Search Results (181)

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

This study investigates the effects of salinity and pH modulation on the growth, biochemical composition, and bioactive compound production of Limnospira platensis under photoautotrophic batch cultivation. Cultures were grown in cylindrical photobioreactors using modified Jourdan medium, with controlled variations in NaCl concentrations (0.2–10 g L⁻¹) and pH levels (9–11) to simulate moderate environmental stress. Maximum biomass productivity (1.596 g L⁻¹) was achieved at pH 11 with 10 g L⁻¹ NaCl, indicating that L. platensis can tolerate elevated stress conditions. Phycocyanin (PC) content peaked at 9.54 g 100 g⁻¹ dry weight (DW) at pH 10 and 5 g L⁻¹ NaCl, triple the value at pH 9, highlighting optimal physiological conditions for pigment synthesis. Protein fraction dominated biomass composition (40–60%), while total lipid content increased significantly under high pH and salinity. Polyphenol content reached 19.5 mg gallic acid equivalents (GAE) gDW⁻¹ at pH 10 with 0.2 g L⁻¹ NaCl, correlating with the highest antioxidant activity (Trolox equivalent antioxidant capacity). These findings underscore the potential of L. platensis as a valuable source of proteins, pigments, and antioxidants, and emphasize the utility of moderate environmental stress in enhancing biomass quality, defined by protein, pigment, and antioxidant enrichment. While this study focused on physiological responses, future research will apply omics approaches to elucidate stress-response mechanisms. This study provides insights into optimizing cultivation strategies for large-scale production exploitable in food, pharmaceutical, and bio-based industries. Full article

The microalga Tetradesmus obliquus has emerged as a promising candidate for biotechnological and industrial applications due to its rapid growth, resilience under diverse environmental conditions, and potential for bioactive compound production. This study presents a multiparametric characterization of dry T. obliquus biomass cultivated in patented industrial-scale photobioreactors, integrating thermochemical, elemental, antioxidant, and protein analyses. Proximate and ultimate analyses were conducted to assess fuel potential, revealing favorable volatile matter (VM = 64.80–72.44%) and fixed carbon (FC = 15.77–21.23%) contents. The HHV (18.32–22.75 MJ·kg⁻¹) and LHV (16.86–21.24 MJ·kg⁻¹) confirmed the biomass as a viable candidate for solid biofuel. The elemental composition provided the total nitrogen values, subsequently used to estimate the protein content via both the Kjeldahl and Dumas methods, with results ranging from 36.66% to 40.02%, in line with the literature. Despite the absence of detectable antioxidant activity under the tested DPPH conditions, the biomass demonstrated a robust nutritional profile and energy potential. These findings support the industrial relevance of T. obliquus biomass, particularly for applications targeting sustainable protein sources and bioenergy solutions. 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

This study investigated the treatment of unsterilized, undiluted, and unfiltered liquid digestate in a large-scale photobioreactor over a period of 33 weeks using a consortium of microalgae and bacteria. The generated biomass was analyzed for a wide spectrum of value-added compounds. The impact of organic loading rates (OLR) on the microbial culture was determined, and the influence of the biomass storage method on its qualitative composition was also analyzed. The experiment showed optimal growth of microalgae at OLR = 0.1 gCOD/L/day (where COD is Chemical Oxygen Demand), while a higher OLR value led to culture destabilization. Microglena sp., an algae not commonly applied for digestate treatment, showed low tolerance to changes in process conditions (OLR increase) but high readaptation potential when the OLR was lowered to its initial value. Significant changes in the microbial community were observed during the treatment. In Phases 1 and 2, Desmodesmus subspicatus and Actinomycetota phylum dominated in the community, while in Phase 3, Microglena sp. and Firmicutes were the most abundant. Total nitrogen, orthophosphates, and soluble COD were reduced by 89–99%. The biomass storage method had a notable impact on the content of lipids, fatty acids, and pigments. The protein amount was 32.75–33.59% of total solids (TS), while total lipid content was 15.76–19.00% TS, with stearic and palmitic acid being dominant. The effect of the storage regime on the potential biomass valorization was also discussed. Full article

Photosynthetic organisms such as cyanobacteria have the potential for the sustainable production of complex organic molecules due to their ability to use light as an energy source to fix CO₂ and assimilate inorganic nutrients. Over the past decade, large efforts have been put into the metabolic engineering of cyanobacteria to produce various compounds such as alcohols, isoprenoids, biopolymers, and recombinant proteins. Forskolin is a structurally complex labdane-type diterpenoid with eight chiral carbon atoms and is naturally produced in the root cork of the plant Plectranthus barbatus. Forskolin is a potent cAMP activator indicated as a pharmaceutical for a variety of diseases. In the plant, forskolin biosynthesis from geranylgeranyl diphosphate involves six enzymes: two terpene synthases, three cytochrome P450s, and a single acetyltransferase. In this work, we express all six biosynthetic genes from Plectranthus barbatus in Synechocystis sp. PCC. 6803 and demonstrate heterologous production of this complex diterpenoid in a phototroph cyanobacterium. Forskolin titers reached 25.0 ± 4.4 µg/L and the forskolin was entirely secreted into the media. The forskolin-producing Synechocystis strain and empty vector control were cultivated in a photobioreactor for 8 days. Both strains showed similar chlorophyll a contents, and the forskolin-producing strain reached a slightly higher OD₇₃₀ than the control. Forskolin began accumulating in the supernatant after 4 days and increased over time. These results indicate that forskolin production did not negatively impact cell growth. 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

Microalgae are photosynthetic organisms with rapid growth and high biochemical diversity, capable of thriving in a variety of environments. Among them, dinoflagellates, particularly symbiotic species like Durusdinium glynnii, have gained attention due to their potential for biotechnological applications, especially in the production of valuable fatty acids. However, the delicate cultivation of dinoflagellates remains a challenge due to their sensitivity to shear stress and complex morphology. In this study, we evaluated the influence of inoculum percentage (10%, 25%, and 50%) on the growth performance and fatty acid profile of D. glynnii during a scale-up process from test tubes to a pilot-scale photobioreactor. Higher inoculum concentrations (50%) promoted faster acclimatization, higher specific growth rates (µ_max), and greater final biomass densities, optimizing the cultivation process. Meanwhile, lower inoculum concentrations (10%) favored the accumulation of polyunsaturated fatty acids, particularly DHA (C22:6n3), indicating a trade-off between biomass productivity and fatty acid biosynthesis. Overall, D. glynnii demonstrated robust adaptability, reinforcing its potential as a sustainable source of bioactive compounds. Further studies focusing on cellular and metabolic pathways are needed to better elucidate the mechanisms underlying lipid production and growth in this promising species. 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

Marine microalgae from the genus Nannochloropsis are promising candidates for the photoautotrophic production of eicosapentaenoic acid (EPA, C20:5), a polyunsaturated fatty acid known for its numerous health benefits. A recent study demonstrated that Microchloropsis salina can accumulate high amounts of EPA when cultivated in flat-plate gas-lift photobioreactors. This study aimed to characterize an alternative strain, Nannochloropsis oceanica, and compare its biomass and EPA productivity to M. salina. Applying simulated dynamic climate conditions of a repeated sunny summer day in Eastern Australia, N. oceanica was cultivated in LED-illuminated flat-plate gas-lift photobioreactors. The results showed significantly higher biomass growth and EPA contents compared to M. salina. An EPA productivity of 33.0 ± 0.6 mg_EPA L⁻¹ d⁻¹ has been achieved in batch processes with N. oceanica. Scaling up the photoautotrophic process to 8 m² thin-layer cascade photobioreactors resulted in doubled concentrations of N. oceanica biomass compared to laboratory-scale batch processes. This improvement was likely due to the reduced fluid layer depth, which enhanced light availability to the microalgal cells. Using urea instead of nitrate as a nitrogen source further improved the EPA production of N. oceanica in thin-layer cascade photobioreactors, achieving CDW concentrations of up to 17.7 g L⁻¹ and thus a high EPA concentration of 843 mg L⁻¹. These findings highlight N. oceanica as an alternative to M. salina for sustainable EPA production, offering potential for further industrial applications. 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

Interest in microalgae cultivation is continuously growing due to their tremendous potential for a broad spectrum of applications. The established units for the measurement of a crucial parameter for algae growth, i.e., the light dosage in photobioreactors, are susceptible to severe criticism. Various units are currently utilized without however accounting for the volume of the culture exposed to light, which might differ depending on the reactor volume. Two new units of light irradiation measurement are proposed, namely, $\mathrm{l}\mathrm{x}\mathrm{h}$ (lux-hour) and ${\displaystyle \frac{\mathrm{l}\mathrm{x}\mathrm{h}}{\mathrm{m}\times \mathrm{d}\mathrm{a}\mathrm{y}}}$. For the latter, ${\displaystyle \frac{\mathrm{l}\mathrm{x}\mathrm{h}}{\mathrm{m}\times \mathrm{d}\mathrm{a}\mathrm{y}}}$, the parameters taken into account include the light illuminance, light exposure time, and volume and surface of the culture in the reactor, which are commonly measured. Cylindrical and flat-panel reactors are studied to determine the constant light illuminance and variant illuminance within a day period. It is shown that the unit ${\displaystyle \frac{\mathrm{l}\mathrm{x}\mathrm{h}}{\mathrm{m}\times \mathrm{d}\mathrm{a}\mathrm{y}}}$ is much more objective for expressing the light availability in photobioreactors than the current and most common expressions. The proposed parameter could be useful for comparisons of different experiments in a reactor or for up-scaling purposes. Full article

The demand for sustainable and high-nutritional food sources is forcing the industrial sector to find alternatives to animal proteins. Microalgae and macroalgae showed remarkable protein and bioactive compound content, offering a promising solution for the food industry. However, the high production cost represents the main concern related to microalgae development. Thus, strategies that can reduce production costs, preserve the environment, and improve the nutritional characteristics of microalgae are required. Exploiting water from dismissed mines could lead to energy savings in production by opening new industrial opportunities to produce microalgae. Arthrospira platensis (Spirulina) can be grown in open ponds and photobioreactors; the composition of the growth medium and the light radiation could affect its biochemical composition. This work investigated the influence of mine water with the addition of Zarrouk growth medium on the biochemical composition of the final dried Spirulina. The trials were performed in vertical tubular photobioreactors (PBRs) exposed to the same light radiance. Samples were compared with standard growing conditions using distilled water with the addition of Zarrouk medium. Spirulina strains showed good tolerance to medium/high concentrations of Cl⁻, SO₄²⁻ and nitrogen in mine water. The experiment lasted 12 days, showing significant differences in protein, lipids, and carbohydrates between trials. Spirulina grown in mine water showed higher protein levels, 52.64 ± 2.51 g·100 g⁻¹ dry weight. On the other hand, Spirulina grown in distilled water had higher lipids and carbohydrate levels, accounting for 9.22 ± 1.01 and 31.72 ± 1.57 g·100 g⁻¹ dry weight. At the end of the experiment, both trials showed similar growth and pigment concentration. The availability of a high amount of mine water at no cost and at the ideal temperature for Spirulina cultivation increases environmental sustainability and reduces production costs. The results in terms of biomass were comparable to those of standard cultivation, whereas proteins showed higher values. Moreover, coupling renewable energy sources can further reduce production costs, with promising industrial and market developments. 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

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