Search Results (84)

Short-wavelength ultraviolet radiation can impair biological systems by causing DNA damage, oxidative stress, and disruption of photosynthetic processes. Although ultraviolet C (UVC) at 254 nm is widely used as a controlled laboratory stressor, the extent to which trophic condition influences repeated UVC tolerance in phototrophic protists remains unclear. Here, we examined the response of Euglena gracilis grown under photoautotrophic or ethanol-supported mixotrophic conditions and exposed to daily UVC pulses for five days. Cell growth, photosynthetic pigments, intracellular oxidative stress measured by 2′,7′ dichlorodihydrofluorescein diacetate fluorescence, and lipid peroxidation estimated as thiobarbituric acid reactive substances equivalent malondialdehyde were assessed, together with qualitative fluorescence microscopy. Repeated UVC exposure reduced cell density in both trophic conditions, with stronger inhibition under photoautotrophy. Photoautotrophic UVC-treated cultures showed the highest oxidative stress signal, whereas malondialdehyde displayed only a non-significant directional increase. Mixotrophic cultures maintained higher cell density under UVC and showed lower oxidative stress signals than photoautotrophic UVC-treated cultures. Pigment responses also differed between trophic conditions, with increased chlorophyll a and carotenoids per cell under photoautotrophic UVC treatment, while mixotrophic pigment levels remained comparatively stable. These findings show that trophic condition shapes repeated UVC stress responses in E. gracilis and that ethanol-supported mixotrophy is associated with improved physiological robustness under the present experimental conditions. Full article

The need for new feed ingredients that could reduce methane (CH₄) emissions from dairy cattle while maintaining rumen function is essential for sustainable milk production. This study aimed to evaluate the CH₄ mitigation potential of selected microalgae and macroalgae, along with an agro-industrial by-product, using two feeding strategies, and hypothesized that lipid- and polyphenol-rich materials would reduce CH₄ production in an inclusion-dependent manner. An in vitro batch culture study (24 h) was conducted to evaluate microalgae (Euglena gracilis and Aurantiochytrium spp.), macroalgae (Undaria pinnatifida), and an agro-industrial by-product (grape marc) either as feed additives (5%) or as a partial replacement of the concentrate mixture (30%, 50%, and 70%) in a basal diet consisting of 50% Klein grass hay and 50% concentrate mixture. As a feed additive, grape marc stands out for its potential to reduce CH₄ yield by about 43.3% without adversely affecting digestibility, pH, or total volatile fatty acid concentrations. When used as feed replacements, Euglena-, Aurantiochytrium-, and grape marc-based feeds reduced CH₄ yield at the highest replacement levels (50 and 70%); however, these effects were accompanied by decreased total gas production and volatile fatty acid concentrations, indicating reduced fermentation activity. Meanwhile, at a 30% replacement level, they showed promising efficiency as alternative feeds. Overall, CH₄ mitigation depends more strongly on inclusion strategy rather than feed type. Lipid-rich microalgae showed potential as concentrate replacements up to 30%, whereas grape marc was most effective as a feed additive for reducing CH₄ emissions. Full article

The second messenger cyclic AMP (cAMP) is very likely involved in phototactic as well as gravitactic behavior of the unicellular flagellate Euglena gracilis. A slight but significant increase in cAMP was observed when cells encountered sub-threshold acceleration (0.16 × g) force after microgravity [µg]. No differences in cAMP levels were found between cells on a clinostat and 1x-controls. This observation is consistent with the ones of earlier studies. Illumination of cells resulted in a significant increase in cellular cAMP levels. After RNAi-mediated knockdown or CRISPR-Cas9 knockout of the photoactivated adenylyl cyclases PACα and/or PACβ in the photoreceptor, light-induced changes in cAMP levels were no longer observed. In parallel, phototactic behavior was abolished, supporting the essential role of photoactivated adenylyl cyclases in phototaxis. Cells spin around their length axis during locomotion (1–2 Hz). In order to generate a signal in the light direction, the cells should be capable of synthesizing and degrading cAMP within 0.5–1 s. The rapid fixation of cells upon transition from dark to light or light to dark revealed that detectable changes in cAMP-levels (increase or decrease) occur within a 100–200 ms time window, which is sufficiently fast to account for the proposed theoretical kinetics of cAMP oscillations. Full article

The positive effects of phenolic compounds in the gastrointestinal tract are influenced by dietary fibers. The aim of this work was to study the interactions between syringic acid and soluble and insoluble dietary fibers from the β-glucan group, including laminarin from Laminaria digitata, zymosan A from Saccharomyces cerevisiae and β-glucan from Euglena gracilis. Kinetic models of the pseudo-first and pseudo-second order were applied to describe the interactions in time. The stability of the complexes between syringic acid and dietary fibers was monitored at different times by the DPPH method. The water holding capacity, water swelling capacity and water solubility of dietary fibers were determined. FTIR spectra were recorded to characterize the possible binding of syringic acid and dietary fibers. The results showed that syringic acid adsorbed onto dietary fibers with different adsorption capacities. The highest adsorption capacity was observed for zymosan A (431 mg g⁻¹), followed by laminarin (382 mg g⁻¹) and β-glucan from Euglena gracilis (336 mg g⁻¹). The parameters of the kinetic models showed good agreement with the experimental data. The highest antiradical activity was found for the complex of syringic acid—β-glucan from Euglena gracilis. The FTIR spectrum confirmed the bonding of syringic acid onto dietary fibers. The interactions of polyphenols and dietary fibers are important to understand the role of dietary fibers as carriers of polyphenols. Full article

Wastewater-based microalgal cultivation enables coupling environmental remediation with the production of sustainable, value-added biomass. In this study, Euglena gracilis was cultivated under non-axenic conditions in a 2% anaerobically digested livestock wastewater (LSWW)-based medium to enhance biomass accumulation, paramylon storage, and biodiesel precursor production, while simultaneously removing residual nitrogen and phosphorus. The LSWW medium was strongly phosphate-limited relative to ammoniacal nitrogen (N:P mass ratio ~39:1), which constrained growth. Adjustment of the N:P ratio to ~10:1 by NaH₂PO₄ supplementation, together with MgSO₄·7H₂O addition, significantly enhanced biomass production, whereas trace metals and CaCl₂ provided minimal benefit. Cultivation at an initial pH of 3 resulted in substantially higher biomass accumulation than at pH 7 under xenic conditions. Under these optimized conditions, total phosphate and ammonia were efficiently removed, decreasing from 5.27 to 0.009 mg/L (99.8%) and from 57.40 to 2.11 mg/L (96.3%), respectively. Although paramylon accumulation was low in LSWW alone (~4% dry weight), short-term ethanol supplementation (0.095%, v/v, 24 h) enhanced paramylon content to ~20% dry weight. Subsequent anaerobic treatment further enhanced lipid conversion, increasing fatty acid methyl ester (FAME) content to ~45% dry weight. Collectively, low-pH non-axenic cultivation of E. gracilis in LSWW, combined with minimal nutrient supplementation, provides an integrated platform for enhanced biomass, paramylon, and biodiesel precursor production with efficient nutrient removal. Full article

Peracetic acid (PAA) has strong biocidal activity against bacteria, fungi, and spores, even with short contact times. PAA-mediated sterilization is therefore an attractive method for sterilization of growth media that have heat-labile components or when polymer-based equipment is used. However, residual PAA and co-existing hydrogen peroxide (H₂O₂) can inhibit the growth of cultivated species, necessitating a fast and reliable quenching strategy that does not require rinsing. In contrast to Fe–EDTA-based catalytic decomposition that is strongly influenced by pH, buffers, and organic nitrogen, we demonstrate a fundamentally different, stoichiometric quenching strategy using sodium dithionite that enables instantaneous and selective removal of PAA. Na₂S₂O₄ preferentially reduced PAA over H₂O₂ in a 0.03% PAA solution and achieved complete PAA reduction within 5 s, independent of pH and in the presence of nitrogen compounds. By adjusting the Na₂S₂O₄ dose, PAA could be selectively removed while allowing a small fraction of H₂O₂ to remain. When applied to the cultivation of Euglena gracilis, which tolerates low levels of H₂O₂, the PAA–Na₂S₂O₄-treated medium resulted in greater cell growth and higher paramylon production than autoclaved medium. Full article

Basidiomycete mushrooms contain complex β-D-glucans which act as immunomodulator, immune stimulants and anti-cancer agents, which can be either free or bound to proteins. The present report consists of a novel and intrinsic synchronous fluorescence and phosphorescence assay method for β-D-glucans. This analytical technique was carried out by a spectrofluorometer in the range of 250 to 750 nm with a Δλ range of 5–30 nm which exhibited peaks at 492, 540 and 550 nm by using β-D-glucan from Euglena gracilis as a standard. A micro and high-throughput method based on a microplate fluorescence reader was devised with a excitation and emissions λ of 420 nm and 528 nm, respectively. This assay method revealed some advantages over the reported colorimetric methods, since it is a non-destructive assay method of β-D-glucans in samples with a linearity range of 0–14 μg/well, correlation coefficient (r2) of 0.9961, LOD of 0.973 μg/well, LOQ of 2.919 μg/well, greater sensitivity, fast, a high-throughput method and very economical. β-D-glucans of several mushrooms (i.e., Poria coccus, Auricularia auricula, Ganoderma lucidium, Pleurotus ostreatus, Cordyceps sinensis, Agaricus blazei, Polyporus umbellatus, Inonotus obliquee) were purified by using a sequence of various solvent extractions, quantified by either spectrofluorometer or fluorescence microtiter plate reader assay and compared with Congo red assay method. Three-dimensional spectra measurements were carried out on β-D-glucans from commercial sources and medicinal mushroom strains. FTIR spectroscopy was selected to investigate the structural properties of β-D-glucans in these mushroom samples. Therefore, the present assay method is simple, fast, cheap and non-destructive for β-D-glucans from medicinal mushrooms as well as from commercial sources. Full article

Weaning stress frequently compromises intestinal integrity and nutrient absorption in piglets and induces structural perturbations in the gut microbiota. This study investigated the effects of dietary Paramylon, a linear β-1,3-glucan from Euglena gracilis, on growth and intestinal function. A total of 32 healthy, 21-day-old weaned piglets (male, castrated, Duroc × Landrace × Yorkshire) were randomly allocated to four groups: control, 0.025%, 0.05%, and 0.1% Paramylon (8 pigs/group). The results showed that 0.05% dietary Paramylon quadratically increased average daily gain and feed intake (p < 0.05). Serum TC content significantly increased, while the serum urea level significantly decreased (p < 0.05). This optimal dose was used for mechanistic exploration. Dietary 0.05% Paramylon notably enhanced ileal morphology, increasing the villus height to crypt depth ratio (p < 0.01) and significantly improving apparent nutrient digestibility and ileal β-amylase activity (p < 0.05). The expression levels of SLC7A1 and GLUT2 in ileum tissues were significantly upregulated (p < 0.05). The expression level of SLC7A7 in the liver was also increased (p < 0.05). This nutrient transport-promoting effect was further confirmed in IPEC-J2 cells, which manifested because 10 ng/mL of pure Paramylon significantly upregulated the gene expressions of SLC38A2, EAAT3, PEPT1, and GLUT2 (p < 0.05). KEGG enrichment analysis on the ileum indicated that differentially abundant metabolites were enriched in amino acid-related metabolic pathways. Furthermore, the 16s sequencing results revealed that Romboutsia was significantly enriched in the Paramylon group. In conclusion, Paramylon, as an effective dietary supplement, helps promote nutrient digestion and absorption in weaned piglets and contributes to maintaining intestinal health. Full article

Rapid evaluation of water toxicity requires biological methods capable of detecting sub-lethal physiological changes without depending on chemical identification. Conventional microscopy-based bioassays are limited by low throughput and difficulties in observing small, transparent and fast-moving microorganisms. This study applies a laser-biospeckle, non-imaging microbioassay to assess the motility responses of Paramecium caudatum and Euglena gracilis exposed to two organic pollutants, trichloroacetic acid (TCAA) and acephate. Dynamic speckle patterns were recorded using a 638 nm laser diode (Thorlabs Inc., Tokyo, Japan) and a CCD camera (Gazo Co., Ltd., Tokyo, Japan) at 60 fps for 120 s. Correlation time, derived from temporal cross-correlation analysis, served as a quantitative indicator of motility. Exposure to TCAA (0.1–50 mg/L) produced strong concentration-dependent inhibition, with correlation time increasing up to 16-fold at 500× PL in P. caudatum (p < 0.01), whereas E. gracilis showed a delayed response, with significant inhibition only above 250× PL. In contrast, acephate exposure (0.036–3.6 mg/L) induced motility enhancement in both species, reflected by decreases in correlation time of up to 57% in P. caudatum and 40% in E. gracilis at 100× PL. Acute trends diminished after 24–48 h, indicating time-dependent physiological adaptation. These results demonstrate that biospeckled-derived correlation time sensitively captures both inhibitory and stimulatory behavioral responses, enabling real-time, high-throughput water toxicity screening without microscopic imaging. The method shows strong potential for integration into automated water-quality monitoring systems. Full article

Fatty acid desaturase 12 (FAD12) is a key enzyme in fatty acid biosynthesis, responsible for converting oleic acid to linoleic acid through desaturase activity. Euglena gracilis (Euglena) is an emerging platform for the industrial production of various metabolites, including lipids. However, a comprehensive understanding of Euglena’s fatty acid biosynthesis pathways remains incomplete, posing a significant barrier to the commercialization of Euglena bioproducts. To address this gap, we employed a bioinformatics approach to identify a Euglena gracilis FAD12 (Eg FAD12). We analyzed the evolutionary relationship of Eg FAD12 with its homologs from other organisms and revealed that the three canonical histidine box motifs are conserved among FAD12s. To characterize EgFAD12, we cloned it into the pEAQ-hyperstrans vector and overexpressed it in Nicotiana benthamiana to take advantage of its endogenous fatty acid pool, which could act as a substrate. The heterologous expression of FAD12 in N. benthamiana led to an increased linoleic acid content, demonstrating the suspected desaturase activity. To further confirm the function of Eg FAD12, we performed CRISPR-Cas9-mediated knockout of Eg FAD12 in Euglena, which resulted in a drastic reduction in linoleic acid (C18:2) without compromising biomass yield or lipid content. This work advances our understanding of fatty acid biosynthesis in Euglena and will aid in its adoption as a platform for producing customized lipids. Full article

Euglena gracilis’s mixotrophic metabolism offers biotechnological potential. This study investigated how glucose, sodium acetate, ethanol, and propanetriol regulate its growth, photosynthesis, and paramylon production. All carbon sources boosted paramylon yield versus photoautotrophic controls. Ethanol and glucose were both highly effective, supporting the highest biomass accumulation (5.71 and 4.42-fold increases, respectively) and paramylon content without a significant difference between them. Ethanol supplementation enhanced chlorophyll b via coupled TCA cycle/glyoxylate shunt activity, while glucose showed the strongest tendency for high paramylon and the highest carotenoid content (13.36-fold higher). Sodium acetate triggered alkaline stress (pH 8.5), suppressing pigments and inducing spherical cells. Propanetriol reduced biomass but enhanced PSII efficiency (Fv/Fm). These results demonstrate carbon source-driven metabolic partitioning: ethanol and glucose both excel in promoting growth and storage, while additionally directing carbon toward chlorophyll b or carotenoids, respectively. These findings enable targeted bioprocess optimization: selection between ethanol or glucose can be based on the value of co-products, advancing E. gracilis as a sustainable cell factory. Full article

Brazil is an endemic region for both human and feline sporotrichosis, with Sporothrix brasiliensis being the main etiological agent. Currently, few effective antifungal agents are available for treating this mycosis in cats, and therapeutic studies remain limited. Itraconazole (ITZ) is the first-line drug; however, its effectiveness is variable. To evaluate the use of ITZ combined with β-glucans (Euglena gracilis) in feline sporotrichosis, a prospective, uncontrolled interventional study was conducted in 29 cats. Clinical cure was achieved in 21 animals (72.4%) with a median treatment duration of 10 weeks. Most of these cats presented with nasal region lesions, nasal mucosa involvement, and respiratory signs, which are commonly associated with poor therapeutic outcomes. Treatment failure occurred in 5 animals (17.2%), and 3 (10.3%) were lost to follow-up. No deaths were recorded during the study. Adverse drug reactions (ADRs) were observed in 2 cats (6.9%). These findings suggest that β-glucans may be a complementary strategy in the treatment of feline sporotrichosis, particularly in cases involving nasal lesions and respiratory signs, and may also contribute to the prevention of ADRs associated with conventional therapy. Full article

In recent years, microalgae have gained significant biotechnological importance as a sustainable source of various metabolites of industrial interest. Among these, paramylon, a polysaccharide produced by the microalga Euglena gracilis, stands out for its diverse applications in biomedicine and pharmaceuticals. E. gracilis is an adaptable secondary eukaryote capable of growing photoautotrophically, heterotrophically and mixotrophically. During photoautotrophic growth, varying light conditions impact biomass and paramylon production. To investigate the effects of varying illumination more thoroughly, we designed and built a modular photobioreactor that allowed us to simultaneously evaluate the photoautotrophic growth of E. gracilis under twelve different light conditions: seven single-spectrum lights (ultraviolet, royal blue, blue, green, red, far-red, and infrared) and five composite-spectrum lights (3000 K, 10,000 K, and 30,000 K white lights, amber light, and “Full-spectrum” light). The 24-day growing kinetics were recorded, and the growth parameters were calculated for each light regime. Both growth curves and pigment composition present differences attributable to the light regime used for cell culture. Additionally, photosynthetic and respiratory machinery functionality were proven by oximetry. Finally, our results strongly suggest that the far-red component enhances paramylon production during the stationary phase. Full article

Biomass-derived growth stimulants are widely recognized as green and economical solutions that can significantly enhance microalgae culture efficiency and optimize the biomanufacturing process of target products. In this paper, we investigated the effect of ethanol synergized with guaiacol (GA) on biomass and β-1,3 glucan accumulation in edible microalgae, namely Euglena gracilis. The ethanol-induced mixotrophic mode significantly increased biomass and paramylon production by 12.68 and 6.43 times, respectively, compared to the autotrophic control group. GA further exerted toxic excitatory effects (hormesis) on top of ethanol mixotrophic nutrition. At the optimal concentration of 10 mg·L⁻¹ GA, chlorophyll a, carotenoids, and paramylon production increased by 8.96%, 11.75%, and 16.67%, respectively, compared to the ethanol-treated group. However, at higher concentrations, the biomass and paramylon yield decreased significantly. This study not only establishes an effective combinatorial strategy for enhancing paramylon biosynthesis but also provides novel insights into the hormesis mechanism of phenolic compounds in microalgae cultivation. The developed approach demonstrates promising potential for sustainable production of high-value algal metabolites while reducing cultivation costs, which could significantly advance the commercialization of microalgae-based biorefineries in food and pharmaceutical industries. Full article