Search Results (1,708)

This review highlights the significant capacity of microalgae to produce a wide range of phenolic compounds and other secondary metabolites. It discusses the major abiotic stress factors affecting microalgal cells and their influence on secondary metabolite production and accumulation. Microalgae synthesize numerous bioactive compounds that contribute to their biological significance, such as antimicrobial, antioxidant, and antiviral properties. These biological properties make microalgae promising resources for various applications in pharmaceuticals, functional foods, biofertilizers, biopolymers, and other industrial sectors. Moreover, several abiotic stressors—such as salinity, light intensity, chemical exposure, and heavy metals—have been reported to stimulate the biosynthesis of secondary metabolites in microalgae. These stress conditions are often associated with increased production of protective compounds that help mitigate reactive oxygen species (ROS)-mediated oxidative stress within algal cells. This review also summarizes the impact of abiotic stress on key classes of secondary metabolites, particularly phenolic compounds, carotenoids, and flavonoids, whose concentrations tend to increase under stress conditions. Understanding the relationship between oxidative stress and secondary metabolite biosynthesis in microalgae may provide valuable insights for optimizing their biotechnological and industrial applications. Full article

Organic amendments can alter soil structure, root development, and carbon cycling, yet their coordinated effects remain unclear. Based on a long-term field microplot experiment established in 2009, four amendment systems with equivalent annual N, P, and K inputs but differing in amendment properties and nominal annual organic-material C inputs were compared: maize straw with NPK (CS), pig manure compost with NPK (PMC), biochar with NPK (BIO), and biochar-based fertilizer (BF). After 15 years, dry-sieved aggregate distribution, CT-resolved air-filled pores (>30 μm), peanut root morphology, and easily oxidizable organic carbon (EOC), microbial biomass carbon (MBC), and dissolved organic carbon (DOC) were determined. PMC had the highest CT-resolved total and connected porosities (19.01% and 10.86%), a greater proportion of small macroaggregates, and the largest root surface area. CS produced a greater proportion and mean size of large dry-sieved aggregates and the highest bulk-soil MBC content. BIO and BF showed lower CT-resolved total porosity but greater isolated porosity, anisotropy, mean pore diameter, and pore fractal dimension (collectively termed CT-resolved macropore heterogeneity); these treatments were also associated with greater root volume or length and increased EOC and DOC contents in small macroaggregate- and microaggregate-sized fractions. Root length correlated more strongly with macropore heterogeneity than with total porosity. Because measurements were obtained once from 12 microplots, these relationships and SEM results represent exploratory associations rather than causal pathways. Overall, traditional amendments were associated with aggregation or macropore connectivity, whereas carbonized amendments were associated with greater macropore heterogeneity. BF had the highest percentage of EOC in TOC (52.45%), indicating a greater relative contribution of labile carbon, not increased stable carbon stock. Full article

Organic amendments derived from agro-livestock residues offer a promising approach for soil restoration and nutrient recycling within circular economy frameworks. Nevertheless, their agronomic efficacy and environmental suitability may be contingent upon the formulation of the amendments and the properties of the soil. This study presents a preliminary evaluation of customized organic amendments derived from solid materials, such as biochar and green compost, and liquid residues, including cattle manure slurry, urban compost tea, and cattle digestate. These were applied either individually or as solid–liquid mixtures to two distinct Iberian soils. The study involved amendment characterization, seed germination assays, and a two-month greenhouse experiment with barley (Hordeum vulgare L.) to assess the effects on soil physicochemical properties, microbial activity, and plant development. The solid–liquid impregnation process facilitated the transfer of nutrients and potentially limiting elements from liquid residues to solid matrices, thereby altering amendment composition and mitigating some risks associated with the direct application of liquid residues. Mixtures based on biochar and compost generally alleviated excessive salinity and trace metal constraints, although responses varied depending on the liquid amendment and soil type. Biochar-containing amendments markedly increased soil total carbon, suggesting their potential to contribute to soil carbon sequestration. The effects of amendments were strongly dependent on soil type: acidic soil exhibited more pronounced pH improvement, whereas the carbonate-rich alkaline soil buffered several chemical changes but was more susceptible to alkalinization and sodium inputs. Urban compost tea consistently exhibited inhibitory effects on germination, plant development, and dehydrogenase activity, although these effects were partially mitigated when combined with solid amendments. Overall, the findings underscore the potential of tailored amendment mixtures to enhance residue valorisation, while highlighting the necessity for soil-specific evaluation prior to field application. Full article

Natural products derived from plants and microorganisms remain promising alternatives to synthetic chemicals and conventional substances across a wide range of fields, including pharmaceuticals, agriculture, and industry. They also play an important role in the development of sustainable biopesticides and biofertilizers. Chemically, natural products can be grouped into overlapping structural and biosynthetic categories, including alkaloids, terpenoids, flavonoids, glycosides, saponins, and polyketides. Each group reflects distinct chemical characteristics and associated biological functions. This overview highlights the main findings from the Molecules Special Issue: “Natural Products: Isolation, Analysis and Biological Activity, 2nd Edition”, focusing on three categories: (i) plant protection, plant health, and plant biotechnology; (ii) functional foods and health-promoting formulations; and (iii) therapeutic natural products and derivatives. Exploring the mechanisms of action of natural products is essential for ensuring safety and optimizing sustainable resource use. This understanding drives critical innovations across drug discovery and materials science. Ultimately, such research reinforces their cross-disciplinary significance for advancing human health and promoting environmental sustainability. Full article

Climate change and increasing demand for local protein resources offer a significant reason to introduce soybean (Glycine max (L.)) in Lithuania, which is beyond soybean’s typical distribution area in Europe. This study was carried out to examine the effect of microbial biostimulant inoculation in combination with chemical micronutrients on soybean under the edaphic condition of Lithuania. A three-year field trial (2023–2025) tested five treatments, including uninoculated control, Arthrobacter pascens (AP), Bradyrhizobium japonicum (BJ), BJ + AP, and BJ + AP combined with micronutrients (BJ + AP + MN) on soybean biomass, nodulation, growth, quality, yield, and yield components. BJ alone promoted most of the crop traits because the northern soil lacks biological nitrogen fixation rhizobia. It established nodulation, increased SPAD value, shoot biomass (81%), plant height (19.16%), root biomass (40.1%), protein (6.9%), pods per plant, and grain yield (33.2%) over the uninoculated control. Moreover, AP also elevated biomass and yield components significantly without nodule formation. The effects of combined biostimulant treatments in many cases were not significantly different from the single treatment of BJ. All the treatments exhibited stable performance in growing seasons, although with year-to-year climatic variation. The year 2025 gave the highest biomass and yield because of the good precipitation and temperature over that year. The most positive response of soybean grain yield was observed with inoculation of BJ + AP, which increased grain yield by 35.65% over the untreated control. This study highlights the potential of the novel epiphyte Arthrobacter pascens 13LEP5 as a highly efficient, nodule-independent biofertilizer that can match or exceed the performance of traditional inoculants in soybean production. This study suggests identifying rhizobial inoculation as a strong climate-smart strategy for the launch of a productive, low-input, organic soybean system as an expansion poleward cultivation under the edaphic condition of Lithuania. Full article

Recovering nitrogen from wastewater is vital for a circular economy, yet conventional air stripping is limited by aerodynamic backpressure and CO₂-induced pH drops. This study evaluates a novel pilot-scale engineering approach for municipal reject water, integrating chemical phosphorus precipitation with a fundamentally redesigned ammonia stripping column. Upstream calcium hydroxide dosing achieved >99.9% phosphorus recovery and spontaneously alkalized the effluent (pH > 12.1), eliminating supplementary caustic addition. The downstream stripping column utilized negative-pressure (vacuum) operation and high-pressure liquid atomization to maximize mass transfer while preventing flooding and alkalinity neutralization. Comprehensive on-site testing established a clear mathematical relationship between aerodynamics and efficiency. Results demonstrate that high-efficiency recovery requires gas-to-liquid (G/L) ratios exceeding 70:1, a threshold uniquely unlocked by this negative-pressure design. Under optimal conditions, the continuous-flow system achieved 87.6% ammonia removal. A low-resistance acid scrubber captured ~100% of the volatilized ammonia (exhaust 0–1 ppm), producing a concentrated ammonium sulfate bio-fertilizer. This integrated technology provides a scalable, applied engineering blueprint for advancing sustainable Water Resource Recovery Facilities. Full article

Magnetic-field-associated treatments have been investigated as possible modulators of microbial and plant–soil processes, but evidence for their effects on soil and rhizosphere bacterial communities remains fragmented and methodologically uneven. This review evaluates whether current literature provides credible evidence that magnetic-field-associated treatments affect bacterial communities in soil and rhizosphere-associated systems. The final review retained 65 publications, including 35 original studies in the qualitative evidence synthesis. The most mechanistically informative evidence comes from isolated bacterial strains and engineered microbial systems, where magnetic exposure has been associated with context-dependent changes in electron transfer, biofilm-related traits, oxidative-stress responses, nutrient-transformation processes and reactor performance. However, many community-level studies in engineered systems relied on single-reactor designs, duplicate reactors, endpoint-only sequencing or unclear sequencing replication, limiting their generalizability to soil ecosystems. Evidence from soil and coupled plant–soil systems is more directly relevant to agriculture but remains causally unresolved. Reported changes in bacterial-community composition, nutrient availability, enzyme activity and plant–soil conditions are best interpreted as system-level associations rather than as proof of direct magnetic-field effects on microorganisms. Material-mediated studies involving magnetic or Fe-containing amendments and observational studies from geomagnetic anomalies provide contextual information but cannot be used as direct evidence for magnetic-field effects. Overall, current evidence is preliminary and insufficient to support magnetic-field-associated treatments as practical tools for agricultural microbiome management. Future progress will require well-controlled experiments with sham controls, independent biological and exposure-unit replication, explicit exposure characterization, separation of plant-, soil-, and material-mediated pathways, and functional validation beyond taxonomic community shifts. Full article

Systemic biologicals have emerged as a disruptive technology for overcoming the limitations of conventional biologicals. The effectiveness of systemic and conventional biological products in improving the growth and yield of two carrot cultivars was compared. Carrot plants were inoculated with either systemic or conventional biofertilizers and nematicides, and various growth parameters and yields were compared. As expected, the first indicator of the proper functioning of the systemic biofertilizer was increased chlorophyll content (two-variety averages: systemic = 17.1, conventional = 11.8, control = 10.9 mg g⁻¹ FW). The results indicated the superior performance of the systemic biologicals in carrot production. The two-variety average yield increased by 11.92 t ha⁻¹ (32%) in plants inoculated with systemic biologicals compared with the control plants and by 6.62 t ha⁻¹ (15.4%) compared with plants inoculated with conventional products (p ≤ 0.05). For the biological nematicides, the two-variety average damage rate was 10.15% in plants treated with the systemic bionematicide, 21.15% in plants treated with the conventional bionematicide, and 31.6% in non-inoculated plants. Analyses revealed the presence of microorganisms in plants inoculated with systemic biologicals, although beneficial fungi were detected at relatively low levels. In conclusion, systemic products offer a more robust and consistent technology for improving crop health and yield and are considered the next generation of biologicals. Full article

Partial replacement of chemical fertilizers, particularly nitrogen fertilizers, with biological fertilizers is considered an effective strategy for reducing the negative environmental impacts associated with excessive fertilizer use. This study aimed to optimize N use through the application of bacterial-based biofertilizer, specifically plant growth-promoting rhizobacteria (PGPR), in different maize cultivars under semi-arid conditions. A randomized complete block design (RCBD) arranged in a split-plot arrangement was used, with the three hybrids (Shahkar, Bumbus and DK 7024) assigned to the main plots and different N treatments allocated to sub-plots. The field experiment was conducted during two consecutive spring seasons (Feb to June 2024 and 2025). The N treatments were defined as follows: control, 100% recommended N (200 kg/ha), 100% N with Pseudomonas stutzeri, 100% N with Bacillus subtilis, 100% N with Enterobacter sp., 50% N with Pseudomonas stutzeri, 50% N with Bacillus subtilis, 50% N with Enterobacter sp., 100% Pseudomonas stutzeri, 100% Bacillus subtilis, and 100% Enterobacter sp. The N treatments included synthetic fertilizer alone at the 100% recommended N rate and a combination of 100%, 50% and 0% of recommended levels with three N-fixing bacterial strains. Among the hybrids, DK 7024 exhibited the highest 1000-grain weight (349 g and 362.5 g), grain yield (6756 and 6971 kg ha⁻¹) and total dry matter (17,500 and 18,368 kg ha⁻¹) in 2024 and 2025, respectively. Among N levels, maximum 1000-grain weight, grain yield and total dry matter were noticed in 100% N with Enterobacter sp.: 402 g, 8446 kg ha⁻¹ and 21,656 kg ha⁻¹ in 2024 and 421 g, 8684 kg ha⁻¹ and 22,237 kg ha⁻¹ in 2025. Nitrogen application increased grain yield and total dry matter production; however, the treatment combined with 100% recommended synthetic N fertilizer with biofertilizer (Enterobacter sp.) showed superior performance compared with 100% N applied through only the synthetic fertilizer. The interaction between maize hybrids and N levels was statistically non-significant, suggesting that 100% N plus biofertilizers could be an effective strategy for achieving higher yields across different maize cultivars. Additionally, the beneficial effects of PGPR may contribute to sustainable agricultural practices. Further research is recommended to evaluate strategies involving reduced-N inputs combined with biological fertilizer, including the application of 100% N with biofertilizer. The present study suggests that N application in combination with biofertilizers has the potential to improve crop growth while promoting sustainable crop production. Full article

Rotating algae biofilm reactors (RABRs) have been shown to remove nutrients from wastewater and to cultivate algae for bioproducts. Another key variable in RABR technology for cultivating microalgae biomass is light intensity. The goal of this study was to address a gap in the design and operation of algae biofilm reactors by analyzing the effects of light intensity on biomass quality and quantity, chemical precipitation of phosphorus, and phosphorus uptake into biomass. This study utilized a triplicate laboratory-scale experiment with PAR intensities from 10 to 2000 µmol m⁻²·s⁻¹. Municipal wastewater anaerobic digester effluent (ADE) was utilized as nutrient-rich growth media. The greatest intensification of biomass was observed at 2000 µmol m⁻²·s⁻¹ for a microalgae biomass surface area productivity of 12.8 g·m⁻²day⁻¹, and 95% phosphorus removal. Increasing light intensity was correlated with an increase in solution pH, due to photosynthesis, that was observed to increase precipitation of phosphorus salts in addition to phosphorus uptake into biofilm biomass. Both mechanisms of phosphorus removal (chemical and biological) are favorable for bioproducts, specifically bioplastic and biofertilizer. This research is useful for improving engineering design and operation of algae biofilm systems treating ADE for optimization of biofilm quality for bioproducts through intensification of microalgae biofilm biomass. Full article

Welan gum, a high-molecular-weight exopolysaccharide from Sphingomonas sp., exhibits exceptional rheological stability and robust hydrogel properties, emerging as a highly promising agricultural biomaterial. In this study, we show that the application of welan gum promotes maize seedling growth by enhancing nitrogen use efficiency via the coordinated transcriptional reprogramming of nitrogen regulators and transporters. Mechanistically, welan gum activates the TOR pathway and the MAPK cascade, leading to the phosphorylation of ZmS6K and the terminal MAPK ZmMPK3-1. Notably, TOR inhibition reduces ZmMPK3-1 phosphorylation, demonstrating that TOR activity is indispensable for MAPK activation. Furthermore, the TOR components ZmTOR and ZmLST8 physically interact with ZmMPK3-1, and ZmLST8 independently enhances ZmMPK3-1 kinase activity, revealing a multilayered regulatory mechanism triggered by welan gum. In addition, welan gum upregulates MPK3-targeted defense genes, effectively reconciling the plant growth–defense trade-off. Elucidating this TOR–MAPK crosstalk provides the mechanistic basis for translating welan gum into sustainable gel-based biofertilizers. Collectively, this study uncovers a cooperative signaling network that underpins welan gum-mediated growth promotion, establishing the strong potential of PGPR-derived polysaccharide hydrogels as sustainable, functional biofertilizers for modern agriculture. Full article

Plant-growth-promoting microorganisms (PGPMs) have emerged as important biological tools for improving plant nutrition, crop productivity, soil health, and resilience to environmental stresses, contributing to more resource-efficient agricultural systems. This review provides a comprehensive overview of recent advances in PGPM research, with particular emphasis on next-generation microbial technologies, including synthetic microbial communities, advanced bioformulations, omics-based approaches, precision agriculture, and their contribution to the circular bioeconomy. This review combines a narrative synthesis with a bibliometric analysis based on a dataset of 801 English-language articles and review papers retrieved from the Web of Science Core Collection on 22 May 2026. Bibliometric mapping identified a rapidly expanding and increasingly interdisciplinary research landscape centered on microbial biostimulants, biofertilizers, circular economy, soil health, microbiome engineering, and climate-smart agriculture. This narrative synthesis highlights that advances in multi-omic technologies, microbiome research, and formulation strategies are improving our understanding of plant–microbe interactions and supporting the development of more targeted microbial products. At the same time, widespread agricultural implementation remains constrained by inconsistent field performance, limited ecological validation, formulation challenges, fragmented regulatory frameworks, and insufficient long-term biosafety assessments. Future research should prioritize long-term field validation across diverse agroecosystems, standardized efficacy and safety evaluation, integration of artificial intelligence with multi-omics datasets, development of ecologically reliable microbial consortia, and regulatory harmonization to facilitate responsible commercialization. Full article

Bio–tillage can continuously regulate the soil environment through plant roots and rhizosphere biological activities and is considered a low disturbance tillage practice that can alleviate soil compaction. However, long term chemical fertilization alone may limit rhizosphere carbon supply and weaken root–microbe interactions. Whether conservation management can coordinate root adaptation and arbuscular mycorrhizal fungal (AMF) responses to ameliorate the compacted soil environment and improve crop growth remains unclear. This study compared five treatments: chemical fertilizer alone (CN), straw return (SR), organic manure application (OM), straw return combined with organic manure application (SROM), and green manure intercropping (GM). SROM and GM showed the most pronounced soil amelioration effects. Compared with CN, SROM enhanced root tensile strength and elongation at break, increased the relative abundances of Glomus and Claroideoglomus and the accumulation of easily extractable and total glomalin–related soil protein (EE–GRSP and T–GRSP), reduced soil bulk density (BD) by 10.68% and 6.57% in the 0–20 and 20–40 cm soil layers, respectively, and increased MWD and GMD by 78.49–82.08%. The effects of GM were concentrated in the 20–40 cm soil layer, where enhanced soybean root Young’s modulus and complementary interspecific root distribution reduced BD by 7.36% and increased total porosity (TP) by 9.36%. GM also increased AMF root colonization, the relative abundance of Claroideoglomus, and soil nutrient availability. Additionally, SROM generally maintained the highest aboveground dry matter accumulation and exhibited the highest instantaneous growth rate, whereas the current–season growth benefit under GM was relatively limited. These findings highlight the key roles of roots and AMF in soil amelioration and soybean growth and provide a reference for optimizing low disturbance soil management in compacted black soil regions. Full article

This study investigates the impact of selected soil parameters and integrated fertilizer formulations on the productivity of three legume crops—mung bean, soybean, and cowpea—in order to identify the optimal strategies to maximize yields through reduced nitrogen and bio-augmentation. A five-year experiment composed of 2-year pot trials (2019–2020) and 3-year field trials (2022–2024) was conducted to assess the changes in soil parameters (N, P, K, OM, pH) and yield response of crops with varying amounts (1, 2, 4 kg) of Bradyrhizobium-based biofertilizer combined with a 25–50% reduction in mineral N fertilizer. The biofertilizer was composed of locally isolated strains, which were genetically identified in our previous reports as B. elkanii NE1-6, NE2-1, B. diazoefficiens NE1-65, Bradyrhizobium sp. NE1-19, NE1-34, and NE2-3. The results indicated that the amount of K strongly influenced yield increase for soybean (r = 0.85, p < 0.05) and mung bean (r = 0.67, p < 0.05), while the amount of N had the greatest influence on cowpea (r = 0.60, p < 0.05). Soybean yield was maximized with a 50% reduction in N fertilizer (20 kg N) combined with 2–4 kg biofertilizer, while cowpea and mung bean achieved increased yields at 25% reduced N fertilizer combined with 2–4 kg biofertilizer. This study confirms the viability of integrating Bradyrhizobium-based biofertilizer with a 25–50% reduction in mineral N fertilizer without yield loss by harnessing the efficient N-fixation ability of the strains in the consortium. Full article

Abiotic stresses increasingly threaten crop productivity, whereas reliance on chemical and resource-intensive interventions can compromise environmental sustainability. Existing literature identifies Trichoderma spp. as multifunctional biocontrol agents, biofertilizers, and microbial biostimulants capable of influencing plant growth, stress signaling, and rhizosphere processes; however, evidence remains fragmented across strains, crops, formulations, and stress conditions. This review aimed to integrate current knowledge on Trichoderma-mediated resilience to salinity, drought, heavy metals, temperature extremes, and emerging pollutants, while distinguishing experimentally validated mechanisms from statistical associations and conceptual inference. It evaluates constraints governing reproducibility from controlled studies to field deployment. The synthesis shows that selected crop–strain systems improve root architecture, photosynthesis, antioxidant regulation, osmotic adjustment, nutrient acquisition, ion homeostasis, hormonal balance, and stress-responsive gene expression. Benefits arise through coordinated delivery, root colonization, metabolite and protein signaling, physiological reprogramming, and rhizosphere modulation. Nevertheless, microbiome co-occurrence patterns do not establish causal network repair, evidence for broad heat and cold protection remains limited, and biochar co-application should not be interpreted as a carrier formulation without direct validation. Future progress requires strain- and crop-specific screening, mechanistic gene and protein studies, standardized formulations, combined-stress experiments, multi-location field trials, biosafety evaluation, and farmer-level economic assessment to develop reliable precision microbial technologies. Full article