Psychrotolerant, plant growth promoting microorganisms represent valuable allies for sustainable agriculture in cold-stressed environments. This study employed whole-genome sequencing and comparative genomics to characterize three such psychrotolerant bacterial isolates possessing plant growth promoting traits. Average Nucleotide Identity (ANI), Type (Strain) Genome Server and phylogenomic reconstruction identified the isolates as Comamonas jiangduensis, Pseudomonas rhodesiae, and a putative novel Acinetobacter species. Functional profiling using PGPg_Finder revealed that all isolates possessed genes associated with plant growth promotion and abiotic stress tolerance, with P. rhodesiae boasting the most extensive repertoire of plant-beneficial genes. Pangenome analysis highlighted both shared and isolate-specific genetic features, providing insight into the functional differentiation among taxa. Moreover, the diverse biosynthetic gene clusters (BGCs) support the potential of these isolates in biocontrol, nutrient acquisition, and stress mitigation. RhizoSMASH analysis further indicated the genetic capacity for utilization of root exudates, suggesting rhizosphere compatibility despite the digestate origin of the isolates. Whilst predicted virulence determinants were detected in P. rhodesiae, it is postulated that these genes are related to ecological fitness and isolate resilience, rather than its pathogenicity; nevertheless, comprehensive biosafety assessment is required prior to application. Overall, the findings underscore the potential of all isolates for the enhancement of crop performance and highlight psychrophilic anaerobic digestate as an underexplored microbial reservoir. Notably, this study uniquely reports the first genome-enabled characterization of a putative novel cold-tolerant Acinetobacter species.

Psychrophilic anaerobic digestion (PAD) requires optimization to improve methane production at low temperatures (<20 °C). This study aimed to improve methane production via bioaugmentation with psychrotolerant Serratia marcescens (SM) and biostimulation with nano-additives, comprising calcium phosphate (CaP) and hematite (α-Fe2O3) nanoparticles (NPs), during batch PAD of cattle manure and food waste at 15 °C. The highest methane yields were obtained from treatment with SM and both NPs (163.9 ± 18.0 mL CH4 g−1 VS), thereafter with the combination of CaP and α-Fe2O3 NPs (143.9 ± 50.2 mL CH4 g−1 VS). The lowest yield was observed in the control (70.2 ± 4.9 mL CH4 g−1 VS) followed by treatment with SM alone (124.6 ± 20.3 mL CH4 g−1 VS). Treatment with CaP and α-Fe2O3 NPs reduced the lag phase more than the other treatments. Moreover, the addition of nano-additives biostimulated PAD without significantly altering the microbial community composition. The dominant genera included Bacteroides, Acinetobacter, and Methanosarcina (a mixotrophic methanogen) after batch PAD across all treatments. This research provides new insights on the augmentative effect of SM, CaP and α-Fe2O3 NPs on methane production and microbial community dynamics during PAD.

Dry anaerobic digestion (DAD) is increasingly recognized as a promising waste-to-energy pathway for treating high-solids organic wastes. However, the extent to which the contemporary peer-reviewed literature addresses conditions relevant to scalable implementation remains unclear. This systematic review synthesizes evidence from 148 studies on technological performance, process stability, scalability readiness, and deployment conditions. The evidence base was geographically and methodologically concentrated, with a predominance of laboratory-scale, batch-operated, and mesophilic systems. Co-digestion, pretreatment, operating-condition optimization, and recirculation were frequently investigated strategies. Methane performance varied substantially, reflecting differences in feedstock characteristics, solids content, reactor configurations, and operating conditions. Process stability remained a central concern, with pH, volatile fatty acids, and ammonia-related parameters the most frequently reported indicators, consistent with challenges associated with acidification, ammonia inhibition, and mass-transfer limitations. The scalability assessment showed that most studies provided limited evidence on advanced deployment maturity and enabling conditions, while commercial-scale implementation, financing, stakeholder engagement, and policy support were infrequently represented in the reviewed literature. The 2010–2025 peer-reviewed evidence base remains more strongly oriented toward technological and experimental optimization than integrated deployment-oriented assessment. Greater integration of long-term operational validation with techno-economic, institutional, and implementation-related evidence is needed to understand conditions for reliable and scalable DAD deployment.

Anaerobic digesters host a variety of microorganisms, and they work together to produce biogas. While bacterial and archaeal communities have been well explored using molecular techniques, fungal community structures remain relatively understudied. The present study aims to investigate the dynamics and potential ecological functions of the predominant fungi in bacteria-bioaugmented anaerobic digesters. Eight different anaerobic digesters that contained chopped water hyacinth and cow dung as feedstock at 2% total solids were respectively inoculated with eight different bacterial strains and digested anaerobically in controlled conditions. The diversity and dynamics of the fungal community of the digesters before and after digestion were monitored using high-throughput sequencing of the fungal ITS2 sub-region of the ribosomal gene. The functional potential of the fungal community was predicted using ecological guild analysis. The dominant fungal phyla were (with relative abundance ≥1%) Ascomycota and Neocallimastigomycota. Ascomycota exhibited over 90% dominance in all treatments after anaerobic digestion (AD). Aspergillus sp. was consistently dominant across treatments during AD, while prominent anaerobic fungal genera Anaeromyces, Cyllamyces, and Caeomyces decreased. Ecological guild analysis at genus level showed that the majority of the identified fungi were saprophytes, and diversity indices indicated decreased richness and diversity after AD, suggesting a negative impact of AD on fungal communities in the anaerobic digesters. The multivariate structure of the fungal communities showed clustering of treatments with similar fungal taxa. The findings from this study provide insights into the fungal ecological guild of different bacteria-bioaugmented anaerobic digesters, highlighting their potentials in bacteria-augmented systems. Identification of an anaerobic fungal group within the phylum Ascomycota, beyond the well-known fungal phylum Neocallimastigomycota, offers a new perspective in optimizing the AD processes in specialized ecosystems.

Durum and bread wheat are widely planted cereal crops that contribute immensely to global food security. To maintain and improve on crop yields, fertilizers are applied including nitrogenous fertilizers. However, there is limited research focusing on the effect of nitrogen application rate on observed and estimated durum and bread wheat yields in dryland environments. This study investigated the application of unmanned aerial vehicle (UAV) multispectral bands and vegetation indices using artificial neural networks (ANN) and multiple linear regression (MLR) models to estimate yields of durum and bread under different nitrogen fertilizer application rates. The ratio vegetation index (r = 0.29; P < 0.05) and normalized difference vegetation index (r = 0.26; P < 0.05) showed a low, but significant correlation with bread yield under 48 kg/ha nitrogen application. The ANN model outperformed MLR for yield prediction under all nitrogen rates and produced highest accuracy of R² = 0.7753, RMSE = 0.0825 t/ha under 24 kg/ha nitrogen application for durum. The key findings from this study highlight that UAV datasets and ANN models can be used to predict durum and bread yields in real-time which is beneficial for crop nutrient management. The methods from this study should be explored with more robust machine learning and larger datasets for optimal crop yield estimation.

The psychrophilic anaerobic digestion (PAD) system is a diverse and underexplored microbial ecosystem that typically harbors cold-adapted microorganisms with possible agronomic potential. The plant growth-promoting bacteria in the residue of PAD have the potential to enhance crop production, particularly during cold winter months. In this context, the characteristics of cultivable, cold-tolerant bacteria isolated from digestate obtained during PAD were investigated. Of the 20 isolates, 12 (60%) were able to solubilize phosphate from insoluble compounds at 15°C. Furthermore, nine (45%) and six (30%) isolates exhibited nitrogen fixation activity and produced indole acetic acid (IAA), respectively, while only two (10%) isolates were capable of producing siderophores. Hydrolytic enzyme production varied with cellulase production observed as a common trait since all isolates produced varying levels of cellulase ranging from 3.3±0.5 to 15.3±4 mm activity diameter. Isolates Comamonas sp._A3-1, Acinetobacter iwoffi_B5-1, and Pseudomonas sp._B5-5 displayed maximum cellulolytic activity with activity diameters of 13±2, 13±1.2, and 15.3±4 mm, respectively. However, only two (10%) of the bacterial isolates produced protease with Pseudomonas sp._B5-5 demonstrating maximum proteolytic activity as depicted by an activity diameter of 11.3±2.5 mm. Nucleotide sequence analysis of seven isolates, possessing multiple plant-beneficial traits, revealed their affiliation to three genera: Acinetobacter (57%), Comamonas (28.7%), and Pseudomonas (14%). Biolog Phenotype MicroArray plates revealed varied catabolic capability among bacterial strains, with isolate B5-5 demonstrating the highest metabolic diversity. The findings of this study revealed that cold-tolerant isolates from low-temperature AD possess promising plant growth-promoting characteristics, which indicates the potential of psychrophilic digestate for application in agriculture.

To foster resource-efficiency and a circular economy, valorisation of agricultural waste and exploration of energy-saving methods for sustainable production of bio-based nanoparticles has gained interest. This study aimed to apply a facile and novel biosynthetic approach of preparing calcium phosphate (CaP) and iron oxide (IO) nanoparticles (NPs) using extracts of Sclerocarya birrea shells. Additionally, the effect of extraction time and annealing temperature on the physical properties of the NPs were determined. Extracts of S. birrea shells were obtained via decoction for 30 and 60 min. The biosynthesized NPs were annealed at different temperatures and characterized using ultraviolet-visible spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy, as well as surface area and zeta potential analyzers. The dried and annealed CaP NPs were identified as brushite and monetite, respectively, while IO NPs annealed at 500 degrees C primarily corresponded to the chemical composition of hematite. The negatively charged, crystallite colloids of rod-like brushite and rhombohedral-like hematite NPs had surface areas of approximately 47.95 m(2)g(-1) and 22.16 m(2)g(-1), and sizes of 70.65-81.03 nm and 31.53-35.04 nm, respectively. Additionally, FTIR analysis revealed the functional reducing and capping groups in the extracts involved in NP synthesis. Refining the process parameters can lead to the specification of optimal approaches for energy-saving and sustainable development of CaP and IO NPs for downstream applications in industries such as agriculture, bioprocessing and biomedicine.

Mechanochemical reactions are highly favourable owing to their efficiency and require less or no solvents for extraction and synthesis, agreeing with green chemistry principles. Here, we explore the formation of iron(iii) oxide nanoparticles using a chemical base and/or plant material in neat and liquid-assisted grinding (LAG). Interestingly, nanorods were formed by neat grinding, whilst LAG resulted in spherical-like nanoparticles when the chemical base was used. Using Artemisia afra as a base instead of chemical base, ultra small nanoparticles were produced showing spherical-like shape by neat grinding and polyhedral shape by LAG reaction. The morphological observation also revealed that changing the metal precursor to iron sulphate or iron nitrate influences the shape of nanoparticles formed to hexagonal and spherical-like, respectively. The conditions of the mechanochemical approach employed to synthesise iron oxide nanoparticles confirmed the production of a hematite (α-Fe2O3) polymorph. The mechanosynthesis protocol presents a green approach for producing new and/or existing materials at a shorter reaction time and ambient conditions in comparison to other conventional methods reported.

Biogas is a type of gas that can be burnt to produce energy. It causes less harm to the environment than burning coal or oil, which is why it is called “green energy”. Biogas is produced by breaking down a plant or animal resource such as cow dung (poop) in an oxygen-free environment. Biogas is produced by special microorganisms that can survive and multiply without oxygen. Recently, nanoparticles have been used to make more biogas. Nanoparticles have unique features such as their extremely small size and their ability to easily react with substances. During biogas production, microorganisms can get a lot of nutrients from nanoparticles, which helps them to produce more biogas. Nanoparticles may also improve the interactions between biogas-producing microbes, further boosting biogas production. Although nanoparticles help to produce more biogas, the correct type of nanoparticles and the right amounts must be used to ensure that more biogas is produced.

BACKGROUND: Microalga-assisted wastewater treatment systems have gained attention for their efficiency in removing nutrients, chemical oxygen demand, toxic heavy metals and other dissolved compounds, while also producing valuable biomass and demonstrating high CO2 biofixation potential. The current research focuses on investigating the municipal wastewater phycoremediation and heavy metal biosorption ability of three indigenous freshwater microalgal strains: Tetradesmus reginae, Tetradesmus obliquus and Chlorella sorokiniana. RESULTS: The research findings indicate that the microalgal strains T. reginae, T. obliquus and C. sorokiniana exhibited notable performance in biomass accumulation. Specifically, the biomass accumulations were 2.215 +/- 0.002, 1.143 +/- 0.006 and 0.856 +/- 0.021 g L-1, respectively, with initial culture biomasses ranging from 0.5 to 0.6 g L-1. These strains significantly reduced toxic heavy metals (As, 46.86-60.12%; Cd, 52.96-83.18%; Cr, 73.49-82.18%; and Pb, 95.38-96.25%), nutrients (NH4+ & NO3- 100% and PO43- 78-86.41%) as well as chemical oxygen demand (46.02-67.35%), and biosequestered CO2 (0.8-0.18 gCO(2) L-1 d(-1)) during the growth period. Among the strains, T. reginae emerged as the top performer. The Fourier transform infrared spectra of the strain's biomass confirmed the presence of specific functional groups, such as -CH, -NH, -OH and -CN, which play a crucial role in ionising and reacting with toxic metal ions and protons in the wastewater. CONCLUSION: This study has shown that the isolated wild microalgal strains have promising phycoremediation and heavy metal adsorption characteristics. Moreover, they exhibit promising rates of CO2 biosequestration. These findings underscore the potential of microalga-assisted wastewater treatment systems for efficient and eco-friendly wastewater remediation, as well as biomass generation and CO2 mitigation. (c) 2024 Society of Chemical Industry (SCI). (c) 2024 Society of Chemical Industry (SCI).

Maize (Zea mays L.), a key staple crop in Sub-Saharan Africa, is particularly vulnerable to concurrent drought and heat stress, which threatens crop yield and food security. Plant growth-promoting rhizobacteria (PGPR) have shown potential as biofertilizers to enhance plant resilience under such abiotic stresses. This study aimed to (1) identify PGPR isolates tolerant to drought and heat, (2) assess their capacity to mitigate the effects of these stresses on early maize growth, and (3) analyze maize gene expression changes associated with PGPR-induced tolerance. Rhizobacteria were isolated and screened for drought and heat tolerance, alongside key plant growth-promoting (PGP) traits, including phosphorus solubilization, nitrogen fixation, and indole acetic acid production. In vitro and pot trials evaluated the effects of selected isolates on maize growth under stress, using indicators such as shoot length, root and shoot biomass (wet and dry), and leaf water content. Quantitative reverse transcription PCR (qRT-PCR) was employed to profile maize stress response genes. The identified PGPR isolates included Bacillus cereus (11MN1), Bacillus pseudomycoides (21MN1B), Lelliottia amnigena (33MP1), and Leclercia adecarboxylata (36MP8). Greenhouse trials demonstrated that L. amnigena 33MP1, L. adecarboxylata 36MP8, and a mixed culture of isolates (11MN1, 21MN1B, 33MP1, 36MP8) effectively alleviated the adverse effects of concurrent drought and heat stress in maize. Notably, qRT-PCR analysis indicated that PGPR-induced tolerance may involve the modulation of stress response genes CAT2 (catalase 2) and DHN2 (dehydrin 2), which play roles in oxidative stress management and cellular protection. The PGPR isolates identified in this study represent promising bioinoculants for enhancing maize resilience under climate-induced stresses, offering a sustainable approach to improve maize productivity, conserve water, and reduce irrigation needs in drought-prone regions.

Reducing nitrogen (N) losses and associated nitrate (NO3-) leaching and nitrous oxide emissions from agricultural land is a critical target worldwide. This is particularly urgent in areas with low fertility soils and a climate that increases the risk of N loss, such as the arid and temperate regions of South Africa. Here, we assessed the potential of fodder oats ( Avena sativa ) as a winter catch crop to deplete residual N in a field laid fallow for the previous four years, where vetch had proliferated. The soil presented a high clay content (34-44%), with the main exchangeable bases being calcium and magnesium hence, ammonium (NH4+) deposited by the vetch was expected to be rapidly adsorbed and slowly released. A significant decrease in the concentrations of NO3- (49%) and NH4+ (30%) throughout the soil profile (0-90 cm) was observed following harvest of the oats compared to the concentrations measured before sowing. The effectiveness of the oats to uptake both forms of N from top and deep soil layers enhances their potential to reduce N losses. Our results are useful to fill current knowledge gaps on N dynamics in understudied, vulnerable soils such as agricultural land in South Africa, and to advance crop rotation strategies that reduce risk of N leaching. ### Competing Interest Statement The authors have declared no competing interest.

Globally, food security has become a critical concern due to the rise in human population and the current climate change crisis. Usage of conventional agrochemicals to maximize crop yields has resulted in the degradation of fertile soil, environmental pollution as well as human and agroecosystem health risks. Nanotechnology in agriculture is a fast-emerging and new area of research explored to improve crop productivity and nutrient-use efficiency using nano-sized agrochemicals at lower doses than conventional agrochemicals. Nanoparticles in agriculture are applied as nanofertilizers and/or nanopesticides. Positive results have been observed in terms of plant growth when using nano-based agricultural amendments. However, their continuous application may have adverse effects on plant-associated rhizospheric and endospheric microorganisms which often play a crucial role in plant growth, nutrient uptake, and disease prevention. While research shows that the application of nanoparticles has the potential to improve plant growth and yield, their effect on the diversity and function of plant-associated microorganisms remains under-explored. This review provides an overview of plant-associated microorganisms and their functions. Additionally, it highlights the response of plant-associated microorganisms to nanoparticle application and provides insight into areas of research required to promote sustainable and precision agricultural practices that incorporate nanofertilizers and nanopesticides.

Did you know scientists can make tiny structures called nanoparticles, which are smaller than the smallest ants? Nanoparticles are useful for a lot of different things, including helping farmers grow our food crops. Without fertilizers, which are nutrients applied to gardens and farms to help crops grow, it would be difficult to grow enough vegetables and fruits to support all the humans on Earth. However, some fertilizers are too big to be easily taken up by plants. Because nanoparticles are so tiny, they can easily get into plants and help them grow. But there is a downside—sometimes nanoparticle fertilizers disturb the growth of natural organisms in the soil, such as bacteria. Some soil bacteria also help plants to grow, so they need to be protected. It is therefore important to understand how nanoparticle fertilizers affect the bacteria in the soil.

At psychrophilic temperatures (<20 °C), anaerobic digestion produces less methane (CH4). For psychrophilic anaerobic digestion (PAD) to be successful, investigation of cold-adapted microbial consortia involved in methane production is critical. This study aimed to investigate the microbial community driving enhanced methane production from the cold-adaptation process and bioaugmentation of PAD with cold-adapted inoculum (BI). Microbial consortia in cattle manure (CM) and food waste (FW) were adapted and applied during batch PAD of CM and FW to bioaugment methane production at 15 °C. Cold adaptation and PAD with BI resulted in cumulative specific methane yields of 0.874 ± 0.231 and 0.552 ± 0.089 L CH4 g−1 volatile solids, respectively, after 14 weeks, while the absence of BI (control) led to acidification and no methane production during PAD. Following 16S rRNA V4–V5 amplicon sequencing and metagenomic analyses, Methanosarcina was revealed as a key driver of methanogenesis during cold adaptation and PAD bioaugmentation. Furthermore, based on the predictive functional and metabolic analysis of the communities, possible synergies were proposed in terms of substrate production and utilization by the dominant microbial groups. For instance, during methane production, Bacteroides and Methanobrevibacter were possibly involved in a syntrophic relationship, which promoted methanogenesis by Methanosarcina. These findings provide insight into the prospective microbial synergies that can be harnessed and/or regulated in cold-adapted inoculum for the improvement of methane production during PAD.