Search Results (145)

The growing demand for sustainable, functional ingredients in the food industry has driven interest in marine-derived biopolymers. Among marine sources, microalgae represent a promising yet underexplored reservoir of bioactive gel-forming compounds, particularly extracellular polysaccharides (EPSs), both sulfated and non-sulfated, as well as proteins that exhibit unique gelling, emulsifying, and stabilizing properties. This study focuses on microalgal species with demonstrated potential to produce viscoelastic, shear-thinning gels, making them suitable for applications in food stabilization, texture modification, and nutraceutical delivery. Recent advances in biotechnology and cultivation methods have improved access to high-value strains, which exhibit promising physicochemical properties for the development of novel food textures, structured formulations, and sustainable food packaging materials. Furthermore, these microalgae-derived gels offer additional health benefits, such as antioxidant and prebiotic activities, aligning with current trends toward functional foods containing prebiotic materials. Key challenges in large-scale production, including low EPS productivity, high processing costs, and lack of regulatory frameworks, are critically discussed. Despite these barriers, advances in cultivation technologies and biorefinery approaches offer new avenues for commercial application. Overall, microalgal gels hold significant promise as sustainable, multifunctional ingredients for clean-label food formulations. Full article

Ganoderma lucidum polysaccharides (GLPs) are natural compounds with a broad spectrum of biological activities. β-1,3-glucosyltransferase (GL20535) plays an important role in polysaccharide synthesis by catalyzing the transfer of UDP-glucose to extend sugar chains, but its underlying mechanism remains unclear. In this study, the regulatory mechanism of GL20535 in polysaccharide synthesis was elucidated by overexpressing and silencing gl20535 in G. lucidum. Overexpression of gl20535 resulted in maximum increases of 18.08%, 79.04%, and 18.01% in intracellular polysaccharide (IPS), extracellular polysaccharide (EPS), and β-1,3-glucan contents, respectively. In contrast, silencing gl20535 resulted in maximum reductions of 16.97%, 30.20%, and 23.56% in IPS, EPS, and β-1,3-glucan contents, respectively. These phenomena in the overexpression strains were attributed to gl20535-mediated promotion of UDP-glucose synthesis in the sugar donor pathway and upregulation of the expression of glycoside hydrolase genes. The opposite trend was observed in the silenced strains. In mycelial growth studies, neither overexpression nor silencing of gl20535 affected biomass and cell wall thickness. Furthermore, the GL20535 isozyme gene gl24465 remained unaffected in gl20535-overexpressed strains but was upregulated in gl20535-silenced strains, suggesting a compensatory regulatory relationship. These findings reveal the regulatory role of GL20535 on gene expression in the GLPs synthesis pathway and deepen our understanding of GL20535 function in the polysaccharide network of edible and medicinal fungi. Full article

Microbial extracellular polymeric substances (EPSs) are emerging as sustainable alternatives to conventional corrosion inhibitors due to their eco-friendly nature, biodegradability, and functional versatility. Secreted by diverse microorganisms including bacteria, fungi, archaea, and algae, EPSs are composed mainly of polysaccharides, proteins, lipids, and nucleic acids. These biopolymers, chiefly polysaccharides and proteins, are accountable for surface corrosion prevention through biofilm formation, allowing microbial survival and promoting their environmental adaptation. Usually, EPS-mediated corrosion inhibitions can take place via different mechanisms: protective film formation, metal ions chelation, electrochemical property alteration, and synergy with inorganic inhibitors. Even though efficacious EPS corrosion prevention has been demonstrated in several former studies, the application of such microbial inhibitors remains, so far, a controversial topic due to the variability in their composition and compatibility toward diverse metal surfaces. Thus, this review outlines the microbial origins, biochemical properties, and inhibition mechanisms of EPSs, emphasizing their advantages and challenges in industrial applications. Advances in synthetic biology, nanotechnology, and machine learning are also highlighted and could provide new opportunities to enhance EPS production and functionality. Therefore, the adoption of EPS-based corrosion inhibitors represents a promising strategy for environmentally sustainable corrosion control. Full article

Extracellular polymeric substances (EPS) are multifunctional biopolymers that have significant biotechnological potential. In this study, forty-seven strains of Rhodococcus actinomycetes were screened for EPS production and the content of its main components: carbohydrates, lipids, proteins, and nucleic acids. The Rhodococcus strains produced lipid-rich EPS (15.6 mg·L⁻¹ to 71.7 mg·L⁻¹) with carbohydrate concentrations varying from 0.6 mg·L⁻¹ to 58.2 mg·L⁻¹ and low amounts of proteins and nucleic acids. Biofilms of R. ruber IEGM 231 were grown on nitrocellulose filters in the presence of n-hexane, n-hexadecane, or diesel fuel. The distribution of β-polysaccharides, glycoconjugates, and proteins between cells and the extracellular matrix was examined using fluorescence microscopy. The observed release of β-polysaccharides into the biofilm matrix in the presence of n-hexane and diesel fuel was regarded as an adaptation to the assimilation of these toxic hydrocarbons by Rhodococcus cells. Atomic force microscopy of the dried EPS film revealed adhesion forces between 1.0 and 20.0 nN, while some sites were highly adhesive (F_a ≥ 20.0 nN). EPS biosynthetic genes were identified, with two glycosyltransferases correlating with an increase in carbohydrate production. The production of EPS by Rhodococcus cells exhibited strain-specific rather than species-specific patterns, reflecting a high genetic diversity of these bacteria. Full article

Microalgae interact with mineral particles in an aqueous environment, yet how clay minerals affect physiological processes in algal cells remains unexplored. In this study, we compared the effects of palygorskite (Pal) and montmorillonite (Mt), which respectively represent fibrous and layered clay minerals, on the physiological processes of Chlamydomonas reinhardtii. It was observed that C. reinhardtii responded differently to the treatments of Pal and Mt. The Pal particles bound tightly to and even inserted themselves into cells, resulting in a significant decrease in cell numbers from 27.35 to 21.02 × 10⁷ mL⁻¹. However, Mt was only loosely attached to the cell surface. The photosynthesis in the algal cells was greatly inhibited by Pal, with the rETR_max significantly reduced from 103.80 to 56.67 μmol electrons m⁻²s⁻¹ and the downregulation of IF2CP, psbH and OHP1, which are key genes involved in photosynthesis. In addition, Pal reduced the quantities of proteins and polysaccharides in extracellular polymeric substances (EPSs) and the P uptake by C. reinhardtii when the P level in the culture was 3.15 mg/L. However, no significant changes were found regarding the above EPS components or the amount of P in algal cells upon the addition of Mt. Together, the impacts of fibrous Pal on C. reinhardtii was more profound than those of layered Mt. Full article

Nostoc flagelliforme, a filamentous cyanobacterium inhabiting desert biological soil crusts (BSCs), has developed exceptional strategies to endure extreme environmental stresses, including severe desiccation, intense ultraviolet (UV) radiation, and drastic temperature fluctuations. These organisms must effectively sense and predict environmental changes, particularly the onset of desiccation. This review explores recent advancements in the molecular mechanisms that enable N. flagelliforme to survive under such harsh conditions, with a focus on stress signal sensing, transduction pathways, and photosynthetic adjustments. Key molecular adaptations include the production of extracellular polysaccharide (EPS) sheaths for water retention, the accumulation of compatible solutes like trehalose, and the synthesis of UV-absorbing compounds such as scytonemin and mycosporine-like amino acids (MAAs). Furthermore, N. flagelliforme utilizes a complex signal transduction network, including light-sensing pathways, to regulate responses to rehydration and desiccation cycles. This review emphasizes the integrative nature of N. flagelliforme’s adaptive mechanisms and highlights their potential for biotechnological applications, such as enhancing drought tolerance in crops and advancing ecological restoration in arid regions. Full article

Lacticaseibacillus (L.) rhamnosus CRL75 is a lactic acid bacterium (LAB) isolated from local dairy products, demonstrating significant adaptation in skimmed milk (FM75). In this context, CRL75 exhibited high microbial growth (3.63 ± 0.18 log CFU·mL⁻¹), strong acidification (9.20 ± 0.10 g·L⁻¹ lactic acid, and 2.40 ± 0.10 pH units), and increased viscosity in FM75 after 16 h of fermentation. Additionally, this LAB strain produces both capsular polysaccharides (CPS+) and extracellular polysaccharides (EPS75), contributing to a ropy phenotype (>10 cm). The purified EPS75 (70.70 ± 3.25 mg·L⁻¹) displayed low molecular weight (12.7 kDa), with galactose and glucose as its primary monomers in a 4:1 ratio. In aqueous environments, EPS75 exhibited an extended size (147 nm), a random coil structure, and macromolecular aggregation. Furthermore, vibrational spectroscopy confirmed the presence of a neutral EPS with high thermal stability. Additionally, EPS75 exhibited dose-dependent antioxidant activity, effectively reducing metal ions (Fe³⁺, Mo⁶⁺, and Mn⁷⁺) and stabilizing radicals (ABTS^•+, HO^•, O₂^•−, and HOO^•). The biopolymer also demonstrated immunostimulatory and anti-inflammatory effects in RAW 264.7 cells. In vivo assays using Balb/c mice indicated that both EPS75 and FM75 prevented constipation, suggesting their potential as natural and safe agents for constipation-related disorders. Due to its viscosifying and health-promoting attributes, CRL75 offers promising applications for functional dairy products. Full article

Pseudomonas aeruginosa biofilms, driven by extracellular polysaccharides (EPSs), exacerbate pathogenicity and drug resistance, posing critical threats to public health. While EPS biosynthesis pathways are central to biofilm formation, their distinct contributions and regulatory dynamics remain incompletely understood. Here, we systematically dissect the roles of three core EPS pathways—Psl, Pel, and alginate—in biofilm architecture and function using multi-omics approaches. Key findings reveal Psl as the dominant regulator of biofilm elasticity and thickness, with its deletion disrupting chemotaxis, quorum sensing, and 3′,5′-Cyclic GMP (c-di-GMP)/amino acid metabolism. Pel redundantly enhances biofilm biomass, but elevates flagellar synthesis efficiency when Psl is absent. Alginate exhibited negligible transcriptional or metabolic influence on biofilms. These insights clarify hierarchical EPS contributions and highlight Psl as a priority target for therapeutic strategies to dismantle biofilm-mediated resistance. Full article

Scleroglucan is the extracellular polysaccharide (EPS) produced by Sclerotium rolfsii (S. rolfsii). The low EPS titer and limited substrate utilization of S. rolfsii present significant challenges in the fermentation process, restricting industrial applications of scleroglucan. In this study, we performed a transcriptomic analysis on the mycelium of S. rolfsii fermented with different carbon sources. The key genes involved in polysaccharide biosynthesis (6-phosphofructokinase 1 (PFK1), pyruvate decarboxylase (PDC), aldehyde dehydrogenase (NAD (P)+) (ALDH3), and acetyl-CoA synthase (ACS)) were identified and their roles in the process were investigated. The supplementation of specific precursors—fructose-6-phosphate, pyruvate, aldehydes, and acetate—was shown to enhance both the polysaccharide titer and substrate utilization. By adding precursors, the titer of SEPS produced in a 5 L fermentation tank reached 48.69 ± 3.8 g/L. Notably, the addition of these precursors increased the titer of EPS fermented with sucrose (SEPS) by 65.63% and substrate utilization by 119.3%, while the titer of EPS fermented with lactose (LEPS) rose by 80.29% and substrate utilization rose by 47.08%. These findings suggest that precursor supplementation can effectively improve polysaccharide production and substrate efficiency, thereby minimizing resource waste and environmental impact. Full article

In this study, biofilm formation and the production of key virulence factors were systematically evaluated across 33 strains of Pseudomonas aeruginosa isolated from diverse hospital environments in Tunisia. Among these, 13 strains demonstrated strong biofilm-forming capacities. Adding glucose (9%, w/v) to the culture medium generally enhanced biofilm development, indicating that glucose supplementation may promote biofilm formation in clinical isolates. The 13 selected biofilm-forming strains exhibited a consistent production of critical virulence factors, including pyocyanin, rhamnolipid, and LasA protease, known for its staphylolytic activity. However, profiles of extracellular polysaccharide (EPS) production and motility showed considerable heterogeneity among the strains, suggesting a strain-specific regulation of these traits. Based on a comprehensive analysis of biofilm formation and virulence expression, strain 2629 was chosen as a model organism due to its robust biofilm-producing ability and high virulence factor output. This strain was used in subsequent in vitro assays to evaluate the anti-biofilm potential of a commercial disinfectant containing peracetic acid and other active agents. Results indicated that a 3% (v/v) concentration of the disinfectant, applied for 5 min, was nearly sufficient to eradicate the biofilm formed by the model strain. These findings underscore the importance of selecting a representative biofilm-forming strain for accurate in vitro assessments of disinfectant activity. Full article

Aerobic granular sludge (AGS) is a promising technology for wastewater treatment. Granules have a compact microbial structure and a high potential for pollutant removal. Despite its advantages, the impact of microplastics (MPs) on AGS remains poorly understood, posing a potential risk to the stability and efficiency of biological wastewater treatment processes. This study investigates the effects of polyethylene terephthalate (PET) MPs on AGS structure and extracellular polymeric substance (EPS) composition, providing new insights into the interaction between MPs and AGS. Four granular sequencing batch reactors (GSBRs) were operated with varying concentrations of PET MPs in the influent wastewater (0, 1, 10, 50 mg/L). Key findings include MP-induced changes in granule size distribution, with an increase in smaller granules (<90 µm) observed in reactors exposed to PET MPs. EPS concentrations (51–77 mg/L) exhibited significant differences among reactors, with notable shifts in protein (PN) and polysaccharide (PS) fractions. A higher PET MP dose resulted in an increased PN/PS ratio (from 1.96 to 5.40) and elevated hydrophobicity of AGS. These changes suggest that MPs can alter AGS structure and EPS composition, potentially affecting granule stability and treatment performance. This study provides novel evidence on the disruptive effects of MPs in wastewater treatment systems, emphasizing the need to address MP pollution in the context of biological treatment processes. The results contribute to a deeper understanding of the interactions between MP and AGS and form the basis for strategies to mitigate their adverse effects. Full article

The environmental treatment of endocrine-disrupting compounds (EDCs) has attracted significant attention. Nonylphenol (NP), a highly toxic EDC with widespread distribution, presents an urgent challenge requiring effective removal strategies. Although microalgae-based treatments offer environmentally friendly and cost-effective solutions, the high toxicity level of NP impedes this process. Analysis was conducted on cell biomass, cell morphology, extracellular polymeric substances (EPSs), and the degradation of nonylphenol in Chlorella pyrenoidosa treated with nonylphenol and glucose. Glucose restored the algal biomass to 2.23 times its original level, reduced cellular damage, and maintained normal physiological activities. Glucose also stimulated algal metabolism and promoted the secretion of EPSs. The polysaccharide content of soluble EPSs (S-EPSs) increased by 32.7%, whereas that of the bound EPSs (B-EPSs) increased by 55.5%. The three-dimensional excitation–emission matrix fluorescence spectroscopy of B-EPS indicated that glucose enhanced tryptophan secretion. Glucose showed great potential as a biostimulant to enhance NP bioremediation efficiency in aquatic ecosystems. This finding indicates that the nonylphenol remediation of wastewater can be integrated with microalgal biomass recovery, creating opportunities for revenue generation. Full article

Towels with complex woven structures are susceptible to biofilm formation during daily use. The composition of biofilms formed on towels used under real-life conditions has yet to be studied. Thus, we investigated the color changes, structural integrity, and biofilm development on towels used continuously for 10 weeks by 12 volunteers in specific kitchen environments. Apparent biofilms composed of bacteria and extracellular polymeric substances (EPSs) were found on all used towels. The bacteria concentrations ranged from 4 to 7 log CFU/g. Proteins were the most abundant EPS, followed by polysaccharides and eDNA. A high-throughput sequencing method was employed to investigate the bacterial diversity on the towels. The predominant bacterial genera differed from towel to towel. Kocuria, Rothia, Psychrobacter, Enhydrobacter, and Pseudomonas are genera of relatively high abundance that may originate from the human body and foods. In addition, correlations among environmental factors, major bacterial genera, physical properties, and biofilm formation of the towels were analyzed, which could provide a scientific reference for maintaining towel hygiene. Full article

The adhesion between dibenzofuran (DF) and degrading bacteria is the first step of DF biodegradation and affects the efficient degradation of DF. However, their efficient adhesion mechanism at the molecular level remains unclear. Therefore, this study first examined the adhesive behaviors and molecular mechanisms of Rhodococcus sp. strain p52 upon exposure to DF. The results showed that the adhesion between strain p52 and DF is mediated by extracellular polymeric substances (EPSs). Compared with sodium acetate as a carbon source, the percentages of glucose and proteins related to electron transfer, toxin–antitoxin, and stress responses were elevated, which were analyzed by polysaccharide composition and proteomics, and the contents of extracellular polysaccharides and proteins were increased. Moreover, biofilm analysis suggested an increase in EPS content, and the change in components increased biofilm yield and promoted loose and porous aggregation between the bacteria; this aggregation caused an increase in the specific surface area in contact with DF. The surface characteristics analysis indicated that the production of EPS reduced the absolute value of the zeta potential and increased the hydrophobicity of strain p52, which was beneficial for the adhesion of strain p52 and DF. These findings help us to enhance the understanding of the adhesion mechanisms and bioremediation of polycyclic aromatic hydrocarbons by degrading bacteria. Full article

The quest for cleaner and sustainable energy sources is crucial, considering the current scenario of a steep rise in energy consumption and the fuel crisis, exacerbated by diminishing fossil fuel reserves and rising pollutants. In particular, the bioaccumulation of hazardous substances like trivalent chromium has not only disrupted the fragile equilibrium of the ecological system but also poses significant health hazards to humans. Microalgae emerged as a promising solution for achieving sustainability due to their ability to remediate contaminants and produce greener alternatives such as biofuels. This integrated approach provides an ambitious strategy to address global concerns pertaining to economic stability, environmental degradation, and the energy crisis. This study investigates the intricate defense mechanisms deployed by freshwater microalgae Chlorella minutissima in response to Cr (III) toxicity. The microalga achieved an impressive 92% removal efficiency with an IC₅₀ value of 200 ppm, illustrating its extraordinary resilience towards chromium-induced stress. Furthermore, this research embarked on thorough explorations encompassing morphological, pigment-centric, and biochemical analyses, aimed at revealing the adaptive strategies associated with Cr (III) resilience, as well as the dynamics of carbon pool flow that contribute to enhanced lipid and extracellular polysaccharide (EPS) synthesis. The FAME profile of the biodiesel produced complies with the benchmark established by American and European fuel regulations, emphasizing its suitability as a high-quality vehicular fuel. Elevated levels of ROS, TBARS, and osmolytes (such as glycine-betaine), along with the increased activity of antioxidant enzymes (CAT, GR, and SOD), reveal the activation of robust defense mechanisms against oxidative stress caused by Cr (III). The finding of this investigation presents an effective framework for an algal-based biorefinery approach, integrating pollutant detoxification with the generation of vehicular-quality biodiesel and additional value-added compounds vital for achieving sustainability under the concept of a circular economy. Full article