This study evaluated the ability of the living biomass of the microalga Chlamydomonas reinhardtii to remove benzalkonium chloride (BAC), a widely used disinfectant and emerging aquatic contaminant, from aqueous solutions. To characterize the removal process, the toxic effect of BAC on the microalga was investigated, along with the kinetics and equilibrium isotherms. An FTIR analysis was performed. The effect of exposing the microalgae to light or keeping them in darkness on their BAC removal capacity was studied. Finally, the effect of pH on the efficiency of the process was also studied. This living biomass effectively removed BAC both in light and in darkness, although removal efficiency was significantly higher in the light when the toxic effect of the BAC was lower, which allowed for the existence of a greater number of viable cells. The highest removal efficiency reached 98.3
Arthrospira platensis (also known as Limnospira platensis) represents a rich source of bioactive molecules with potential effects on plant growth and development. However, its application as a biofertilizer or biostimulant is limited by high biomass production costs. This study evaluated the possibility of using post-phycocyanin (PC) extraction biomass for the production of plant growth promoters. The biomass was processed using different hydrolysis techniques (physical, chemical, and enzymatic), and the resulting hydrolysates were characterized by quantifying NPK content and major bioactive compounds, including polysaccharides, proteins, and amino acids. The plant growth-promoting effects of selected hydrolysates were subsequently evaluated on tomato (Solanum lycopersicum) seedlings under greenhouse conditions. PC-biomass characterization showed N, P, and K content of 4.0, 9.9, and 8.5
The increasing reliance on chemical fertilizers in agriculture has led to significant environmental concerns, including greenhouse gas emissions and nutrient pollution. To address this issue, this study assessed the environmental performance of integrating microalgae-based biofertilizer production with municipal wastewater treatment at the Bojongsoang Wastewater Treatment Plant (WWTP), Indonesia. A consequential life cycle assessment (cLCA) was conducted to evaluate three scenarios: (1) chemical fertilizer, (2) microalgae biofertilizer baseline (MBB), and (3) microalgae biofertilizer optimistic (MBO). Native polyculture microalgae strains such as Spirulina sp., Oscillatoria sp., and Microcystis sp. were cultivated using nutrient-rich wastewater and processed into biofertilizer for agricultural application. The results demonstrated that substituting chemical fertilizer with microalgae-based biofertilizer significantly reduced environmental impacts. Specifically, the MBB and MBO scenarios achieved greenhouse gas emission reductions of 11.24 kg CO₂eq kg-1 N and 18.11 kg CO₂eq kg-1 N, respectively, corresponding to a 12.5
Cyanobacterial harmful algal blooms (CHABs) impair water quality, ecosystem functioning, and public health. Although nutrient-load reduction remains essential for long-term management, short-term treatments may cause rapid cell lysis and the release of intracellular cyanotoxins. Understanding the mechanisms governing cyanobacterial death could therefore improve predictions of bloom decline and support safer control strategies. This review critically synthesizes current evidence for regulated cell death (RCD) in cyanobacteria and evaluates its relevance to CHAB mitigation. We examine orthocaspase-associated processes and processes occurring without demonstrated orthocaspase involvement, including hydrogen peroxide-induced apoptosis-like RCD, cyanobacterial ferroptosis, and death responses triggered by pyrogallic acid. We also consider recent evidence connecting RCD with natural bloom decline. Nanoparticles are evaluated as potential biotechnological tools for modulating cyanobacterial cell fate. The available evidence identifies potentially modifiable cellular processes but also reveals important methodological and ecological constraints. Biomass suppression alone does not establish an effective or environmentally acceptable outcome; cell lysis, cyanotoxin release and degradation, bloom recovery, treatment persistence, and non-target effects must also be evaluated. RCD-guided interventions could complement nutrient-load reduction and ecosystem restoration in integrated CHABs management. Their application in natural waters or controlled drinking-water treatment systems will require evidence of mechanistic specificity, target selectivity, ecological safety, and practical feasibility.
Gamma ray degraded sodium alginate has shown growth-promoting activities in various crops. Java citronella (Cymbopogon winterianus Jowitt) is an important aromatic grass with proven therapeutic and medicinal values attributed to its essential oil (EO). Various characterization techniques were employed to study both un-irradiated and irradiated sodium alginate samples. These techniques deciphered that irradiated sodium alginate (ISA) samples possess remarkable characters such as small particle size along with high content of carbonyl (C=O) group and guluronic acid (G). The efficacy of the graded concentrations of ISA was tested on Java citronella grown in pots in terms of growth, photosynthesis and allied parameters and EO production of the plant. There were two control treatments for this experiment, double distilled water (DDW) and un-irradiated sodium alginate. Amongst the different ISA concentrations applied, 60 mg L-1 of ISA (ISA-60) proved optimum in escalating growth as well as various parameters concerned with the photosynthesis and yield at 150 days after planting. This treatment promoted the photosynthetic machinery by improving PSII activity, leaf gas exchange, enzymatic activities and total carbohydrate content. It also augmented EO content and yield. The gas chromatography-mass spectrometry (GC-MS) analysis of EO showed that the content of major active constituents such as citronellal and geraniol content were also increased by the treatment. However, the citronellol and geranyl acetate content were reduced by the application of ISA-60.
Is the use of commercially available biostimulant an effective intervention to promote growth rate and/or invigorate declining seedstock quality in algaculture? The use of Ascophyllum Marine Plant Extract Powder (AMPEP), derived from the cold temperate brown seaweed Ascophyllum nodosum, in eucheumatoid seaweed research has mostly reported positive effects. Biostimulants are described as a biological substance or effector independent of the growth-enhancing effects of its inorganic nutrient contents, i.e., when applied to crops, stimulate plant physiological processes benefiting nutrient uptake and use efficiency, tolerance to abiotic stress, and promote crop growth and quality. In this study, the presumptive positive effect of AMPEP on the growth of Kappaphycus alvarezii as reported in the literature was re-evaluated with systematic assessment of the ambient seawater nutrient status. Under naturally nutrient-replete seawater with continuous flow-through system in a land-based nursery with semi-natural environmental conditions, AMPEP application using different concentrations (high, from 10 – 1000 mg L−1 and low, from 1 – 3 mg L−1) and different incubation times (from 15 h to 30 and 60 min) did not produce statistically detectable improvements in daily growth rate or shoot induction relative to the control in the short term (20 and 28 days) experiments. Results of our study showed that the presumptive biological molecules, e.g., phytohormones and polysaccharides, present in AMPEP that may function as plant growth regulators did not elicit significant positive effects compared to the negative (nutrient-replete natural seawater) control. Further study is needed to look into the presence of any active biomolecules in commercial biostimulant products, their concentrations and role in eliciting responses that are presumed to help crops resist disease or survive harsh environments, e.g., high temperatures, and stimulate higher growth rate.
The viability of kelp microscopic gametophytes is currently analyzed using subjective visual methods based on bright-field (BF) microscope images. Fluorescence microscopy (FM) can be employed, but the dyes used can be toxic and blue/UV light intensity may induce gametogenesis. This study aimed to develop a non-invasive and accurate methodology for assessing gametophyte viability over time, using FM observation of chlorophyll autofluorescence emitted by live gametophytes. Six isolated gametophyte strains of Laminaria ochroleuca (Italy), maintained at CCMAR Biobank, were cultured in triplicate (female, male, and both sexes combined) in Petri dishes containing 10 mL of half-strength Provasoli’s enriched seawater medium (PES), under red light for 1 month. Survival and growth were assessed on days 1, 7 and 14 by photographing 20 fields-of-view, both in BF and FM. Then, cultures were transferred to white light to induce gametogenesis and test whether the autofluorescence analysis (AFA) method affected gametophyte reproduction. Image analysis was performed using FIJI software either by manually counting live gametophytes (survival) and measuring their area (growth), or by implementing a machine-learning (ML) model using FIJI’s WEKA segmentation plugin. Results revealed that both methods were correlated, validating our ML model. However, the AFA method was faster and more accurate than BF image analysis, especially for male gametophytes, and did not compromise reproductive capacity. After 9 days under white light, sporophytes were present in mixed cultures. The AFA method provides a reliable technique for assessing gametophyte viability without compromising gametogenesis.
This study investigated the cytotoxic effect of the herbicide glyphosate (25–200 μg L−1) on the marine diatom Thalassiosira excentrica. It was found that glyphosate at a concentration of 25 μg L−1 inhibited culture growth by 1.5 times after 72 h, and at 100 μg L−1, cell numbers decreased by 6 times compared to the control, with the growth rate not exceeding 0.2 day⁻1. Concentrations above 100 μg L−1 caused complete culture death. The herbicide was shown to induce increased intracellular oxidation, reduce cellular metabolic (esterase) activity, and decrease chlorophyll fluorescence intensity, as confirmed by confocal microscopy (formation of hollow hexagonal structures, reduction in the number of chloroplasts). A dose-dependent decline in photosynthetic activity parameters was recorded: the relative variable fluorescence (Fv/Fm) from 0.76 (control) to 0.21 (200 μg L−1), and the maximum relative electron transport rate (rETR) in photosystem II from 0.47 to 0.14, indicating damage to PSII reaction centers and disruption of electron transport. Morphological nuclear abnormalities (deformation, fragmentation, chromatin scattering) and mitochondrial disturbances (peripheral organelle localization, loss of membrane potential against the background of cytoplasmic vacuolization) were also revealed. Thus, the cytotoxic effect of glyphosate on T. excentrica is mediated by oxidative stress, inhibition of photosynthesis and metabolic activity, as well as nuclear damage and mitochondrial dysfunction, collectively leading to growth suppression and culture death.
The industrial exploitation of Haematococcus lacustris for astaxanthin production is constrained by low biomass productivity and energy-intensive extraction processes required to disrupt the rigid cyst cell wall. This study investigated the combined effects of magnesium aminoclay nanoparticles (MgAC; 0.01 − 0.50 g L−1) and CO2 concentration (0.04 − 15.0
Efficient biomass harvesting remains a major bottleneck in the commercial production of polyunsaturated fatty acids (PUFAs) from thraustochytrids. This study investigates the influence of pH and food-grade divalent cations (Mg2⁺ and Ca2⁺) on the flocculation performance of Aurantiochytrium sp. SW1, with emphasis on flocculation efficiency, surface charge modulation, floc morphology, and lipid quality. Acidic conditions (pH 3) induced auto-flocculation, while highly alkaline conditions (pH 13) triggered sweep flocculation driven by in situ precipitation of metal hydroxides. At 20 mM, magnesium and calcium achieved comparable flocculation efficiencies (76.6
The co-culture of an aerial microalga and a nitrogen-fixing bacterium was investigated under aerial-phase conditions to clarify their mutual exchange of carbon (C) and nitrogen (N). In this system, the microalga supplied organic C, whereas the bacterium provided inorganic N. The aerial microalga Coelastrella rubescens KGU-HN001, previously isolated from the surface of steel signs, and the N-fixing bacterium Rhodobacter sphaeroides were grown as biofilms on a medium lacking external C and N sources under aerial-phase conditions. During co-culture under aerial-phase (i.e., aerobic) conditions for 14 days, the number of algal cells increased by about 5.7 times, the total organic C content in the cell suspension increased threefold, and the total N content doubled, indicating active C and N fixation. After 7 days, algal cell numbers and biomass in bilayer biofilms were 1.8- and 1.6-fold higher than those in algal monoculture. These results demonstrate that both microorganisms grew under aerial-phase (i.e., aerobic) conditions by mutually supplying essential nutrients.
Understanding seasonal and spatial variation in the biochemical composition of Ulva rigida is important for evaluating its biomass quality and potential utilization pathways. In this study, dry matter, protein, lipid, ash, and chlorophyll-a contents of U. rigida collected from three coastal regions of the Marmara Sea — İzmit Gulf, Gemlik Gulf, and the Çanakkale Strait — were investigated seasonally during summer, autumn, winter, and spring. Simultaneously, seawater temperature, salinity, pH, and dissolved inorganic nutrient concentrations were measured. The results showed that the biochemical composition of U. rigida varied markedly among seasons and sampling regions. Dry matter content ranged from 8.62 to 18.78
Seaweed farming is a growing global industry with significant potential for environmental and economic benefits. While East and Southeast Asian countries dominate current production, interest and investment in kelp farming are expanding to other regions, including Africa. In South Africa limited information is available on the cultivation potential of the three local west coast kelp species Ecklonia maxima, Laminaria pallida and Macrocystis pyrifera. This study was conducted as part of the South African Kelp Farming Project (SA KFP) and is the first full life cycle cultivation of the three species in an aquaculture setting over the same 8-month period in Africa. All three kelp species were grown in the hatchery/nursery to 1 cm in 49 days (at 15 ℃, a 16 h L:8 h D photoperiod, GeO2 in the first two weeks, half strength PES from the second week onward, spore concentration of 2000 spores mL−1 for E. maxima and L. pallida, and 5000 spores mL−1 for M. pyrifera). To overcome sedimentation and biofouling pressure at the grow-out site, an at-sea weaning step was introduced where juvenile sporophytes were grown for 2 weeks to 2.0–2.5 cm. Results of the 6-month grow-out period demonstrated that all three species can be cultivated in an aquaculture setting but that a good understanding of the spatiotemporal variations in environmental and biological factors at any particular site is critical before full-scale operations are attempted. The methodologies used in this study provide a foundation from which a kelp farming industry in South Africa could potentially develop and improve on.
The study investigated the interactive effects of CO2 (420 μL L-1 atmospheric CO2, AC; 1000 μL L-1, high CO2, HC) and nitrogen (nitrate: 0, 500, MN; 1500, HN and 4500, SHN μmol L-1) on the growth, chlorophyll fluorescence characteristics and biochemical compsition of the red alga Gracilariopsis lemaneiformis. Algae were acclimated to varying CO2 and nitrogen levels at 20 °C for 15 days, followed by measurements of relative growth rates (RGRs) and biochemical composition. To assess the impact of long-term acclimation on acute thermal resistance, short-term (2 h) rapid photosynthetic responses were measured across a 15-35 °C range. Results showed that HC significantly reduced the RGRs by 15.21
Marine algae contain a vast array of bioactive molecules with diverse uses. One of their interests is to apply seaweed-derived nanoparticles or polysaccharides as bio-stimulants of seed germination for plant growth promotion. Two products derived from the green alga Ulva lactuca were selected as apriming tool for maize seeds. First, the polysaccharide ulvan was characterized using EDX, SEM, XRD, and HPLC. Second, the phycosynthesized selenium nanoparticles (USeNPs) were characterized using SEM and TEM, showing their smooth spherical shape. This study investigates the impact of selenium nanoparticles (USeNPs) with concentrations of 0.5, 2.0, and 5.0 mg L-1 and ulvan with concentrations of 0.2, 1.0, and 5.0 g L-1 on the growth and morphological features of maize plants grown for a period of 14 days. Fresh and dry biomasses for shoots and roots, as well as leaf area, shoot height, and protein profile, have been evaluated. Also, the elemental content of both seeds and leaves was estimated. The findings indicated that priming maize seeds with these compounds extracted from U. lactuca significantly enhanced all measured growth attributes of maize plants according to their concentrations. We recommend using green nanoparticles or soluble polysaccharide extracts from seaweeds as bio-stimulants and an eco-friendly method of sustainable agriculture to minimize environmental damage.
A novel approach to the isolation of commercially valuable carotenoids from cyanobacteria is suggested. The protocol avoids the application of costly column chromatography. As an example, the isolation of myxoxanthophyll and oscillaxanthin from Limnospira (Spirulina) platensis (Gomont) K.R.S.Santos Hentschke is described. The method is based on the surface-active properties of a unique carotenoid-lipoprotein complex, which accumulates at the chloroform-water interface and can be easily extracted. The complex is composed of myxol 2'-α-L-quinovoside, oscillol 2,2'-di-α-L-quinovoside, and lipoproteins. The mass fraction of carotenoids in the complex was 23 ± 7
Botryococcus braunii strain Showa (race B) is a green microalga able to release long chain hydrocarbons, suitable for use as energy-rich compounds for biofuel applications, but also for high-value markets, like cosmetics. Its ability to grow in annular reactors up to 60 L was investigated. As expected, biomass productivities were rather low, with a maximum average of about 120 mg L−1 day−1. Optimization of culture conditions (e.g., cell concentration, temperature, light period, light quality) is necessary to increase biomass productivity. The main weaknesses emerged were sensitivity to high light coupled to low temperatures and susceptibility to contamination by competing phototrophs. Hydrocarbon content was quite constant, reaching 26–28
The Insulin-like Growth Factor 1 (IGF1) is a small ( 7.6 kDa) protein-hormone primarily generated in the liver of mammals. It has a similar structure to insulin, and functions to support cell growth and development. As a result, IGF1 is in high demand in the biopharmaceutical, biomedical, and research fields. In eukaryotic photosynthetic systems, over-expression of this and other proteins has been met with limited success. The current study used Synechocystis sp. PCC 6803, a freshwater, single-celled cyanobacterium, as a host system to produce the IGF1 through recombinant DNA technology. To stabilize and enhance IGF1 accumulation in the cells, fusion constructs of the codon optimized IGF1 gene with the β-subunit (cpcB gene) of phycocyanin were designed. The resulting transgenic strains accumulated significant amounts of recombinant IGF1 in direct proportion to phycocyanin in Synechocystis. Quantitative aspects of the work, including the culture biomass yield in photoautotrophic and mixotrophic growth conditions, and the amount of recombinant fusion protein (CpcB*IGF1), as a fraction of total cellular protein in Synechocystis are reported. Further, antibody specificity is used as a tool to examine the effect of different fusion orientations between the CpcB and IGF1 proteins, needed to inform of optimal conditions for IGF1 functional properties. The work adds to the concept of cyanobacteria serving as cell factories for the renewable photosynthetic generation of biopharmaceutical proteins from sunlight, carbon dioxide and water.
The development of sustainable biofertilizers based on phototrophic microorganisms requires a better understanding of the agronomic potential of different biomass-derived products. This study presents a comparative assessment of the effects of native biomass and cell debris of the cyanobacterium Limnospira platensis B-12619 on the growth and physiological status of garden cress (Lepidium sativum) under controlled conditions. Root application of native L. platensis biomass stimulated plant morphometric parameters and enhanced aboveground biomass accumulation compared with the control. Weekly application of 10 mg cyanobacterial biomass increased dry aboveground biomass of L. sativum from 15.9 ± 1.9 mg in the control to 95.9 ± 8.4 mg after 50 days of growth. Processing residues (cell debris) remaining after phycobiliprotein extraction also promoted plant growth, but their effects were weaker, resulting in approximately 2–threefold lower biomass accumulation relative to native biomass treatment. Native biomass application reduced anthocyanin accumulation, a stress marker in L. sativum, from 5.60 ± 0.30 to 0.27 ± 0.08 mg g−1 dry weight after 50 days, indicating reduced physiological stress and an improved plant adaptive status. Estimated biofertilizer efficiency reached 37 – 51
At present there is an increasing trend in night-time illumination of urban landscape, especially in historic and heritage cities, which is known to affect the growth and diversity of phototrophic biological colonisation forming subaerial biofilms (SABs) on architectural heritage. Although previous studies have demonstrated that phototrophic (mainly algal) SABs thrived well under blue LEDs, whereas red and especially green LEDs exert a biostatic effect, the optimal duration of illumination required to achieve these effects remains largely unexplored. In this study, ornamental LED illumination lasting 2, 4, 6 and 8 h using red, green, blue and warm white (positive control), along with no LED (i.e. darkness, negative control) were compared over phototrophic SABs, with 16 h of daylight, recreated in the laboratory for 35 days. At the end of the experiment, SABs were analysed by PAM fluorometry and characterised their diversity by morphology characters, biofilm biomass was measured by wet weighing and cell counting and phototrophic pigment content quantified. A duration between 4 and 6 h of green LED light, and at lesser extent red LED light, reduced SAB development, while a period of 8 h of blue LED light was optimal for further growth. Both red and green LED light increased the proportion of cyanobacterial cells. Light colour, rather than illumination duration, influenced SAB community composition.
