Hexavalent chromium [Cr(VI)], a highly toxic and carcinogenic pollutant prevalent in industrial effluents, poses severe environmental and health risks owing to its high solubility, mobility, and strong oxidizing properties. Cr(VI) contamination in drinking water can lead to severe health consequences. Secondary minerals, characterized by large specific surface areas, abundant surface functional groups, and high adsorption affinity, are promising candidates for decontaminating heavy metals in water. Herein, secondary ferric hydroxyl sulfate minerals were biosynthesized via microbial iron oxidation using Leptospirillum ferrodiazotrophum, a strain with high activity in oxidizing ferrous iron during mineralization. The goal was to explore the potential of developing a novel, environmentally friendly adsorbent for the effective immobilization of Cr(VI) from aqueous systems. Single-factor experiments were conducted to investigate the effects of pH, initial Cr(VI) concentration, adsorbent dosage, temperature, and rotational speed on adsorption performance. 85.09% Cr(VI) removal at 2 mg/L, with maximal uptake of 12.77 mg/g at 50 mg/L. Adsorption kinetics followed the pseudo-second-order model, suggesting that chemical adsorption may play a significant role in the process. Isotherm data fitted well with the Freundlich model, indicating adsorption on heterogeneous surfaces with non-uniform energy distribution. Thermodynamic analyses confirmed that the adsorption was exothermic and spontaneous at all tested temperatures. Post-adsorption characterization revealed changes in chromium valence and mineral phase transformations, confirming the successful immobilization of chromium. Additionally, hydroxyl, sulfate, and amino groups were identified as key binding sites. Further tests in complex simulated wastewater achieved 89.7% Cr(VI) removal, highlighting the adsorbent's potential for environmental remediation in acidic aqueous systems. This study provides a scientific foundation for the application of microbially synthesized secondary minerals in real-world remediation of chromium-contaminated water.
Agricultural soils are a primary sink for phthalate esters (PAEs), yet how tillage systems influence their fate and health risks remains unclear. This study investigated the effects of long-term tillage practices on PAE contamination by analyzing 52 paired soil samples from paddy and dryland fields in the Mid-Yangtze River Basin. Samples were analyzed via HPLC (limits of detection: 0.029–0.103 mg/kg; recoveries: 75.28%–104.24%). Source apportionment was explored using EPA PMF 5.0. The results revealed that tillage systems were associated with significantly different accumulation and compositional profiles of PAEs. Paddy soils had total PAE concentrations (mean 175.50 mg/kg) approximately 3.5-fold higher than adjacent drylands. This disparity was driven by di(2-ethylhexyl) phthalate (DEHP) (89.3% in paddies vs. 42.2% in drylands), potentially associated with anaerobic and ponded conditions. PMF tentatively identified agricultural plastics (>60%) as the primary DEHP source in paddies, while drylands showed diversified inputs. Using literature-derived bioaccumulation factors, health risk assessments revealed dietary intake as the dominant pathway (accounting for ∼99% of total exposure). DEHP was the sole risk driver, with dietary hazard quotients (adults: 7.35, children: 11.28) and carcinogenic risks (CR > 10−3) far exceeding safe thresholds (1.0 and 10−6, respectively), underscoring children's higher vulnerability. These findings indicate that agricultural management is strongly associated with specific organic pollution patterns, and mitigation should target DEHP inputs to safeguard food security.
Bioremediation of organically contaminated soil has attracted increasing attention as a sustainable remediation strategy, yet its practical efficiency remains constrained by the low bioavailability of hydrophobic pollutants and the limited stability of biocatalysts. Biochar-immobilized laccase for benzo[a]pyrene (BaP) removal remains limited by insufficient laccase stability and immobilization capacity arising from the heterogeneous, non-targeted surface functionalities of pristine biochar. Here, guanidinium-functionalized biochar was fabricated via arginine modification to enhance laccase immobilization and BaP removal in soil. Guanidinium functionalization regulated surface functionality and the interfacial charge environment, strengthened enzyme–support interactions, and facilitated electron transfer. Under the optimized conditions, L_Arg_BC achieved a protein immobilization efficiency of 88.55% and an enzyme activity recovery of 57.75%. The immobilized laccase exhibited improved thermal stability (>70.1% relative activity at 70 °C), pH stability (>80% relative activity at pH 3–5), and reusability (∼50% residual activity after six cycles). After 30 days, soil BaP removal was 1.83-fold higher than that achieved by free laccase, while the enzyme-associated transformation contribution in the aqueous system was estimated to be 41.17%. Microbial analysis showed enrichment of indigenous taxa potentially associated with subsequent PAH transformation, including Lysinibacillus and Aspergillus. This study provides a targeted biochar functionalization strategy for constructing stable immobilized-enzyme systems for hydrophobic organic pollutant remediation.
Polycyclic aromatic hydrocarbons (PAHs) pose a major challenge for soil remediation owing to their structural recalcitrance, and conventional bioremediation is often ineffective against high-molecular-weight PAHs (HMW-PAHs). In this study, two lignin-based slow-release biostimulant strategies were compared for the remediation of PAH-contaminated soil collected from a coking site over 120 days: physically encapsulated materials, including lignin-biochar (SRB) and lignin-resin (SRR) coated fertilizers, and a chemically synthesized aminated lignin material (CSK). All biostimulants were applied at an equivalent lignin input of 1% of soil dry weight. These biostimulants were designed to enhance PAH degradation by regulating nutrient availability and stimulating PAH-degrading microbial communities, while lignin may additionally contribute substrates associated with co-metabolic processes. The materials were characterized by SEM, FTIR, XPS, TGA/DSC, 1H NMR, and elemental analysis, confirming their distinct structural features and successful modification. Nutrient-release assays showed that the physically encapsulated materials released 26.2% and 24.4% of their total nitrogen by day 5 for SRB and SRR, respectively, followed by continued release to 61.5% and 57.8% by day 25. In contrast, CSK exhibited the strongest slow-release capacity, with cumulative nitrogen release of 11.2% by day 5 and 46.1% by day 25, but maintained a consistently lower release amplitude. The physically encapsulated materials showed superior remediation performance, achieving ΣPAHs removal rates of 76.0% for SRB and 74.4% for SRR, compared with 66.0% for CSK. They were particularly effective against HMW-PAHs, with removal rates of 65.8% and 57.1%, respectively, compared with 47.7% for CSK. The physically encapsulated treatments maintained relatively high and sustained available nitrogen concentrations, with coefficients of variation of 0.16-0.17. Available nitrogen concentrations were strongly positively correlated with residual ΣPAH, MMW-PAH, and HMW-PAH concentrations (r = 0.8-0.9). Despite its greater material stability and slow-release capacity, CSK released only 11.2% of its total nitrogen by day 5 and 46.1% by day 25 and maintained relatively small temporal variation in soil available nitrogen (CV ≈ 0.04); this nutrient-supply pattern was associated with lower PAH degradation, particularly for HMW-PAHs. These results indicate that the magnitude and temporal pattern of nitrogen supply, rather than release stability alone, are important factors associated with biostimulation efficacy. Microbial analysis showed that the physically encapsulated materials increased bacterial α-diversity and enriched PAH-degrading genera such as Mycobacterium, which was significantly correlated with PAH removal. Co-occurrence network analysis further indicated that SRR promoted positive bacteria-bacteria interactions (39.2%) while maintaining low cross-domain antagonism (6.3%). Overall, under the tested conditions, the physically coated lignin-based slow-release formulations evaluated here provided an effective strategy for the targeted remediation of PAH-contaminated soils, particularly those containing substantial HMW-PAH fractions, with their performance supported by coordinated nutrient-release and microbial-community responses.
Imaging Pulse-Amplitude-Modulation Fluorometry (PAM-F) is a quantitative, sensitive, and non-destructive tool for detecting early biofilm establishment, yet its broader use has been limited by the lack of standardised protocols and by uncertainties arising from material-specific effects. In this study, the first comprehensive protocol is presented considering substrate properties and achieving reproducible dark fluorescence yield (F0) measurements even for low algal cell densities. Our workflow combines standardised sample preparation with an algorithm-driven evaluation to generate calibration curves, detection limits, and optimal device settings. By applying two defined inoculation ranges of the subaerial green alga Jaagichlorella sp. AB13.021D5 to marble and concrete pellets, and polycarbonate membranes, we show that F0 intensity reflects not only algal abundance and device settings but also physical and mineralogical substrate properties. Particularly the high reflectance of marble increased noise and oversaturation effects, demonstrating the necessity of substrate-specific calibration. This transferable protocol establishes Jaagichlorella sp. AB13.021D5 as a test organism for comparative and application-oriented bioreceptivity studies (such as evaluating material susceptibility, comparing protective treatments, and monitoring early colonisation). By delivering validated measurement settings as well as substrate-specific calibration curves and detection limits for Imaging PAM-F studies, this work closes a critical methodological gap and supports the development of evidence-based biodeterioration management strategies.
The widespread contamination of polyvinyl chloride microplastics (PVC-MPs) poses significant environmental risks due to their recalcitrance and high chlorine content. Reductive dechlorination is critical for PVC aging, yet the role of electroactive bacteria (known to reduce various chlorinated compounds) in this process remains largely unexplored. Here, we investigated the potential of model electroactive bacterium Shewanella oneidensis MR-1 to mediate the reductive aging of PVC-MPs under anaerobic conditions. Our results demonstrated that S. oneidensis MR-1 mediated the reductive dechlorination of PVC-MPs, as evidenced by a 30.0% reduction in the Cl/C atomic ratio, a 21.2% decrease in the C-Cl/CH2 peak height ratio, and a 29.3% loss of C–Cl bonds with concomitant formation of C=C bonds. This aging process required an intact extracellular electron transfer (EET) pathway via the CymA-MtrABC-OmcA complex, as it was abolished by knockout of cymA or mtrABC-omcA. Density functional theory calculations and Fukui indices identified the terminal chlorine atom as the preferential site for electron attack. Based on these results, we propose a reductive aging pathway in which EET-delivered electrons cleave C–Cl bonds, leading to chain scission and unsaturation. This EET-based mechanism suggests a previously overlooked attenuation route for chlorinated microplastics in anoxic environments and provides a basis for potential bioremediation applications.
Unwanted graffiti made by spray paints are one of the most severe environmental pollutants that affect historical and modern buildings. Microorganisms offer a powerful, safe, eco-friendly, sustainable and low-cost biobased solution to remove graffiti from urban surfaces compared to conventional chemical and physical methods. However, a fully satisfying biocleaning procedure for the removal of spray paint has not yet been achieved due to the complexity of the paint composition, together with the fact that most of microorganisms found on paint films are airborne contaminants rather than active degraders. Spray paints contain xenobiotic compounds, creating an extreme environment for most microbial life. In this research a lab-scale biofilm enrichment strategy was developed to retrieve bacteria suitable for biocleaning purposes from spray paint in cans. Results indicated that this selective strategy i) effectively enriched non-endospore-forming bacteria suited to survive the harsh physicochemical conditions of canned paint; ii) established stable subaerial biofilms on painted surfaces, as demonstrated by metagenomic analysis using Illumina next generation sequencing technology; iii) utilised paint components as the sole carbon and energy source; and iv) remained amenable to large-scale, low-cost production for potential biocleaning applications. The most abundant taxon in both black and silver paints was isolated, sequenced using standard methods and identified as Klebsiella aerogenes.
Aluminium (Al3+) toxicity is a major constraint to soil health and plant productivity in bauxite rich acidic soils, where soluble Al3+ dominates soil solution chemistry. While bacterial biosorption has been proposed as a remediation approach, maximum experiments fail to differentiate exact biological Al3+ elimination from abiotic hydrolysis and precipitation, leading to overestimation of biosorption ability. This study reports this methodological gap by isolating an Al3+ tolerant bacterium and clearly measuring net bacterially mediated Al3+ biosorption after modifying for abiotic elimination using parallel cell free controls. A bacterial strain, T5, recognized as Bacillus licheniformis (Gen Bank accession PZ384576), was isolated from acidic bauxite associated soil (pH 4.7) where Al3+ constituted >85% of dissolved aluminium. Amongst four isolates, T5 exhibited the maximum aluminium tolerance (minimum inhibitory concentration >200 mg/L AlCl3) while retaining catalase, cytochrome c oxidase, and amylase activities under aluminium stress. Abiotic controls accounted for 35.6–54.9% of total Al3+ removal, whereas net bacterially mediated removal ranged from 12.6% to 32.6%, with maximum removal at 150 mg/L AlCl3. Biosorption kinetics and equilibrium were best described by the pseudo-second-order model (R2 = 0.989; qe = 21.8 mg/g) and the Langmuir isotherm (qmax = 21.8 mg/g; Rl = 0.23), indicating monolayer chemisorption. FTIR analysis revealed the involvement of hydroxyl, amide, carboxylate, and phosphate groups in Al3+ binding through surface complexation. By clearly separating abiotic and biological aluminium elimination, this experiment provides a more correct estimate of microbial biosorption ability and identifies Bacillus licheniformis T5 as a promising candidate for aluminium remediation, warranting further validation under soil microcosm and field conditions.
PLA degradation at the low temperatures of the marine environment is highly limited, whereas thermoplastic starch (TPS) can be blended with this polymer to modulate its properties and promote biodegradation. In this study, the effect of PLA‒TPS blending at different ratios (1:4, 1:1, 4:1, and 1:0) on the film's properties and biodegradation/disintegration behavior under laboratory conditions simulating the pelagic zone was analyzed. Films were prepared by melt‒blending and compression molding, and their mechanical, barrier, optical, and thermal properties were characterized. Biodegradation was evaluated by respirometric analyses following ISO 23977-1, and disintegration was monitored through the weight‒loss, while changes in microstructure, thermal behavior, and molecular size distribution of the residual film were also characterized. The properties of PLA‒TPS blend films were mainly affected by the properties of the matrix continuous phase (TPS, at low PLA ratio, and vice versa). Mechanical resistance, elastic modulus, oxygen permeability, and water vapor barrier capacity decreased in the blend films as the TPS ratio rose (58, 19, 35, and 600%, respectively, at the lowest starch ratio). The increase in the TPS ratio improved the biodegradation and disintegration of the blends. Biodegradation of the film's small particles after 160 exposure days ranged from 69% in neat PLA to 100% in samples with PLA‒TPS ratios of 1:4 and 1:1. However, disintegration percentages of larger film samples ranged from 0 (for neat PLA) to 59% (for the blend of 1:4 ratio). Degradation and water solubilization of the TPS fraction generated internal pores that increased the films' internal surface area, facilitating water access to the PLA phase and promoting PLA hydrolysis and subsequent bio-assimilation of monomers. Conversely, starch degradation was delayed by polymer retrogradation/recrystallisation and by the encapsulating effect of PLA, which prevented starch from being exposed to the aqueous medium and microbial action.
Copper corrosion in acidic environments remains a significant challenge in industrial applications, and the development of efficient, environmentally friendly corrosion inhibitors is highly desirable. In this study, the corrosion inhibition performance of Acer palmatum Thunb. leaf extract (APE) for copper in 0.5 M H2SO4 solution was investigated using electrochemical measurements, and surface characterisation, while phytochemical analysis and theoretical calculations were employed to elucidate the inhibition mechanism. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements demonstrated that APE exhibited excellent inhibition performance, achieving maximum inhibition efficiencies of 96.6% and 96.9%, respectively, at an optimum concentration of 700 mg/L at 298 K. Surface characterisation by scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM/EDS) revealed the formation of a protective adsorption layer on the copper surface after APE treatment. X-ray photoelectron spectroscopy (XPS) analysis further confirmed the interaction between the functional groups of APE constituents and the copper substrate, indicating chemical adsorption in the protective film formation. Ultra-performance liquid chromatography-quadrupole-time-of-flight mass spectrometry (UPLC-Q-TOF-MS) identified the major phytochemicals present in APE. At the same time, molecular dynamics (MD) simulations demonstrated the spontaneous adsorption of these active compounds onto the copper surface. The findings provide molecular-level insights into the corrosion-inhibition mechanism of APE and highlight its potential as a sustainable, effective green corrosion inhibitor for copper protection in acidic media.
Stone buildings exposed to outdoor environments deteriorate through coupled interactions among substrate properties, exposure conditions, and surface-associated microbiota. However, how these interactions translate into site-specific weathering pathways in sandstone historical buildings remains insufficiently resolved. Weathered sandstone surfaces from three historical buildings in Leshan, China, spanning nearly two millennia of building history, were examined using an integrated multi-proxy framework that combined microbial, geochemical, mineralogical, and microscale surface analysis. The results revealed a clear divergence in deterioration trajectories under identical regional climatic conditions. The Leshan Confucian Temple was characterized by strong C–N enrichment, abundant calcium oxalate, and biodeteriorated biofilm coatings, consistent with a biogenic weathering pathway. By contrast, the Salt Merchant's Mansion showed weak carbon accumulation, disrupted C–N coupling, sulfur and chloride enrichment, and substantial clay–evaporite environment, indicating a physicochemical pathway dominated by salt attack and external environmental inputs. Yanggong Que displayed intermediate characteristics, with overlapping signatures of both processes, together with mixed mineral assemblages and transitional microscale surface facies between biofilm-dominated and salt/Ca-enriched alteration states. Microbial communities showed modest location-associated structuring superimposed on a shared stress-tolerant regional core dominated by Cyanobacteria, Actinobacteriota, and Rubrobacter-related lineages. Functional inference and guild screening further indicated predicted potential for organic-acid production and nitrogen cycling, whereas sulfur-cycling signals remained comparatively limited. Overall, the findings indicate that deterioration of sandstone in historical buildings is governed by exposure-mediated divergence rather than a single uniform process. This comparative framework provides a basis for mechanistic diagnosis of surface decay and for more targeted conservation strategies.
Organotin compounds (OTCs) are persistent and ecotoxic pollutants that continue to pose environmental and health risks despite decades of regulatory restrictions. Although numerous remediation technologies have been developed, existing reviews have primarily provided descriptive accounts of individual methods, with limited critical comparison regarding their true detoxification efficacy, practical scalability, or inherent limitations. In this review, we critically examine different technology classes—advanced oxidation processes, adsorption, coagulation-flocculation, bioremediation, and phytoremediation. Key findings reveal that most studies report “removal efficiency” without confirming detoxification or mineralization, and the majority of investigations remain at laboratory scale using simplified matrices, leaving significant knowledge gaps regarding field applicability, transformation product toxicity, and life-cycle trade-offs. We also highlight that integrated treatment trains represent a promising but underexplored direction. To bridge the gap between laboratory innovation and field application, this review concludes by identifying five prioritized research needs: establishing standardized performance metrics beyond removal efficiency (including mineralization and toxicity endpoints), prioritizing transformation product identification, conducting matrix-specific and site-realistic validation, demonstrating pilot- and full-scale feasibility, and integrating life-cycle assessment with regulatory benchmarking. By shifting the focus from “what can be removed” to “what is genuinely remediated,” this review aims to provide a critical reference for researchers and practitioners working on OTC-contaminated sites.
The Tianlongshan Grottoes, a Buddhist cave complex carved into Permian sandstone in northern China between the sixth and tenth centuries, are increasingly threatened by surface microbial colonisation, yet the ecology of their stone-dwelling microbiota remains largely unexplored. We collected 24 sandstone samples from six representative caves spanning the Northern Qi and Tang dynasties and used 16S rRNA (V3–V4) and ITS1 amplicon sequencing to characterize bacterial and fungal communities. Co-occurrence network analysis, an iCAMP-style βNTI/RCbary framework, and FAPROTAX/FUNGuild functional prediction were applied to four ecological types: abundant, rare, generalist, and intermediate taxa. Bacterial communities, dominated by Actinobacteria and Proteobacteria, were assembled predominantly through deterministic homogeneous selection (69.4%), whereas fungal communities, mainly Ascomycota, were governed by stochastic ecological drift (88.9%). Rare taxa occupied disproportionately central positions in both co-occurrence networks, suggesting that they may represent structurally important components of the microbial communities, although their ecological functions remain to be experimentally validated. Predicted functional profiles varied among caves: Tang-period caves exhibited relatively coherent predicted bacterial functional profiles associated with taxa linked to photoautotrophy, nitrogen fixation, and aromatic compound degradation, alongside more complex fungal trophic combinations, whereas the Northern Qi cave (E1) showed a comparatively simpler profile and the dual-period cave (W16) displayed intermediate fungal characteristics. Because all functional inferences were based on taxonomic prediction rather than direct measurement, these findings should be interpreted as exploratory. Overall, our findings suggest that variation in microbial community assembly and predicted functional profiles on sandstone surfaces may reflect long-term ecological heterogeneity among caves. However, because environmental drivers and microbial functions were not directly measured, these interpretations should be regarded as ecological hypotheses requiring further validation. Nevertheless, this study provides an ecological framework for future conservation-oriented investigations of stone heritage microbiomes.
Emerging contaminants are often discharged into natural aquatic environments in the effluents from wastewater treatment plants, because conventional wastewater treatment is ineffective for eliminating them, even when biochemical oxygen demand and nutrients are well removed. In this work, we investigated the co-removals of benzophenone-3 (BP-3) and ammonium (NH4+) through bioaugmentation of Rhodococcus ruber F1 (R. ruber F1). Experimental results documented that NH4+–N and BP-3 could be removed simultaneously only when R. ruber F1 was added to the nitrifying biomass, which was able to oxidize NH4+, but not BP-3. Because BP-3 biodegradation was initiated by monooxygenation reactions that required O2, R. ruber F1 required dissolved O2 to biodegrade BP-3. After R. ruber F1 bioaugmentation, the kinetics of BP-3 were accelerated from zero to an average of 2.24 mg/(L·h), and BP-3 was removed completely over 3 h. Genome sequencing showed that R. ruber F1 contained genes for monooxygenases, demethylases, and dehydrogenase able to initiate BP-3 biodegradation, but these genes were not present in the acclimated nitrifying biomass. The results point how bioaugmentation can be a good strategy to expand the capacity of conventional biological processes to remove emerging contaminants and ammonium simultaneously. This is the first study to show that bioaugmentation achieved simultaneous BP-3 and ammonium removals.
Microbially induced calcium carbonate precipitation (MICCP) is a promising approach for enhancing the strength and durability of construction materials. This study explored the potential of fungal-based surface coatings for mortar specimens and its curing treatment to sustainably improve strength and durability properties by promoting CaCO3 precipitation in the mortar matrix. Fungal strains were isolated from the concrete walls of a building, among them three fungi (CF1, CF2, and CF3) exhibited urease activity. The fungal isolate CF3 exhibited higher urease activity (250 U/mL) and CaCO3 precipitation (180 mg/100 mL), which was further identified as Trichoderma harzianum. Sand consolidation experiments confirmed that CF3 effectively bound sand particles through extensive hyphal networks and CaCO3 precipitation. Fungal treatment on mortar specimens improved the compressive strength by 19.2% and reduced water sorptivity (0.0012) compared to its control (0.0057). The lower sorptivity values in fungal-treated specimens indicate improved densification and reduced porosity due to CaCO3 precipitation. SEM and EDS analysis confirmed the presence of CaCO3 crystals intertwined with fungal hyphae in the fungal treated mortar matrix. These findings establish T. harzianum (CF3) as a viable candidate for fungal-mediated calcite precipitation in cementitious materials, offering an alternative to bacterial systems for self-healing and durability enhancement.
Lichens function as multi-kingdom biofilm systems that actively drive mineral transformation on stone substrates. In this study, eight lichen species collected from Eastern Anatolia (Türkiye) were analyzed to characterize their associated microbial communities and the underlying biochemical mechanisms of stone biodeterioration. From an initial pool of 185 microbial isolates, a representative subset of 55 taxa was molecularly identified, revealing a diverse consortium dominated by Bacillus, Pseudomonas, Fusarium, Aspergillus, and the cyanobacterium Microcystis aeruginosa. The detection of M. aeruginosa, a microbe typically found in freshwater environments, within terrestrial lichen thalli demonstrates pronounced ecological plasticity and identifies lichens as transitional microhabitats between aquatic and lithic environments. The process of biodeterioration is driven by a combination of organic acid production and the presence of extracellular polymeric substances (EPS), which together generate localized acidic microenvironments (pH values as low as 4.8). In particular, oxalic acid was found to mediate a stoichiometrically defined transformation of calcium carbonate according to the following reaction:Quantitative analysis via HPLC and ICP-MS confirmed a direct correlation between microbial acid titers and massive elemental mobilization (up to 19,958 ppm Ca). This mass-balanced pathway directly links microbial metabolism to mineral phase transformation and provides a mechanistic framework for understanding lichen-induced stone decay. The integration of microbial ecology with stoichiometric mineral transformation has advanced current understanding of biogeochemical weathering in cultural heritage materials.
Cadmium (Cd) contamination of agricultural soils threatens food safety, and remediation is constrained by cost, secondary pollution, and damage to soil structure. Microbially induced carbonate precipitation (MICP) by ureolytic bacteria offers a low-energy alternative, but supplies no nutrients, and recent attempts to couple it with engineered amendments such as biochar have been confined to beaker incubations without an edible-crop endpoint. We tested whether three chemically distinct post-consumer organic wastes: coffee waste (CW), tea waste (TW), and plant residues (PR) applied at 5–25% (w/w) would differentially modulate MICP by Lysinibacillus fusiformis and reduce Cd phytoavailability to lettuce (Lactuca sativa). Soils were spiked at 25 mg kg−1 Cd and incubated for 56 days in triplicate (n = 3). The 20% TW treatment gave the strongest combined response: urease activity rose 480.0%, exchangeable Cd fell 67.5% with carbonate-bound Cd rising 256.9%, and root and leaf Cd fell 72.8% and 62.1%. The 25% CW treatment shifted Cd into less-labile fractions (exchangeable Cd −55.6%) yet reduced lettuce fresh weight by 91%, establishing an application-rate ceiling absent in TW and PR. This phytotoxicity was not attributable to phenolic content, which was higher in TW than CW, but to CW's low pH, high labile-carbon loading, and non-phenolic inhibitors. XRD and TGA confirmed Cd-bearing carbonate phases. Cd immobilization efficacy and crop safety were not monotonically coupled: TW gave the greatest dual benefit, PR was effective across a broader rate window, and CW required strict dose control.
