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Fermentative kitchen waste to produce high-value chemicals (e.g., acetic acid) has been investigated actively in the past decades. Creating an alkaline condition is widely used to improve the hydrolysis of polysaccharide and inhibit the methanogenesis, but this method significantly increases the overall cost. Herein, the present study investigated the bioaugmentation with rumen fluid to improve acetic acid production from kitchen waste at neutral condition via strengthening hydrolytic and acid-forming bacteria. Results showed that the highest acetic acid yield reached 1.52 g/L at rumen fluid and granular sludge ratio of 1:1. The proportion of acetic acid in volatile fatty acids (VFAs) has increased by 10% compared to control. Microbial community analysis revealed that bioaugmentation with rumen fluid increased the relative abundance of Prevotella and Rikenellaceae_RC9_gut_group which has the ability to degrade polysaccharides and produce acetic acid. Moreover, the proliferation of butyric acid producers (Clostridium_sensu_stricto_1 and Clostridium_sensu_stricto_7) were inhibited significantly, which was in agreement with high acetic acid proportion in VFAs. The bioaugmentation strategy and process optimization provided an energy and cost-saving method for acetic acid production from kitchen waste. [ABSTRACT FROM AUTHOR]

Paracetamol is one of the most commonly used painkillers. Its significant production and consumption result in its presence in the environment. For that reason, paracetamol has a negative impact on the organisms living in ecosystems. Therefore, it is necessary to develop effective methods to remove paracetamol from sewage. One of the methods is the bioaugmentation of activated sludge with organisms with increased degradation potential in relation to paracetamol. This study determined the effectiveness of paracetamol degradation by activated sludge augmented with a free or immobilised Pseudomonas moorei KB4. To immobilise the strain, innovative capsules made of cellulose acetate were used, the structure of which provides an optimal environment for the development of bacteria. Augmentation with both a free and immobilised strain significantly improves the efficiency of paracetamol biodegradation by activated sludge. Over a period of 30 days, examined systems allowed ten doses of paracetamol decomposition, while the unaugmented system degraded only four. At the same time, using the immobilised strain does not significantly affect the functioning of the activated sludge, which was reflected in the stability of processes such as nitrification. Due to the high stability of the preparation, it can become a valuable tool in wastewater treatment processes. [ABSTRACT FROM AUTHOR]

Biopurification system (BPS) or biobeds are low-cost system for decontamination of on-farm generated pesticide waste. A biobed contains a mixture of soil, lignocellulosic biomass and organic matter source (compost/peat) and works on the principal of retention of pesticide in high organic matter matrix and its subsequent degradation by microbes. Bioaugmentation, a green technology, is defined as the improvement of the degradative capacity of biobeds by augmenting specific microorganisms. During last 20 years, several studies have evaluated pesticide degradation in biobeds augmented with bacterial and fungal species and prominent microorganism include genus Pseudomonas, Sphingomonas, Arthrobacter, Phanerochaete, Stereum, Delftia, Trametes, Streptomyces etc. Degradation of pesticides belonging to major classes have been studied in the bioaugmented biobeds. Studies suggested that some pesticides were degraded faster in the bioaugmented biobeds subject to survival and proliferation of degrading microbe. However, no effect of bioaugmentation was observed on degradation of some pesticides and no clear reason for the same was evident. Bioaugmentation with pesticide degrading microorganisms/consortium in combination with rhizosphere-assisted biodegradation could be an optimal strategy for accelerating the degradation of pesticides in biobeds. [ABSTRACT FROM AUTHOR]

The coexistence of various organic pollutants in soil always draws extensive attention because of their difficulties and complexity for remediation. Especially, the impacts of bioremediation on soil co-contaminated with benzene, toluene, and trichloroethylene (TCE) have seldom been comprehensively evaluated yet. In this study, the contributions of biostimulation, bioaugmentation, and their combination for the bioremediation of the co-contaminated soil containing benzene, toluene, and TCE were systematically investigated. The addition of nutrients ((NH4)2SO4 (as N source), K2HPO4 (as P source), vegetable oil and CH3COONa (as C sources)) enhanced the degradation efficiency of the co-contaminated soil by 10.19% to 49.62%. The optimal biostimulation condition involved using vegetable oil as the carbon source with a C: N: P ratio of 100: 10: 1. Meanwhile, the addition of the microbial cultures screened and domesticated from the co-contaminated soil, named B-T, effectively enhanced the removal rate of contaminants by 33.02% to 37.55%. The genera comprising Pseudomonas, Stenotrophomonas, and Chryseobacterium in B-T exhibited the highest relative abundance, suggesting their potential for the removal of benzene, toluene, and TCE. Besides, the coupling of biostimulation and bioaugmentation enhanced the degradation efficiency by 62.38% to 68.84%, showing the most effective biodegradation effects. The coupled strategy showed synergistic effects of both, increasing the quantity and activity of microorganisms and accelerating the biodegradation of target contaminants. The findings indicated that the coupling of bioaugmentation and biostimulation treatment strategy holds promise for the bioremediation of benzene, toluene, and TCE from co-contaminated soil. [ABSTRACT FROM AUTHOR]

Bioinoculants of Sphingobium indicum B90A have been used to decontaminate hexachlorocyclohexane (HCH)-contaminated soils in the past. There is no selective or convenient method available to track the added B90A in HCH-contaminated soils in the presence of several native sphingomonads. Here, we describe a method, BioMarkTrack, for tracking B90A bioinoculant by simple amplification of the B90A specific biomarker genes. Whole-genome sequence data of 120 different genera of sphingomonads (Sphingobium, Novosphingobium, Sphingomonas, Sphingopyxis, and Sphingosinicella) were retrieved from the NCBI database and annotated. Intra- and inter-genus similarity searches, including the genome of B90A as a reference was conducted. 122 unique gene sequences were identified in strain B90A, out of which 45 genes were selected that showed no similarity with the NCBI non-redundant (NR) database or gene sequences in the publicly available database. Primers were designed for amplification of 4 biomarkers. To validate the biomarkers B90A tracking efficacy in bioaugmented soils, a microcosm study was conducted in which sterile garden and HCH-contaminated dumpsite soils were amended with strain B90A. Amplification of the biomarker was observed both in sterile garden soil and HCH-contaminated dumpsite soil but not in control (lacking B90A) samples. Further, the primer set was used to track B90A in a bioremediation field trial soil, demonstrating the convenience and efficiency of the simple PCR-based method, which can be employed for tracking B90A in bioaugmented soils. The approach as presented here can be employed on different bioinoculants to identify unique biomarkers and then tracking these organisms during bioremediation. [ABSTRACT FROM AUTHOR]

Fuel, a petroleum derivative, contributes to soil pollution because of its hydrocarbons, which are difficult to decompose. Bioremediation can assist by introducing microbes that are capable of degrading hydrocarbons and enhancing this process by adding nutrients. This study validated previous research by adding the most optimum nutrients, bacteria with the right ratio, and pre-treatment of soil washing on the degradation value of hydrocarbons in crude oil-contaminated soil. Pre-treatment involved washing the soil with surfactant tween-80, determining the type of mixed bacterial culture variables, adding varying concentrations of inoculum and inorganic nutrients, and determining the optimal total petroleum hydrocarbon (TPH) reduction. The study found that the provision of nutrients, bacteria, and pre-treatment in soil washing had no significant effect on the original soil TPH.

To assess the possibility of using aerobic denitrification (AD) bacteria with high NO2−-N accumulation for nitrogen removal in wastewater treatment, conditional optimization, as well as sole and mixed nitrogen source tests involving AD bacterium, Comamonas sp. pw-6 was performed. The results showed that the optimal carbon source, pH, C/N ratio, rotational speed, and salinity for this strain were determined to be succinate, 7, 20, 160 rpm, and 0%, respectively. Further, this strain preferentially utilized NH4+-N, NO3−-N, and NO2−-N, and when NO3−-N was its sole nitrogen source, 92.28% of the NO3−-N (150 mg·L−1) was converted to NO2−-N. However, when NH4+-N and NO3−-N constituted the mixed nitrogen source, NO3−-N utilization by this strain was significantly lower (p < 0.05). Therefore, a strategy was proposed to combine pw-6 bacteria with traditional autotrophic nitrification to achieve the application of pw-6 bacteria in NH4+-N-containing wastewater treatment. Bioaugmented application experiments showed significantly higher NH4+-N removal (5.96 ± 0.94 mg·L−1·h−1) and lower NO3−-N accumulation (2.52 ± 0.18 mg·L−1·h−1) rates (p < 0.05) than those observed for the control test. Thus, AD bacteria with high NO2−-N accumulation can also be used for practical applications, providing a basis for expanding the selection range of AD strains for wastewater treatment. HIGHLIGHTS Optimal C source, pH, C/N ratio, and salinity for Comamonas sp. pw-6 were found.; Strain pw-6 preferentially utilized NH4+-N, NO3−-N, and NO2−-N, successively.; When NO3−-N was the sole nitrogen source, 92.28% of the NO3−-N converted to NO2−-N.; Addition of pw-6 into sequencing batch reactor can enhance NH4+-N and total inorganic nitrogen removal and reduce NO3−-N accumulation.;

In this work, the effect of bioaugmentation on the hydrolysis and acidogenesis efficiency of bedding straw mixed with maize silage is examined. A plug-flow bioreactor was operated for 70 weeks with maize silage as a reference feedstock and subsequently with an increasing straw content of 30% and 66% (w/w). Bioaugmentation with two Paenibacillus species was conducted at each process condition to investigate the impact on hydrolysis of the recalcitrant lignocellulosic feedstock. A stable acidogenic digestion of the substrates was achieved, during which acetic and butyric acid were accumulated as main byproducts. Specific hydrolysis rates between 258 and 264 gO2 kg−1VS were determined for pure maize silage and maize silage mixed with 30% of straw, while the specific hydrolysis rate decreased to 195 gO2 kg−1VS when a mixture with 66% of straw was applied. Bioaugmentation with Paenibacillus spp. increased the specific hydrolysis rate by up to 41–63% for pure maize silage and the mixture with 30% of straw, while no increase was observed with a mixture of 66% of straw. Acid production, however, was enhanced by 21 to 42% following bioaugmentation for all substrate mixtures. A positive effect on the physiological state of cultures, as recorded with frequency-dispersed polarizability, was seen after bioaugmentation, which remained for two retention times during the continuous fermentation mode. Recirculation of the thin sludge further prolonged the positive effects of bioaugmentation. The results of this work provide a basis to optimize the amount of the bioaugmented microorganisms and hydrolysis of biogenic material with respect to sustainable effects on process performance and costs. [ABSTRACT FROM AUTHOR]

Lubricant oils are largely responsible for environmental contamination and surfactants can hopefully improve the bioremediation process in soils contaminated with this kind of waste. However, to date only a few studies have elucidated how different surfactants affect the bioremediation process in oil-contaminated soils using the bioaugmentation technique. Thus, this study aimed to compare the effects of surfactants on the bioremediation process of waste lubricant oil in soil in association or not with bioaugmentation. Three biostimulating agents were tested: a chemical detergent, a synthetic surfactant, and a biosurfactant (rhamnolipid). The bioaugmentation process with Pseudomonas aeruginosa showed a faster biodegradation activity with total biodegradation on 181 day after application. The biosurfactant increased the number of microbial and fungal colonies leading to high biodegradation levels and a quicker treatment with or without the bioaugmentation. Bioaugmentation associated with biosurfactant reached 30.43 mg of CO2 of production on 181 day (90% of total biodegradation of waste lubricant oil) and reduced soil toxicity to 30%. Therefore, results showed that the association of biosurfactant and bioaugmentation with P. aeruginosa represents an ecologically viable strategy for bioremediation of soils contaminated with waste lubricant oil. [ABSTRACT FROM AUTHOR]

The feasibility of a simultaneous nitrification, denitrification and fermentation process (SNDF) under electric stirrer agitation conditions was verified in a single reactor. Enhanced activated sludge for phenol degradation and denitrification in pharmaceutical phenol-containing wastewater under low dissolved oxygen conditions, additional inoculation with Comamonas sp. BGH and optimisation of co-metabolites were investigated. At a hydraulic residence time (HRT) of 28 h, 15 mg/L of substrate as strain BGH co-metabolised substrate degraded 650 ± 50 mg/L phenol almost completely and was accompanied by an incremental increase in the quantity of strain BGH. Strain BGH showed enhanced phenol degradation. Under trisodium citrate co-metabolism, strain BGH combined with activated sludge treated phenol wastewater and degraded NO2−-N from 50 ± 5 to 0 mg/L in only 7 h. The removal efficiency of this group for phenol, chemical oxygen demand (COD) and TN was 99.67%, 90.25% and 98.71%, respectively, at an HRT of 32 h. The bioaugmentation effect not only promotes the degradation of pollutants, but also increases the abundance of dominant bacteria in activated sludge. Illumina MiSeq sequencing research showed that strain BGH promoted the growth of dominant genera (Acidaminobacter, Raineyella, Pseudarcobacter) and increased their relative abundance in the activated sludge system. These genera are resistant to toxicity and organic matter degradation. This paper provides some reference for the activated sludge to degrade high phenol pharmaceutical wastewater under the action of biological enhancement. [ABSTRACT FROM AUTHOR]

The total petroleum hydrocarbons (TPH) in used engine oil-polluted soil constrains its natural bioattenuation. Synergistic actions of biostimulation and bioaugmentation in microbial biodegradation mediated by the addition of keratinaceous materials resulted in the biodegradation of TPH. In this study, keratinous materials served as the source of organic nutrients to improve the soil's physicochemical properties and promote the proliferation of keratinolytic and hydrocarbonoclastic bacteria. After the biodegradation activity, the TPH declined from 48,865 mg kg−1 to a threshold lower than 10,000 mg kg−1 in 180 days except in the control groups. The TPH biodegradation efficiencies ranged between 70.5–91.5% in the treatment groups S1, S2 and S3 while natural bioattenuation in control groups S4 and S5 ranged between 18.5–22.5%. Biodegradation kinetics modelling indicated decay rates (0.0075 to 0.0137 per day) and half-life (50.38 to 91.29 days) in the treatment groups, while the control group recorded decay rates (0.0011 to 0.0014 per day) and half-life (487.29 to 616.74) days. From the culture-independent analysis to identify the keratinolytic and hydrocarbonoclastic bacteria in the soil, the changes in bacterial community structures bacterial dynamics, diversity, community structure and phylogenesis were determined. The keratinolytic and hydrocarbonoclastic bacteria identified were made up of Proteobacteria (52%), Actinobacteriota (22%), Firmicutes (4%), Planctomycetota (2%), Acidobacteriota (2%) and Chloroflexi (1%). The AlkB gene copies in the treatment groups increased from 6.25 × 105 to 1.25 × 107 copies ng DNA−1, while the control groups decreased from 6.20 × 105 copies ng DNA−1 to 6.05 × 104 copies ng DNA−1 in 180 days. [ABSTRACT FROM AUTHOR]

Dye is a substance that imparts colour onto textiles, fabrics, paper, leather, etc. and is not altered by washing, heating, and light. Dyes were extracted from plants, animals, and minerals until synthetic dyes came to the market, as synthetic dyes were more stable, readily available, and inexpensive. Despite being extremely important to the economy, they have been among the most significant global polluters. Textile dye industries have become the chief source of water pollution, with their effluents increasing the turbidity of water and reducing photosynthesis and dissolved oxygen levels. This leads to significant damage to aquatic biodiversity, threatening the survival of many species. Synthetic dyes have carcinogenic, mutagenic, and genotoxic effects on animals and human beings, posing a severe health risk. The degradation of dyes is essential for ensuring the sustainability of the environment for future generations. The traditional physicochemical means of dye treatment are not convenient because of the high solubility in water, cost of method utilisation and other disadvantages related to these techniques. To overcome the disadvantages of physicochemical treatment, biological methods or bioremediation can be used as an alternative. The objective of this review article is to study the mechanisms involved in the degradation of textile dyes by bacteria to obtain sustainable, economically and ecologically sound solutions for dye treatment. This paper will explain the various types of natural and synthetic dyes utilised in the textile industry, their chemistry, and how they affect water and soil ecosystems. The treatment of textile dye by various physicochemical methods and their advantages and disadvantages are also discussed. In bioremediation, the microorganisms utilize organic pollutants as a source of food or energy. Bioremediation uses biosorption and enzymatic activity for dye degradation, which does not disturb natural processes and is thus sustainable. The microorganisms secrete crucial extracellular and intracellular enzymes that carry out decolourisation and degradation through a series of events, which include hydrolysis, acidogenesis, and methanogenesis. We will discuss how aerobic and anaerobic microorganisms degrade these textile dyes through the process of biodegradation and bioaugmentation and how this technology provides a clean and eco-friendly method for removing textile dyes. [ABSTRACT FROM AUTHOR]

Single-use facial masks which are predominantly made out of polypropylene is being used and littered in large quantities during post COVID-19 situation. Extensive researches on bioremediation of plastic pollution on soil led to the identification of numerous plastic degrading microorganisms. These organisms assimilate plastic polymers as their carbon source for synthesizing energy. Pseudomonas fluorescens (PF) is one among such microorganism which is being identified to biodegrade plastic polymers in controlled environment. The natural biodegradation of facial mask in soil-like fraction collected from municipal waste management site, bioaugmentation of the degradation process with Pseudomonas fluorescens, biostimulation of the soil with carbonless nutritional supplements and combined bioaugmentation with biostimulation process were studied in the present work. The study has been conducted both in controlled and in natural condition for a period of 12 months. The efficiency of the degradation was verified through FTIR analyses using carbonyl index, bond energy change, Loss in ignition (LOI) measurement along with CHNS analyses of residual substances. The analysis of results reported that carbonyl index (in terms of transmittance) was reduced to 46% of the control batch through the inclusion of PF in natural condition. The bioaugmented batch maintained in natural condition showed 33% reduction of LOI with respect to the control batch. The unburnt carbon content of the residual matter obtained from the furnace were analysed using CHNS analyser and indicated the lowest carbon content in the same bioaugmented batch. In this study, an attempt is made to verify the feasibility of enhancing biodegradation of single-use facial mask by bioaugmentation of soil-like fraction available in solid waste management park with Pseudomonas fluorescens under natural condition. CHNS and FTIR analysis assures the biodegradation of plastic waste in the soil-like fraction using Pseudomonas fluorescens under both controlled and natural environmental condition. [ABSTRACT FROM AUTHOR]

The observation of photosynthetic biofilms growing on the Fine Residue Deposit (FRD) kimberlite produced by the Venetia Diamond Mine, Limpopo, South Africa suggests that processed kimberlite supports bacterial growth. The presence of this biofilm may aid in the acceleration of weathering of this ultra-mafic host material - a process that can sequester CO2 via carbon mineralization. Laboratory and field trial experiments were undertaken to understand the microbe-mineral interactions occurring in these systems, and how these interactions impact geochemical cycling and carbonate precipitation. At laboratory scale it was discovered that using kimberlite as a growth supplement increased biomass production (up to 25-fold) and promoted microbiome diversity, while the inoculation of FRD systems aided in the aggregation, settling, and dewatering of kimberlitic slurries. Field trial studies combining photosynthetic biofilms (cultured in 3 × 1,000 L bioreactors) with FRD material were initiated to better understand microbially enhanced mineral carbonation across different depths, and under field environmental conditions. Over the 15-month experiment the microbial populations shifted with the kimberlitic environmental pressure, with the control and inoculated systems converging. The natural endogenous biosphere (control) and the inoculum accelerated carbonate precipitation across the entire 40 cm bioreactor depth, producing average 15-month carbonation rates of 0.57 wt.% and 1.17 wt.%, respectively. This corresponds to an annual CO2e mine offset of ~4.48% and ~ 9.2%, respectively. Millimetre-centimetre scale secondary carbonate that formed in the inoculated bioreactors was determined to be biogenic in nature (i.e., possessing microbial fossils) and took the form of radiating colloform precipitates with the addition of new, mineralized colonies. Surficial conditions resulted in the largest production of secondary carbonate, consistent with a ca. 12% mine site CO2e annual offset after a 15-month incubation period. [ABSTRACT FROM AUTHOR]

BACKGROUND: Bacillus velezensis DQA21 is a functional strain used in the fermentation process of strong‐aroma baijiu; however, its specific role in the process is still unclear. RESULTS: In this study, specific roles of B. velezensis DQA21 in the fermentation process were explored. Bioaugmentation of B. velezensis DQA21 increased the diversity and abundance of the bacterial community during the first 32 days of fermentation and significantly inhibited the diversity and richness of the fungal community during days 12 to 32. According to cluster analysis, changes in the microbial community structure were observed during fermentation, and the fermentation process could be divided into two stages: stage I, days 0–12; and stage II, days 12–45. Additionally, the microbial community structures during the two fermentation stages were significantly different. Co‐occurrence analysis showed that bioaugmentation with Bacillus increased the correlation between microorganisms in jiupei and had a significant impact on the overall network structure of the microbial community. In addition, Bacillus significantly increased the production of flavor substances in jiupei, causing the total esters, total alcohols, and total acids contents to increase by 19.1%, 81.1%, and 25.9% respectively. CONCLUSION: The results suggested that bioaugmentation with B. velezensis DQA21 had a strong impact on the microbial community structure in strong‐aroma baijiu, enhancing the volatile flavor components. Additionally, the work also provides a better understanding on the effect of augmentation on the microbial community in jiupei, which could help better regulation of solid‐state fermentation in strong‐aroma baijiu. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Soil contamination by petroleum, including crude oil from various sources, is increasingly becoming a pressing global environmental concern, necessitating the exploration of innovative and sustainable remediation strategies. The present field-scale study developed a simple, cost-effective microbial remediation process for treating petroleum-contaminated soil. The soil treatment involves adding microbial activators to stimulate indigenous petroleum-degrading microorganisms, thereby enhancing the total petroleum hydrocarbons (TPH) degradation rate. The formulated microbial activator provided a growth-enhancing complex of nitrogen and phosphorus, trace elements, growth factors, biosurfactants, and soil pH regulators. The field trials, involving two 500 m3 soil samples with the initial TPH content of 5.01% and 2.15%, were reduced to 0.41% and 0.02% in 50 days, respectively, reaching the national standard for cultivated land category II. The treatment period was notably shorter than the commonly used composting and bioaugmentation methods (typically from 8 to 12 weeks). The results indicated that the activator could stimulate the functional microorganisms in the soil and reduce the phytotoxicity of the contaminated soil. After 40 days of treatment, the germination rate of rye seeds increased from 20 to 90%, indicating that the microbial activator could be effectively used for rapid on-site remediation of oil-contaminated soils. [ABSTRACT FROM AUTHOR]

Metribuzin (MB), a triazinone herbicide is extensively sprayed for weed control in agriculture, has been reported to contaminate soil, groundwater, and surface waters. In soil, MB residues can negatively affect not only the germination of subsequent crops but also disturb soil bacterial community. The present study describes the use of biochar as a carrier material to immobilize MB-degrading bacterial consortium, for remediation of MB-contaminated soil and restoration of soil bacterial community in soil microcosms. The bacterial consortium (MB3R) comprised four bacterial strains, i.e., Rhodococcus rhodochrous AQ1, Bacillus tequilensis AQ2, Bacillus aryabhattai AQ3, and Bacillus safensis AQ4. Significantly higher MB remediation was observed in soil augmented with bacterial consortium immobilized on biochar compared to the soil augmented with un-immobilized bacterial consortium. Immobilization of MB3R on biochar resulted in higher MB degradation rate (0.017 Kd−1 ) and reduced half-life (40 days) compared to 0.010 Kd−1 degradation rate and 68 day half-life in treatments where un-immobilized bacterial consortium was employed. It is worth mentioning that the MB degradation products metribuzin-desamino (DA), metribuzin-diketo (DK), and metribuzin desaminodiketo (DADK) were detected in the treatments where MB3R was inoculated either alone or in combination with biochar. MB contamination significantly altered the composition of soil bacteria. However, soil bacterial community was conserved in response to augmentation with MB3R immobilized on biochar. Immobilization of the bacterial consortium MB3R on biochar can potentially be exploited for remediation of MB-contaminated soil and protecting its microbiota. [ABSTRACT FROM AUTHOR]

Ever since the start of the Industrial Revolution, environmental pollution has significantly increased. The prominent cause of most diseases in humans, animals, and plants is the presence of toxic materials, pollutants, contaminants, and hazardous compounds released by industries. One of the major factors is the presence of heavy metals in the air, water bodies and soil. Heavy metals have biomagnification and bioaccumulation characteristics, making them hazardous for flora and fauna on a large scale. Recently, biological sources such as bacteria, fungi, algae, etc., have been used to bioabsorb these heavy metals. The microbial properties of these cell walls are utilized for effective and low-cost absorption of metals. Bioaugmentation, biosorption and biostimulation are effective strategies for reducing the toxicity of hazardous contaminants in the soil and facilitating bioremediation. The mechanism of biosorption is mainly based on ions and functional groups present in the microbes. Fungal species are advantageous over bacteria as they are easier to handle, cost-effective and, most importantly, non-pathogenic, making them ideal candidates for biosorption. This review provides a comprehensive overview of various microbial strains utilized in bioremediation. Further, the review highlights the application of nanotechnology and metabolic engineering approaches to improve the efficacy of Biosorption, Biostimulation and Bioaugmentation. It provides insights on the role of microbial nanoparticles in bioremediation and prospects in the forte of microbe-assisted bioremediation. [ABSTRACT FROM AUTHOR]

Biohydrogen production is a green method that utilizes organic materials in activated sludge as a substrate. The process involves microorganisms contracting the volume of the sludge content to produce hydrogen, CO2, CH4, and etc. However, the efficiency of this process is low. In this study, bioaugmentation was carried out by inoculating a 10% Escherichia coli suspension adapted in whey and activated sludge medium. The effects of parameters such as pH, temperature, and stirring, the concentration of whey as carbon source and nitrate as nitrogen source on hydrogen production were screened using the Plackett-Burman method with Minitab 21 software. Among the selected parameters, pH, temperature, concentration of whey and nitrate were found to be the most effective parameters in hydrogen production and were further optimized using Response surface methodology. Stirring wasn't statistically significant. The optimum conditions for hydrogen production were pH=5.4, temperature=39 °C, whey concentration=30 g/L, and nitrate concentration=3.6 g/L. Under these conditions with a 10% inoculation, the total volume of gas production was extended to 1.61 L per liters of activated sludge with 0.046 mole H2 per liters of activated sludge. Comparing the bioaugmentation method with other method showed that the total time of the process decreased by 8 hours. Additionally, hydrogen production started after 10 hours of incubation and reached its maximum value in 16 hours, resulting in a 59% increase in productivity in less than 16 hours. [ABSTRACT FROM AUTHOR]

Civilian and military nuclear programs of several nations over more than 70 years have led to significant quantities of heterogenous solid, organic, and aqueous radioactive wastes bearing actinides, fission products, and activation products. While many physicochemical treatments have been developed to remediate, decontaminate and reduce waste volumes, they can involve high costs (energy input, expensive sorbants, ion exchange resins, chemical reducing/precipitation agents) or can lead to further secondary waste forms. Microorganisms can directly influence radionuclide solubility, via sorption, accumulation, precipitation, redox, and volatilization pathways, thus offering a more sustainable approach to remediation or effluent treatments. Much work to date has focused on fundamentals or laboratory-scale remediation trials, but there is a paucity of information toward field-scale bioremediation and, to a lesser extent, toward biological liquid effluent treatments. From the few biostimulation studies that have been conducted at legacy weapon production/test sites and uranium mining and milling sites, some marked success via bioreduction and biomineralisation has been observed. However, rebounding of radionuclide mobility from (a)biotic scale-up factors are often encountered. Radionuclide, heavy metal, co-contaminant, and/or matrix effects provide more challenging conditions than traditional industrial wastewater systems, thus innovative solutions via indirect interactions with stable element biogeochemical cycles, natural or engineered cultures or communities of metal and irradiation tolerant strains and reactor design inspirations from existing metal wastewater technologies, are required. This review encompasses the current state of the art in radionuclide biogeochemistry fundamentals and bioremediation and establishes links toward transitioning these concepts toward future radioactive effluent treatments. [ABSTRACT FROM AUTHOR]

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Groundwater is the most important source for drinking water in The Netherlands. Groundwater quality is threatened by the presence of pesticides, and biodegradation is a natural process that can contribute to pesticide removal. Groundwater conditions are oligotrophic and thus biodegradation can be limited by the presence and development of microbial communities capable of biodegrading pesticides. For that reason, bioremediation technologies such as bioaugmentation (BA) can help to enhance pesticide biodegradation. We studied the effect of BA using enriched mixed inocula in two column bioreactors that simulate groundwater systems at naturally occurring redox conditions (iron and sulfate-reducing conditions). Columns were operated for around 800 days, and two BA inoculations (BA1 and BA2) were conducted in each column. Inocula were enriched from different wastewater treatment plants (WWTPs) under different redox-conditions. We observed a temporary effect of BA1, reaching 100% removal efficiency of the pesticide 2,4-D after 100 days in both columns. In the iron-reducing column, 2,4-D removal was in general higher than under sulfate-reducing conditions demonstrating the influence of redox conditions on overall biodegradation. We observed a temporary shift in microbial communities after BA1 that is relatable to the increase in 2,4-D removal efficiency. After BA2 under sulfate-reducing conditions, 2,4-D removal efficiency decreased, but no change in the column microbial communities was observed. The present study demonstrates that BA with a mixed inoculum can be a valuable technique for improving biodegradation in anoxic groundwater systems at different redox-conditions. [ABSTRACT FROM AUTHOR]

Preventing soil degradation is an important task of modern agrarian science. Preservation and increase in beneficial soil microflora are a precondition for satisfactory ecological functioning of soil and its fertility. The purpose of this study was to investigate the dynamics of beneficial soil microflora in winter wheat crops under the impact of mineral fertilisers and Agrobacterium radiobacter on the lands of the south of Ukraine. The study was conducted in threefold replication in the conditions of the Kherson region in 2016- 2020 in the experimental fields of the Institute of Climate-Smart Agriculture of the National Academy of Agrarian Sciences of Ukraine. The study used a systematic design, and the following factors were investigated: no fertiliser and Agrobacterium radiobacter; N120P90; N90P60 + Agrobacterium radiobacter; N120P90 + Agrobacterium radiobacter. The study on the microflora composition in the soil layer at 0-30 cm was carried out in the main stages of winter wheat growth and development through the inoculation of nutritious environment. Statistical analysis was performed using the methods of analysis of variance, correlation, and regression analysis. Dynamic changes in the soil biota composition under the influence of the studied factor were established. The slightest response to mineral fertilisers and bacterial preparation application was in ammonifying bacteria, while the strongest response was in cellulosedegrading microorganisms. The winter wheat harvesting revealed a decrease in the number of ammonifying bacteria in the soil, while the number of nitrifying and cellulose-degrading microflora increased significantly. Regression models for the prediction of the number of nitrifying bacteria and cellulose-degrading microorganisms, developed based on experimental data, have great accuracy (the error is 3.78% and 7.79%), and allow determining the adverse effect of phosphorus fertiliser on the microflora of dark-chestnut soil. The study has no analogues in Ukraine and expands theoretical knowledge about the influence of mineral fertilisers and bacterial preparation, containing Agrobacterium radiobacter, on the composition of beneficial microflora of the dark-chestnut soil

This research investigated the association of consortium endophyte bacteria from different hosts to enhance the performance of Vetiveria zizanioides in treating textile wastewater using Floating Treatment Wetlands (FTWs). The endophyte bacteria were isolated from the roots of three natural plants (Oryza sativa, Colocasia esculenta, and Alternanthera philoxeroides) contaminated by textile wastewater. The selected isolated endophyte bacteria were subjected to the four FTWs reactors containing the Vetiveria sp and ran for 30 days in a semi-batch system to evaluate their performance. FTWs reactors-augmented endophyte bacteria could reduce the COD, color, and heavy metals in textile wastewater. The highest removal efficiencies of COD (74%) and color (F4) were observed in FK2 (vegetated control) and F4 reactor, respectively. The addition of endophyte bacteria increased the heavy reductions of Pb (52%) and Cd (33%) in reactors of F3 and F4, respectively. This study exhibited that the consortium endophyte bacteria isolated from the contaminated plants could improve the FTWs reactor performance. Finally, they reduce the plant stresses in the contaminated wastewater by increasing the plant biomass in roots and shoots. These findings reveal that the consortium of natural endophyte bacteria from different hosts does not inhibit their function and association with the other host plant, but they contribute positive responses to plant growth and pollutant degradation.

AbstractConcentrations greater than 20 mg/L of chlorinated volatile organic compounds (cVOCs) including tetrachloroethene (PCE), trichloroethene (TCE), and cis-1,2-dichloroethene (cDCE) have been present in site groundwater for more than four decades. To promote a faster clean-up time, an in situ bioremediation approach was evaluated using In-Situ Microcosms® (ISMs) followed by a full-scale in situ bioremediation approach. The ISM study evaluated slow-release versus quick-release carbon substrates with and without bioaugmentation using the chlorinated ethene degrading culture, SDC-9™. After a three-month incubation period, the ISMs were retrieved. The ISMs amended with a carbon source with or without bioaugmentation displayed greater than a 93% reduction in TCE, which corresponded to an increase in cDCE in all the ISMs. The Dehalococcoides population and gene abundances associated with chlorinated ethene biodegradation (tceA, bvcA, vcrA) increased three orders of magnitude in the bioaugmented ISMs over the natural attenuation ISM and carbon source only amended ISMs. Additionally, the SDC-9™ and AquaBupH®, an enhanced emulsified oil substrate (EOS®) and buffer, amended ISM unit showed the highest level of vinyl chloride and similar level of ethene to the SDC-9™ and EHC®, a controlled-release, organo-iron substrate, ISM. However, the AquaBupH and SDC-9™ ISM displayed the highest level of acetate, demonstrating active fermentation processes. The results of the ISM study indicated that a combined approach of biostimulation along with bioaugmentation effectively promoted conditions conducive to reductive dechlorination. The full-scale in situ bioremediation system coupled biostimulation with bioaugmentation using SDC-9™ to successfully reduce chlorinated ethenes in groundwater. The slow-release carbon substrate, EOS-100® served as a sustained carbon source along with CoBupH (buffering agent similar to AquaBupH), facilitating the production of hydrogen, through volatile fatty acid fermentation. This led to the reduction of chlorinated ethenes over the subsequent three years, showcasing minimal rebound in contaminant levels. Two rounds of bioaugmentation notably increased the Dehalococcoides population, accelerating the biodegradation processes, which is setting up the site for monitored natural attenuation. This study shows that using ISMs to guide full-scale bioremediation design resulted in an effective cVOC biodegradation system that led to quicker and more sustainable clean-up. [ABSTRACT FROM AUTHOR]

The use of biofuels has grown in the last decades as a consequence of the direct environmental impacts of fossil fuel use. Elucidating structure, diversity, species interactions, and assembly mechanisms of microbiomes is crucial for understanding the influence of environmental disturbances. However, little is known about how contamination with biofuel/petrofuel blends alters the soil microbiome. Here, we studied the dynamics in the soil microbiome structure and composition of four field areas under long-term contamination with biofuel/fossil fuel blends (ethanol 10% and gasoline 90%—E10; ethanol 25% and gasoline 75%—E25; soybean biodiesel 20% and diesel 80%—B20) submitted to different bioremediation treatments along a temporal gradient. Soil microbiomes from biodiesel-polluted areas exhibited higher richness and diversity index values and more complex microbial communities than ethanol-polluted areas. Additionally, monitored natural attenuation B20-polluted areas were less affected by perturbations caused by bioremediation treatments. As a consequence, once biostimulation was applied, the degradation was slower compared with areas previously actively treated. In soils with low diversity and richness, the impact of bioremediation treatments on the microbiomes was greater, and as a result, the hydrocarbon degradation extent was higher. The network analysis showed that all abundant keystone taxa corresponded to well-known degraders, suggesting that the abundant species are core targets for biostimulation in soil remediation processes. Altogether, these findings showed that the knowledge gained through the study of microbiomes in contaminated areas may help design and conduct optimized bioremediation approaches, paving the way for future rationalized and efficient pollutant mitigation strategies. [ABSTRACT FROM AUTHOR]

AbstractEvery year, a huge amount of lethal compounds, such as synthetic dyes, pesticides, pharmaceuticals, hydrocarbons, etc. are mass produced worldwide, which negatively affect soil, air, and water quality. At present, pesticides are used very frequently to meet the requirements of modernized agriculture. The Food and Agriculture Organization of the United Nations (FAO) estimates that food production will increase by 80% by 2050 to keep up with the growing population, consequently pesticides will continue to play a role in agriculture. However, improper handling of these highly persistent chemicals leads to pollution of the environment and accumulation in food chain. These effects necessitate the development of technologies to eliminate or degrade these pollutants. Degradation of these compounds by physical and chemical processes is expensive and usually results in secondary compounds with higher toxicity. The biological strategies proposed for the degradation of these compounds are both cost-effective and eco-friendly. Microbes play an imperative role in the degradation of xenobiotic compounds that have toxic effects on the environment. This review on the fate of xenobiotic compounds in the environment presents cutting-edge insights and novel contributions in different fields. Microbial community dynamics in water bodies, genetic modification for enhanced pesticide degradation and the use of fungi for pharmaceutical removal, white-rot fungi’s versatile ligninolytic enzymes and biodegradation potential are highlighted. Here we emphasize the factors influencing bioremediation, such as microbial interactions and carbon catabolism repression, along with a nuanced view of challenges and limitations. Overall, this review provides a comprehensive perspective on the bioremediation strategies. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs), a type of organic pollutants that are known to be potentially harmful to living beings, continue to accumulate in the environment. Owing to anthropogenic activities such as industrial emissions, fossil fuel combustion, forest fires, etc. the level of PAHs in the environment is constantly on the rise. In this review, acute and chronic health effects of PAH pollution on human health have been discussed. The authors have also shed lights on characteristics and possible routes of PAH exposure. Various bioremediation techniques and environmental considerations for PAH decontamination have also been compiled. Furthermore, contemporary biological techniques used to increase the effectiveness of removing PAH contamination such as catabolic genes, enzymes and genetic engineering methods (GEMs) have also been discussed. Advancements in recent years with regards to bacterial PAH degradation with a special focus on metagenomics have also been featured. The present article focuses on the current state-of-the-art research on PAHs biodegradation and how current research could move forward. [ABSTRACT FROM AUTHOR]

Developing an optimal environmentally friendly bioremediation strategy for petroleum products is of high interest. This study investigated heavy fuel oil (HFO)-contaminated soil (4 and 6 g kg−1) remediation by individual and combined bioaugmentation-assisted phytoremediation with alfalfa (Medicago sativa L.) and with cold plasma (CP)-treated M. sativa. After 14 weeks of remediation, HFO removal efficiency was in the range between 61 and 80% depending on HFO concentration and remediation technique. Natural attenuation had the lowest HFO removal rate. As demonstrated by growth rate and biomass acquisition, M. sativa showed good tolerance to HFO contamination. Cultivation of M. sativa enhanced HFO degradation and soil quality improvement. Bioaugmentation-assisted phytoremediation was up to 18% more efficient in HFO removal through alleviated HFO stress to plants, stimulated plant growth, and biomass acquisition. Cold plasma seed treatment enhanced HFO removal by M. sativa at low HFO contamination and in combination with bioaugmentation it resulted in up to 14% better HFO removal compared to remediation with CP non-treated and non-bioaugmented M. sativa. Our results show that the combination of different remediation techniques is an effective soil rehabilitation strategy to remove HFO and improve soil quality. CP plant seed treatment could be a promising option in soil clean-up and valorization. [ABSTRACT FROM AUTHOR]

AbstractBioaugmentation of veterinary antibiotic (VA)-contaminated feces with VA-degrading bacteria, can reduce the VA-selective pressure on manure microorganisms toward antibiotic resistance during organic soil fertilization. We explored the efficiency of a Sphingomonas isolate, able to degrade tiamulin (TIA), as a bioaugmentation agent for removing TIA from pig manures fortified with TIA at two concentrations (5 and 50 µg g−1). Bioaugmentation efficiency was compared with stockpiling and anaerobic digestion. Bioaugmentation accelerated TIA dissipation (DT50 = 32.3 and 66.2 days) compared with anaerobic digestion (DT50 = 103 and 126.7 days) and stockpiling (DT50 = 95.38 and 113.8 days). Furthermore, we determined the impact of TIA on methane production and followed microbial succession during anaerobic digestion. The lower TIA concentration stimulated biomethanation, seemingly, through induction of the increase of Methanosarcina (from below detection at the TIA-free samples to 17.1% of relative abundance at the low in TIA content samples), commonly linked with aceticlastic biomethanation. Our findings highlight (i) the potential of bioaugmentation in treating VA-contaminated manures for mitigating the dispersal of VA residues in agricultural settings (ii) the high risk of contamination of agricultural soils by the use of TIA-contaminated manures that have been stockpiled or anaerobically digested before their use in agricultural settings. [ABSTRACT FROM AUTHOR]

The research aimed to determine the influence of endophytic fungi on tolerance, growth and phytoremediation ability of Prosopis juliflora in heavy metal–polluted landfill soil. A consortium of 13 fungal isolates as well as Prosopis juliflora Sw. DC was used to decontaminate heavy metal–polluted landfill soil. Enhanced plant growth (biomass and root and shoot lengths) and production of carotenoids, chlorophyll and amino acids l-phenylalanine and l-leucine that are known to enhance growth were found in the treated P. juliflora. Better accumulations of heavy metals were observed in fungi-treated P. juliflora over the untreated one. An upregulated activity of peroxidase, catalase and ascorbate peroxidase was recorded in fungi-treated P. juliflora. Additionally, other metabolites, such as glutathione, 3,5,7,2′,5′-pentahydroxyflavone, 5,2′-dihydroxyflavone and 5,7,2′,3′-tetrahydroxyflavone, and small peptides, which include Lys Gln Ile, Ser Arg Ala, Asp Arg Gly, Arg Ser Ser, His His Arg, Arg Thr Glu, Thr Arg Asp and Ser Pro Arg, were also detected. These provide defence supports to P. juliflora against toxic metals. Inoculating the plant with the fungi improved its growth, metal accumulation as well as tolerance against heavy metal toxicity. Such a combination can be used as an effective strategy for the bioremediation of metal-polluted soil. [ABSTRACT FROM AUTHOR]

The use of inoculum containing autochthonous compost microorganisms Bacillus subtilis, B. amyloliquefaciens, and Pseudomonas aeruginosa allowed us to enhance biodegradation of food waste during composting. The survival rate of the introduced microorganisms was verified by classical microbiological and molecular biological methods. The introduction extended the high-temperature stage by 4 days, prevented acidification of the medium, and increased organic matter degradation and moisture evaporation, resulting in a 51% reduction in waste weight in two weeks. Introduced P. aeruginosa appeared to play a key role at the initial stage and was not detected after the temperature increased to 60°C. [ABSTRACT FROM AUTHOR]

The immobilisation of bacteria on biochar has shown potential for enhanced remediation of petroleum hydrocarbon-contaminated soil. However, there is a lack of knowledge regarding the effect of bacterial immobilisation on biosolids-derived biochar for the remediation of diesel-contaminated soil. This current study aimed to assess the impact of the immobilisation of an autochthonous hydrocarbonoclastic bacteria, Ochrobacterium sp. (BIB) on biosolids-derived biochar for the remediation of diesel-contaminated soil. Additionally, the effect of fertiliser application on the efficacy of the BIB treatment was investigated. Biochar (BC) application alone led to significantly higher hydrocarbon removal than the control treatment at all sampling times (4887–11,589 mg/kg higher). When Ochrobacterium sp. was immobilised on biochar (BIB), the hydrocarbon removal was greater than BC by 5533 mg/kg and 1607 mg/kg at weeks 10 and 22, respectively. However, when BIB was co-applied with fertiliser (BIBF), hydrocarbon removal was lower than BIB alone by 6987–11,767 mg/kg. Quantitative PCR (q-PCR) analysis revealed that the gene related to Ochrobacterium sp. was higher in BIB than in the BC treatment, which likely contributed to higher hydrocarbon removal in the BIB treatment. The results of the q-PCR analysis for the presence of alkB genes and FTIR analysis suggest that the degradation of alkane contributed to hydrocarbon removal. The findings of this study demonstrate that bacterial immobilisation on biosolids-derived biochar is a promising technique for the remediation of diesel-contaminated soil. Future studies should focus on optimising the immobilisation process for enhanced hydrocarbon removal. [ABSTRACT FROM AUTHOR]

Industrial development and the associated generation of waste requires attention for their management, treatment, and reduction without further degrading the quality of life. Microbes and plant-based bioremediation approaches are some of the sustainable strategies for the biodegradation of harmful pollutants instead of chemical-based treatment. Bioaugmentation is one such approach where microbial strains with the ability to degrade the targeted pollutant are introduced in a polluted environment. Harnessing of microbes from various locations, especially from the site of contamination (indigenous microbes), followed by optimization of the strains, inoculum size, media, and genetic engineering of the microbes along with a combination of strategies such as bio stimulation, phytoremediation is being applied to increase the efficiency of bioaugmentation. Further, bioaugmentation is influenced by various factors such as temperature, the composition of the pollutant, and microbial inoculum which needs to be considered for maximum efficiency of the treatment process. It has numerous advantages such as low cost, sustainability, and easy handling of the contaminants however, the major limitation of bioaugmentation is to increase the survival rate of the microbes involved in remediation for a longer duration in such a highly toxic environment. The review discusses these various aspects of bioaugmentation in brief for its large-scale implementation to address the global issue of pollution and environment management. [ABSTRACT FROM AUTHOR]

Low temperature is one of the limiting factors for anaerobic digestion in cold regions. To improve the efficiency of anaerobic digestion for methane production in stationary reactors under low-temperature conditions, and to improve the structure of the microbial community for anaerobic digestion at low temperatures. We investigated the effects of different concentrations of exogenous Methanomicrobium (10, 20, 30%) and different volumes of carbon fiber carriers (0, 10, 20%) on gas production and microbial communities to improve the performance of low-temperature anaerobic digestion systems. The results show that the addition of 30% exogenous microorganisms and a 10% volume of carbon fiber carrier led to the highest daily (128.15 mL/g VS) and cumulative (576.62 mL/g VS) methane production. This treatment effectively reduced the concentrations of COD and organic acid, in addition to stabilizing the pH of the system. High-throughput sequencing analysis revealed that the dominant bacteria under these conditions were Acidobacteria and Firmicutes and the dominant archaea were Candidatus_Udaeobacter and Methanobacterium. While the abundance of microorganisms that metabolize organic acids was reduced, the functional abundance of hydrogenophilic methanogenic microorganisms was increased. Therefore, the synergistic effect of Methanomicrobium bioaugmentation with carbon fiber carriers can significantly improve the performance and efficiency of low-temperature anaerobic fermentation systems. [ABSTRACT FROM AUTHOR]

Introduction: Crop straw, a major by-product of agricultural production, is pivotal in maintaining soil health and preserving the ecological environment. While straw incorporation is widely recognized as a sustainable practice, the incomplete decomposition of crop residues poses challenges to plant growth, increasing the risk of pests and diseases. This necessitates a comprehensive investigation. Methods: The current study employs a 28-day pot experiment to simulate the degradation of rice straw in paddy soils. The impacts of bioaugmentation and biostimulation on lignocellulose degradation are systematically evaluated. Results: Results indicate a high lignocellulose degradation ability in paddy soil, with over 80% straw weight loss within 28 days. Bioaugmentation with a lignocellulolytic microbial consortium enhances straw degradation during the initial stage (0-14 days). In contrast, biostimulation with readily available nutrients leads to soil acidification, hindering straw degradation and reducing microbial diversity. Furthermore, pH emerges as a critical factor influencing microbial community stability and function during lignocellulose degradation. Microbial co-occurrence network analysis reveals thatmicroorganisms occupy ecological niches associated with different cellulose components. Notably, Module M2, comprising Proteobacteria, Firmicutes, Gemmatimonadota, Actinobacteriota, Bacteroidota, Myxococcota, Halobacterota, and Acidobacteriota, positively correlates with pH and weight loss. Discussion: This study significantly advances our understanding of microbial mechanisms in soil decomposition, emphasizing the pivotal role of pH in community stability and function in paddy soil. These findings can inform future strategies for managing rice straw while safeguarding soil ecosystem health. [ABSTRACT FROM AUTHOR]

Approximately 95% of urban solid waste worldwide is disposed of in landfills. About 14 million metric tonnes of this municipal solid waste are disposed of in landfills every year in Malaysia, illustrating the importance of landfills. Landfill leachate is a liquid that is generated when precipitation percolates through waste disposed of in a landfill. High concentrations of heavy metal(loid)s, organic matter that has been dissolved and/or suspended, and inorganic substances, including phosphorus, ammonium, and sulphate, are present in landfill leachate. Globally, there is an urgent need for efficient remediation strategies for leachate-metal-contaminated soils. The present study expatiates on the physicochemical conditions and heavy metal(loid)s' concentrations present in leachate samples obtained from four landfills in Malaysia, namely, Air Hitam Sanitary Landfill, Jeram Sanitary landfill, Bukit Beruntung landfill, and Taman Beringin Landfill, and explores bioaugmentation for the remediation of leachate-metal-contaminated soil. Leachate samples (replicates) were taken from all four landfills. Heavy metal(loids) in the collected leachate samples were quantified using inductively coupled plasma mass spectrometry. The microbial strains used for bioaugmentation were isolated from the soil sample collected from Taman Beringin Landfill. X-ray fluorescence spectrometry was used to analyze heavy metal(loid)s in the soil, prior to the isolation of microbes. The results of the present study show that the treatments inoculated with the isolated bacteria had greater potential for bioremediation than the control experiment. Of the nine isolated microbial strains, the treatment regimen involving only three strains (all Gram-positive bacteria) exhibited the highest removal efficiency for heavy metal(loid)s, as observed from most of the results. With regard to new findings, a significant outcome from the present study is that selectively blended microbial species are more effective in the remediation of leachate-metal-contaminated soil, in comparison to a treatment containing a higher number of microbial species and therefore increased diversity. Although the leachate and soil samples were collected from Malaysia, there is a global appeal for the bioremediation strategy applied in this study. [ABSTRACT FROM AUTHOR]

• The combination of GE P. putida and RS promoted As methylation and volatilization. • Bioaugmentation and BC+RS promoted As methylation but reduced its volatilization. • The highest As volatilization is the GE P. putida and RS without flooding. • The As methylation ability of GE P. putida was stronger under non-flooded conditions. • Methylated As, DOC and pH in porewater can preferably model the As volatilization. Arsenic (As) fate in paddy fields has been one of the most significant current issues due to the strong As accumulation potential of rice plants under flooded conditions. However, no attempt was done to explore As methylation and volatilization under non-flooded conditions. Herein, we investigated the effects of water management on As methylation and volatilization in three arsenic-contaminated soils enhanced by biostimulation with straw-derived organic matter and bioaugmentation with genetic engineered Pseudomonas putida KT2440 (GE P. putida). Under flooded conditions, the application of biochar (BC), rice straw (RS) and their combination (BC+RS) increased total As in porewater. However, these effects were greatly attenuated under non-flooded conditions. Compared with RS amendment alone, the combination of GE P. putida and RS further promoted the As methylation and volatilization, and the promotion percentage under non-flooded conditions were significantly higher than that under flooded conditions. The combined GE P. putida and RS showed the highest efficiency in As methylation (88 µg/L) and volatilization (415.4 µg/(kg·year)) in the non-flooded soil with moderate As contamination. Finally, stepwise multiple linear regression analysis presented that methylated As, DOC and pH in porewater were the most important factors contributing to As volatilization. Overall, our findings suggest that combination of bioaugmentation with GE P. putida and biostimulation with RS/BC+RS is a potential strategy for bioremediation of arsenic-contaminated soils by enhancing As methylation and volatilization under non-flooded conditions. [Display omitted] [ABSTRACT FROM AUTHOR]