nearest Neighbors (k-NN) algorithms using RGB color histograms extracted from images of Scenedesmus dimorphus cultures. Ground truth data were obtained via manual cell enumeration under a microscope and dry biomass measurements. Among the models tested, DTS achieved the highest accuracy for cell count prediction (R² = 0.77), while RF demonstrated superior performance for dry biomass estimation (R² = 0.66). Compared to conventional methods, the proposed ML-based approach offers a low-cost, non-invasive, and scalable alternative that significantly reduces manual effort and response time. These findings highlight the potential of machine learning–driven imaging systems for continuous, real-time monitoring in industrial-scale microalgae cultivation. Full article

Towards the bioremediation of toxic compounds from aquatic environments using living microalgae, Chlorella vulgaris has emerged as a promising candidate for the removal of heavy metals. The present study advances the scale-up of the microalga’s culture and investigates its efficiency in multi-metal removal (Cu, Cd, Ni, Pb, and Zn at 1 ppm each). Two aeration conditions were investigated: standard/conventional aeration (SA), and an innovative, custom-built micro-bubble aeration (MBA), which optimizes CO₂ residence time to enhance photosynthesis. Conducted in a pilot-scale 30 L photobioreactor (PBR) over a cultivation period of 7 days, control and multi-metal treated cultures were monitored for pH, cell population growth, and pigment content. Heavy metal removal efficiency was evaluated by means of atomic absorption spectroscopy (AAS) on Days 3 and 7 of cultivation. The comparative results reveal that MBA significantly enhances both the population and the photosynthetic pigment content of the cultures. Furthermore, the heavy metal removal efficiency under MBA reached up to 95% even by Day 3 of cultivation, remarkably higher than the 67% of the SA treated culture. These findings not only demonstrate Chlorella vulgaris’s effectiveness in multi-metal treated systems but also highlight the potential of advanced aeration systems to enhance bioremediation efficiency in larger-scale aquatic environments. Full article

This review systematically examines the critical mechanisms and process optimization strategies of algal–bacterial granular sludge (ABGS) technology in wastewater treatment. The key findings highlight the following: (1) enhanced pollutant removal—ABGS achieves >90% COD removal, >80% total nitrogen elimination via nitrification–denitrification coupling, and 70–95% phosphorus uptake through polyphosphate-accumulating organisms (PAOs), with simultaneous adsorption of heavy metals (e.g., Cu²⁺, Pb²⁺) via EPS binding; (2) energy-saving advantages—microalgal oxygen production reduces aeration energy consumption by 30–50% compared to conventional activated sludge, while the granular stability maintains >85% biomass retention under hydraulic shocks; (3) AI-driven optimization—machine learning models enable real-time prediction of nutrient removal efficiency (±5% error) by correlating microbial composition (e.g., Nitrosomonas abundance) with operational parameters (DO: 2–4 mg/L, pH: 7.5–8.5). This review further identifies EPS-mediated microbial co-aggregation and Chlorella–Pseudomonas cross-feeding as pivotal for system resilience. These advances position ABGS as a sustainable solution for low-carbon wastewater treatment, although challenges persist in scaling photobioreactors and maintaining symbiosis under fluctuating industrial loads. Full article

Microalgae are an effective solution for the treatment and valorization of wastewater generated in hydroponic systems. In the current context of sustainability and resource management, the search for ecological alternatives in agriculture is essential. This study investigated the use of wastewater from hydroponic systems, purified by microalgae, for the irrigation of Pelargonium × hortorum. An experiment was designed under controlled conditions in which different irrigation treatments were applied. Hydroponic leachates treated by microalgae were used at 100%, 75%, and 50% (diluted using tap water), in addition to tap water as a negative control and nutrient solution as a positive control. The treatment system was established in a raceway photobioreactor, which allowed the proliferation of microalgae that act as bioremediators for the elimination of pollutants and the removal of nitrogen and phosphorus. The growth parameters, biomass, and general health of the Pelargonium × hortorum plants were evaluated, complemented with physicochemical analyses of the water carried out during the experimental period. These analyses showed that the water obtained after the purification process retained nutrients that can be reused for irrigation. The results indicated that plants irrigated with treated water showed significant improvements in height, diameter, number of leaves, leaf area, leaf dry weight, and flower dry weight compared to those irrigated with tap water. In conclusion, the study shows that the treatment of hydroponic wastewater by means of microalgal cultivation represents a viable and ecological alternative for the irrigation of ornamental plants such as Pelargonium × hortorum. The implementation of this system contributes both to the reduction of pollutants and to the optimal use of water resources, establishing a solid basis for future research in which additional nutrients could be incorporated to balance the nutrient solution studied. Full article

This study showcases an attached-biomass system based on twin-layer technology for cultivating Galdieria phlegrea using municipal wastewater, equipped with a smart sensor system for the remote monitoring of operational parameters. From an industrial scale-up perspective, the system offers high scalability, with low impact and operating costs. Mathematical approximation modelling identified the optimal growth conditions across five experiments. The theoretical yield was estimated to reach 1 kg_DW/m² of biomass within two months. Integrated use of isotopic mass spectrometry and spectrophotometric methods allowed us to study the metabolic strategies implemented by the algal community during the best growth condition at different resolutions, showing an increase in the nitrogen concentration over time and a favourable affinity of the organism for nitrogen species that are commonly present in the urban effluent. SEM studies showed a clean algal biofilm (free of foreign organisms), which could guarantee usage in the high economic potential market of biorefineries. Full article

This study investigated nutrient removal in tubular photobioreactors (PBR) illuminated by Light-Emitting Diodes (LEDs), treating the effluent from an Up-Flow Anaerobic Sludge Blanket (UASB) system followed by a Biological Percolator Filter (BPF). Designed as a tertiary treatment step, the PBRs aimed to minimize eutrophication while promoting microalgal growth through CO₂ assimilation released by bacterial activity—resulting in biomass with potential for value-added applications. The objective of this study was to elucidate the mechanisms responsible for nitrogen and phosphorus removal under a controlled environment. A key novelty of this work lies in the comparative evaluation of red and blue LED illumination in the pilot-scale PBRs used for wastewater treatment. All systems achieved >99% ammoniacal nitrogen removal, while soluble phosphorus removal achieved up to 95%. The highest nitrogen removal rate was observed under red light (10.60 mg L⁻¹ d⁻¹), although there was no difference for blue light, while blue light was more effective for phosphorus removal (3.28 mg L⁻¹ d⁻¹). Assimilation was the primary removal mechanism, supported by microalgae–bacteria interactions and artificial CO₂ injection. The research highlights distinct advantages of each light illumination: the blue-light photobioreactor was more suitable for tertiary treatment, whereas the red-light system showed potential for microalgal biomass-based co-product generation. Full article

Chromochloris zofingiensis is a green alga that serves as a valuable source of lipids, proteins, and carotenoids. Compared to well-studied microalgal carotenoid producers, C. zofingiensis offers several advantages, including high biomass, lipid and carotenoid productivity as well as less susceptibility to contaminations. C. zofingiensis can achieve growth rates up to four times higher than those of H. pluvialis under optimal phototrophic conditions. Although several studies have examined its cultivation and carotenogenesis under different tropic growth modes at laboratory scale, few have focused on pilot-scale systems. The goal of this study is to investigate the microalga’s physiological adaptation in a 200 L tubular photobioreactor during a three-phase semi-continuous cultivation strategy, particularly focusing on the changes in macromolecular and pigment composition. After an initial biomass accumulation phase, a two-phased stress phase was applied combining nutrient depletion (phase 1) and osmotic salt stress conditions (phase 2). Following this procedure, the cellular protein content dropped to 44.7% of its initial level, while the lipid content rose by up to 320%. Additionally, the astaxanthin concentration increased from 1.1 mg/g_DW to 4.9 mg/g_DW during the last osmotic stress phases, aligning with results from published laboratory-scale studies. Full article

The utilization of photosynthetic microbes, such as cyanobacteria and microalgae, offers sustainable solutions to addressing global resource shortages and pollution. While these microorganisms have demonstrated significant potential in biomanufacturing, their industrial application is limited by suboptimal photosynthetic efficiency. Synthetic biology integrates molecular biology, systems biology, and engineering principles to provide a powerful tool for elucidating photosynthetic mechanisms and rationally optimizing photosynthetic platforms. This review summarizes recent advancements in regulating photosynthesis in cyanobacteria and microalgae via synthetic biology, focusing on strategies to enhance light energy absorption, optimize electron transport chains, and improve carbon assimilation. Furthermore, we discuss key challenges in translating these genetic modifications to large-scale bioproduction, highlighting specific bottlenecks in strain stability, metabolic burden, and process scalability. Finally, we propose potential solutions, such as AI-assisted metabolic engineering, synthetic microbial consortia, and next-generation photobioreactor designs, to overcome these limitations. Overall, while synthetic biology holds great promise for enhancing photosynthetic efficiency in cyanobacteria and microalgae, further research is needed to refine genetic strategies and develop scalable production systems. Full article

Microalgae are small, single-celled, or simple multicellular organisms that contain Chlorophyll a, allowing them to efficiently convert CO₂ and water into organic matter through photosynthesis. They are valuable in producing a range of products such as biofuels, food, pharmaceuticals, and cosmetics, making them economically and environmentally significant. Currently, CO₂ is delivered to microalgae cultivation systems mainly through aeration with CO₂-enriched gases. However, this method demonstrates limited CO₂ absorption efficiency (13–20%), which reduces carbon utilization effectiveness and significantly increases carbon-source expenditure. To overcome these challenges, innovative CO₂ supplementation technologies have been introduced, raising CO₂ utilization rates to over 50%, accelerating microalgae growth, and reducing cultivation costs. This review first categorizes CO₂ supplementation technologies used in photobioreactor systems, focusing on different mechanisms for enhancing CO₂ mass transfer. It then evaluates the effectiveness of these technologies and explores their potential for scaling up. Among these strategies, membrane-based CO₂ delivery systems and the incorporation of CO₂ absorption enhancers have shown the highest efficiency in boosting CO₂ mass transfer and microalgae productivity. Future efforts should focus on integrating these methods into large-scale photobioreactor systems to optimize cost-effective, sustainable production. Full article

Microalgae possess the remarkable ability to autotrophically grow, utilizing atmospheric carbon dioxide (CO₂) for photosynthesis, thereby converting solar energy into chemical energy and releasing oxygen. This capacity makes them an effective tool for mitigating industrial CO₂ emissions. Mathematical models are crucial for predicting microalgal growth kinetics and thus assessing their potential as industrial CO₂ sequestration agents under controlled conditions. This study innovatively evaluated the effect of continuously supplying CO₂ from winemaking processes on microalgal cultivation and biomass production, demonstrating a novel approach to both carbon capture and the valorization of a valuable by-product. To analyze microalgal growth kinetics, three mathematical models were employed: Logistic, First Order Plus Dead Time, and Second Order Plus Dead Time. Optimal parameter values for each model were identified using a hybrid search algorithm developed by our research group. First, an integrated microvinification system was established, utilizing two microalgae species, Chlorella spp. (FAUBA-17) and Desmodesmus spinosus (FAUBA-4), in conjunction with yeast fermenters. This system facilitated a comparison of the biomass kinetics of these two microalgae species, selecting Chlorella spp. (FAUBA-17) as the most suitable candidate for subsequent cultivation. A pilot-scale vertical column photobioreactor was then constructed and installed at the Casimiro Wines boutique winery in Angaco, San Juan, Argentina. After 15 days of operation within the photobioreactor, a biomass growth of 1.04 ± 0.05 g/L and 1.07 ± 0.1 g/L was obtained in Photobioreactors 1 and 2, respectively. This novel integrated approach to CO₂ capture in the winemaking process is unprecedented. These findings highlight the potential for producing high-value microalgal biomass, promoting the establishment of a local biorefinery and fostering a circular economy and sustainable social development. Full article

Microalgae biotechnology has taken the world by storm. However, despite its great potential promise, it still cannot be considered a fully consolidated technology due to a crucial challenge: the low rates of biomass productivity. To overcome this hurdle, photobioreactors have been developed as an innovative solution, promising to increase the efficiency of microalgae cultures by providing optimized conditions. However, the results obtained with these systems do not always meet initial expectations, and their large-scale implementation faces complex technical challenges. In light of this, the present review addresses the main aspects related to the design and engineering of photobioreactors, highlighting their potentialities and limitations in overcoming the critical challenges of microalgal biotechnology. Furthermore, we discuss the current technological readiness level and the commercial readiness index of microalgae-based bioproducts from the perspective of industrial-scale production. Full article

The Artificial Tree project, developed by the authors, presents an innovative approach to urban sustainability by integrating microalgae cultivation systems for CO₂ capture, biomass production, and urban cooling. This study evaluates the project’s feasibility and effectiveness in transforming urban furniture into functional photobioreactors that enhance environmental quality. Inspired by natural aesthetics, the Artificial Tree functions as both a CO₂ sink and a biofertilizer producer. Using Scenedesmus microalgae, the system captures 50 kg of CO₂ annually per unit and generates 28 kg of biomass, which further reduces emissions when utilized as a biofertilizer. To assess its impact, a multi-criteria decision analysis (MCDA) method was employed, considering factors such as CO₂ capture, biomass production, social engagement, visual appeal, and scalability. This methodology incorporated a three-level qualitative scale and criteria tailored to compare similar projects with at least three months of operation and available data on microalgae productivity. Results highlight that the Artificial Tree achieves up to 2.5 times more CO₂ fixation than a mature tree while combining environmental benefits with public engagement. Its modular and aesthetic design supports educational outreach and inspires larger-scale implementation. This project demonstrates significant potential to redefine urban spaces sustainably by seamlessly integrating functionality, artistic expression, and public interaction. Full article