Aerobic Biodegradation Research Articles

A Kinetic Study on Chronic Response of Activated Sludge to Diclofenac by Respirometry

The present study investigated the chronic response of activated sludge to the emerging pollutant diclofenac as well as its aerobic biodegradation potential at different sludge retention times (SRTs). The impact of prolonged exposure to diclofenac on microbial process kinetics was explored with respirometric modelling. The long-term operation of lab-scale reactors revealed that continuous feeding of diclofenac at relevant concentrations observed in municipal wastewaters did not affect carbon removal efficiency independentl of SRT. However, in case of diclofenac removal, 34% efficiency could be achieved at a higher SRT of 20 days. Kinetic evaluation showed that the increment in diclofenac dosing resulted in no adverse effect on the microbial growth rate except that high concentrations of diclofenac exposure decreased the growth rate at SRT of 10 days. A significant increase in hydrolysis rate was determined in the diclofenac-acclimated biomass for both SRTs; even at high concentrations of diclofenac exposure, the hydrolysis rate remained unchanged. Long-term acclimation to diclofenac had a progressive impact on the hydrolysis kinetics, which could be attributed to an alteration in the microbial culture profile. Overall, the results suggest that the operation with diclofenac-acclimated biomass at higher SRTs could enrich a microbial culture capable of overcoming the adverse effect of the pollutant and improve the biodegradation potential as well.

Wheat Bran and Saccharomyces Cerevisiae Biomass’ Effect on Aerobic and Anaerobic Degradation Efficiency of Paper Composite

This study is a continuation of research on sustainable food packaging materials made from locally available feedstock and industrial by-products within the Baltic Sea region. Its main focus is the impact of wheat bran filler and Saccharomyces cerevisiae additive, which was used to develop a novel bio-coating for paper composite packaging, on the biodegradation efficiency of paper composites under aerobic and anaerobic conditions. In this study, we analyzed the effect of 15% and 40% concentrations of wheat bran filler and Saccharomyces cerevisiae biomass on the biodegradation efficiency of paper composites. This research was conducted under controlled environmental conditions, with aerobic biodegradation tested at 46 °C in a compost-based mesophilic–thermophilic environment and anaerobic biodegradation tested at 55 °C in an active inoculum thermophilic environment. The results show that the presence of wheat bran filler significantly improves biodegradation efficiency compared to microcrystalline cellulose reference material. Under aerobic conditions, the biodegradation efficiency for the 40% wheat bran and yeast sample was 6.34%, compared to only 0.71% for the cellulose reference material. In anaerobic conditions, the 15% wheat bran and yeast sample showed a biodegradation efficiency of 96.62%, compared to 82.32% for the cellulose reference material.

Hydrocarbon-degrading microbial populations in permanently cold deep-sea sediments in the NW Atlantic

Permanently cold deep-sea sediments (2500–3500 m water depth) with and without indications of thermogenic hydrocarbon seepage were exposed to naphtha to examine the presence and potential of cold-adapted aerobic hydrocarbon-degrading microbial populations. Monitoring these microcosms for volatile hydrocarbons by GC–MS revealed sediments without in situ hydrocarbons responded more rapidly to naphtha amendment than hydrocarbon seep sediments overall, but seep sediments removed aromatic hydrocarbons benzene, toluene, ethylbenzene and xylene (BTEX) more readily. Naphtha-driven aerobic respiration was more evident in surface sediment (0–20 cmbsf) than deeper anoxic layers (>130 cmbsf) that responded less rapidly. In all cases, enrichment of Gammaproteobacteria included lineages of Oleispira, Pseudomonas, and Alteromonas known to be associated with marine oil spills. On the other hand, taxa known to be prevalent in situ and diagnostic for thermogenic hydrocarbon seepage in deep sea sediment, did not respond to naphtha amendment. This suggests a limited role for these prevalent seep-associated populations in the context of aerobic hydrocarbon biodegradation.

Efficient and sustainable removal of linear alkylbenzene sulfonate in a membrane biofilm: Oxygen supply dosage impacts mineralization pathway

Linear alkylbenzene sulfonate (LAS) can be thoroughly mineralized within sufficient oxygen (O2), but which is energy intensive and may causes serious foaming problem. Although cometabolism can achieve efficient LAS removal within a wide range of O2 dosages, how O2 dosage systematically affects LAS metabolic pathway is still unclear. Here, membrane aerated biofilm reactor (MABR) enabled accurate O2 delivery and bulk dissolved oxygen (DO) control. MABR achieved efficient removal of LAS (>96.4 %), nitrate (>97.8 %) and total nitrogen (>96.2 %) at the three target DO conditions. At high DO condition (0.6 mg/L), LAS was efficiently removed by aerobic mineralization (predominant) coupled with aerobic denitrification biodegradation with the related functional enzymes. Pseudomonas, Flavobacterium, Hydrogenophaga, and Pseudoxanthomonas were dominant genus contributing to four possible LAS aerobic metabolic pathways. As O2 dosage reduced to only 29.7 % of the demand for LAS mineralization, O2 facilitated LAS activation, benzene-ring cleavage and a portion of respiration. NO3--N respiration-induced anaerobic denitrification also contributed to ring-opening and organics mineralization. Desulfomicrobium and Desulfonema related two possible anaerobic metabolic pathways also contributed to LAS removal. The findings provide a promising strategy for achieving low-cost high LAS-containing greywater treatment.

Biodegradation of linear alkylbenzene sulfonate contamination by pseudomonas aeruginosa isolates

Linear alkylbenzene sulphonate (LAS), a surfactant frequently incorporated into detergent formulations, typically ends up in wastewater treatment facilities after use. The present study aims to investigate the efficacy of bacteria isolated from Iraqi wastewater in removing LAS. This strain was identified as Pseudomonas aeruginosa by genetic analysis (16S rRNA). Three LAS concentrations (25, 50, and 100 mg/l) were employed in this investigation, along with three temperatures (30, 35, and 40 oC) and pH values (5, 7, 9). The LAS anionic surfactant demonstrated optimal biodegradation by Pseudomonas aeruginosa at a temperature of 30 °C and at pH levels of 7 and 9, with removal percentages of 93.76% and 90.4%, respectively, at a concentration of 25 mg/l of LAS. The study's findings demonstrated the possibility and importance of using aerobic biodegradation to remove LAS from actual effluents. This bacterium is useful for bioremediation because of its capacity to break down LAS.

Critical insights into data curation and label noise for accurate prediction of aerobic biodegradability of organic chemicals.

The focus of this work is to enhance state-of-the-art Machine Learning (ML) models that can predict the aerobic biodegradability of organic chemicals through a data-centric approach. To do that, an already existing dataset that was previously used to train ML models was analyzed for mismatching chemical identifiers and data leakage between test and training set and the detected errors were corrected. Chemicals with high variance between study results were removed and an XGBoost was trained on the dataset. Despite extensive data curation, only marginal improvement was achieved in the classification model's performance. This was attributed to three potential reasons: (1) a significant number of data labels were noisy, (2) the features could not sufficiently represent the chemicals, and/or (3) the model struggled to learn and generalize effectively. All three potential reasons were examined and point (1) seemed to be the most decisive one that prevented the model from generating more accurate results. Removing data points with possibly noisy labels by performing label noise filtering using two other predictive models increased the classification model's balanced accuracy from 80.9% to 94.2%. The new classifier is therefore better than any previously developed classification model for ready biodegradation. The examination of the key characteristics (molecular weight of the substances, proportion of halogens present and distribution of degradation labels) and the applicability domain indicate that no/not a large share of difficult-to-learn substances has been removed in the label noise filtering, meaning that the final model is still very robust.

Preparation of Block Copolymer-Stabilized Microspheres from Commercial Plastics and Their Use as Microplastic Proxies in Degradation Studies.

This study presents a novel one-pot procedure for preparing sub-10 μm poly(ethylene glycol) (MPEG)-stabilized glycol-modified poly(ethylene terephthalate), poly(ethylene terephthalate) (PET), poly(lactic acid) (PLA), polycarbonate, and polycaprolactone (PCL) particles from commercial plastics. The prepared particles can be dried and directly resuspended in water, making them easy to handle and relevant mimics of microplastics. In addition, the method was extended to the preparation of unstabilized PET particles and somewhat larger polyethylene (PE)-based particles. Selected stabilized microparticles were subjected to aerobic biodegradation studies and compared with nonstabilized PET particles. All of the particles exhibited some degradation. For PLA and PET particles, the degradation corresponded well to the amount of surface-stabilizing MPEG groups or known impurities, confirming that these polymers do not degrade under the applied conditions but that the stabilizing groups do. PCL particles degraded relatively rapidly, which is consistent with the literature data and their relatively small size. PE-based particles degraded more than expected if only degradation of the stabilizing groups was taken into account, indicating that the surface chemistry of these particles plays a role in bulk degradation.

Effect of Fe2+-activated persulfate combined with biodegradation in removing gasoline BTX from karst groundwater: A box-column experimental study.

In-situ chemical oxidation with persulfate (PS-ISCO) is a preferred approach for the remediation of fuel-contaminated groundwater. Persulfate (PS) can be activated by various methods to produce stronger sulfate radicals for more efficient ISCO. Despite karst aquifers being widespread, there are few reports on PS-ISCO combined with Fe2+-activated PS. To better understand the effects of Fe2+-activated PS for the remediation of gasoline-contaminated aquifers in karst areas, a box-column experiment was conducted under flow conditions, using karst groundwater and limestone particles to simulate an aquifer. Gasoline was used as the source of hydrocarbon contaminants. Dissolved oxygen and nitrate were added to enhance bioremediation (EBR) and ferrous sulfate was used to activate PS. The effect of Fe2+-activated PS combined with biodegradation was compared during the periods of EBR + ISCO and ISCO alone, using the mass flow method for data analysis. The results showed that the initial dissolution of benzene, toluene, and xylene (BTX) from gasoline injection was rapid and variable, with a decaying trend at an average pseudo-first-order degradation rate constant of 0.032 d-1. Enhanced aerobic biodegradation and denitrification played a significant role in limestone-filled environments, with dissolved oxygen and nitrate utilization ratios of 59 ~ 72% and 12-70%, respectively. The efficiency of EBR + ISCO was the best method for BTX removal, compared with EBR or ISCO alone. The pseudo-first-order degradation rate constants of BTX reached 0.022-0.039, 0.034-0.070, and 0.027-0.036 d-1, during the periods of EBR alone, EBR + ISCO, and ISCO alone, respectively. The EBR + ISCO had a higher BTX removal ratio range of 71.0 ~ 84.3% than the ISCO alone with 30.1 ~ 45.1%. The presence of Fe2+-activated PS could increase the degradation rate of BTX with a range of 0.060 ~ 0.070 d-1, otherwise, with a range of 0.034-0.052 d-1. However, Fe2+-activated PS also consumed about 3 times the mass of PS, caused a further decrease in pH with a range of 6.8-7.6, increased 3-4 times the Ca2+ and 1.6-1.8 times the HCO3- levels, and decreased the BTX removal ratio of ISCO + EBR, compared to the case without Fe2+ activation. In addition, the accumulation of ferric hydroxides within a short distance indicated that the range of PS activated by Fe2+ may be limited. Based on this study, it is suggested that the effect of Fe2+-activated PS should be evaluated in the remediation of non-carbonate rock aquifers.

Benzotriazole aerobic biodegradation by activated sludge and Bacillus sp. DH-12: Performance, community succession, and transformation products characterization

Understanding the biodegradation of benzotriazole compounds (BTs) is crucial for improving their removal from the environment. Experiments using activated sludge showed a 61.65 % removal rate for benzotriazole (BTA), primarily through biodegradation. Notably, microbial diversity changed significantly, especially within the class Bacilli, which increased from 0.17 % to 0.75 % over 21 days (p < 0.05). A novel Bacillus strain, DH-12, was identified, capable of degrading over 85 % of BTA and 5-methylbenzotriazole (MBT) within 24 hours. During the degradation of three BTs, seven possible intermediates were detected. Strain DH-12 appears to use methylation and carboxylation pathways for transformation and shows aerobic dechlorination ability. Additionally, this strain helps reduce the toxicity of BTs. This research enhances our understanding of BTs biodegradation by both microbial communities and a specific bacterial strain, offering valuable insights for environmental biotransformation strategies.

Biodegradation of sodium lauryl ether sulfate (SLES) contamination by Pseudomonas aeruginosa isolates

Sodium lauryl ether sulfate (SLES) is a surfactant commonly used in the formulation of detergents, which is typically disposed of in wastewater treatment plants. The current study describes the effectiveness of bacteria isolated from Iraqi wastewater to remove SLES. 16S rRNA genetic analysis revealed that this strain is Pseudomonas aeruginosa. Three temperatures (30, 35, and 40oC) and pH values (5,7, and 9) were chosen for this study, and three concentrations of SLES (25, 50, and 100 mg/L) were used. The SLES anionic surfactant showed that the best biodegradation by Pseudomonas aeruginosa was at a temperature of 30oC and both pH 7 and 9, while the removal percentages for them were 98.44% and 96.36%, respectively, at 25 mg/L of SLES. The outcomes of this study revealed the potential and significance of SLES removal in actual effluents by aerobic biodegradation. The ability of this bacterium to degrade SLES makes the bacterium an important tool for bioremediation.

Microplastics Biodegradation by Estuarine and Landfill Microbiomes

Plastic pollution poses a worldwide environmental challenge, affecting wildlife and human health. Assessing the biodegradation capabilities of natural microbiomes in environments contaminated with microplastics is crucial for mitigating the effects of plastic pollution. In this work, we evaluated the potential of landfill leachate (LL) and estuarine sediments (ES) to biodegrade polyethylene (PE), polyethylene terephthalate (PET), and polycaprolactone (PCL), under aerobic, anaerobic, thermophilic, and mesophilic conditions. PCL underwent extensive aerobic biodegradation with LL (99 ± 7%) and ES (78 ± 3%) within 50–60 days. Under anaerobic conditions, LL degraded 87 ± 19% of PCL in 60 days, whereas ES showed minimal biodegradation (3 ± 0.3%). PE and PET showed no notable degradation. Metataxonomics results (16S rRNA sequencing) revealed the presence of highly abundant thermophilic microorganisms assigned to Coprothermobacter sp. (6.8% and 28% relative abundance in anaerobic and aerobic incubations, respectively). Coprothermobacter spp. contain genes encoding two enzymes, an esterase and a thermostable monoacylglycerol lipase, that can potentially catalyze PCL hydrolysis. These results suggest that Coprothermobacter sp. may be pivotal in landfill leachate microbiomes for thermophilic PCL biodegradation across varying conditions. The anaerobic microbial community was dominated by hydrogenotrophic methanogens assigned to Methanothermobacter sp. (21%), pointing at possible syntrophic interactions with Coprothermobacter sp. (a H2-producer) during PCL biodegradation. In the aerobic experiments, fungi dominated the eukaryotic microbial community (e.g., Exophiala (41%), Penicillium (17%), and Mucor (18%)), suggesting that aerobic PCL biodegradation by LL involves collaboration between fungi and bacteria. Our findings bring insights on the microbial communities and microbial interactions mediating plastic biodegradation, offering valuable perspectives for plastic pollution mitigation.

Compound-Specific Carbon, Nitrogen, and Hydrogen Isotope Analysis to Characterize Aerobic Biodegradation of 2,3-Dichloroaniline by a Mixed Enrichment Culture.

Compound-specific isotope analysis (CSIA) is an established tool to track the in situ transformation of organic chemicals at contaminated sites. In this work, we evaluated the potential of multi-element CSIA to assess biodegradation of 2,3-dichloroaniline (2,3-DCA), which is a major industrial feedstock. Using controlled laboratory experiments, we determined, for the first time, negligible carbon (<0.5‰) and hydrogen (<10‰) isotope fractionation and a significant inverse nitrogen isotope fractionation (>10‰) during aerobic 2,3-DCA biodegradation by a mixed enrichment culture. The tentative identification of a glutamate conjugate of 2,3-DCA as a reaction intermediate indicates that the initial multistep enzymatic reaction may be rate-limiting. The formation of the glutamate adduct would increase the bond energy at the N atom, thus likely explaining the observed inverse N isotope fractionation. The corresponding nitrogen enrichment factor was +6.8 ± 0.6‰. This value was applied to investigate the in situ 2,3-DCA biodegradation at a contaminated site where the carbon and nitrogen isotope signatures from field samples suggested similar aerobic processes by native microorganisms. Under the assumption of the applicability of the Rayleigh model in a pilot wetland treating contaminated groundwater, the extent of biodegradation was estimated to be up to 80-90%. This study proposes multi-element CSIA as a novel application to study 2,3-DCA fate in groundwater and surface water and provides insights into biodegradation pathways.

Semi-rational design of nitroarene dioxygenase for catalytic ability toward 2,4-dichloronitrobenzene.

Rieske non-heme dioxygenase family enzymes play an important role in the aerobic biodegradation of nitroaromatic pollutants, but no active dioxygenases are available in nature for initial reactions in the degradation of many refractory pollutants like 2,4-dichloronitrobenzene (24DCNB). Here, we report the engineering of hotspots in 2,3-dichloronitrobenzene dioxygenase from Diaphorobacter sp. strain JS3051, achieved through molecular dynamic simulation analysis and site-directed mutagenesis, with the aim of enhancing its catalytic activity toward 24DCNB. The computationally predicted activity scores were largely consistent with the detected activities in wet experiments. Among them, the two most beneficial mutations (E204M and M248I) were obtained, and the combined mutant reached up to a 62-fold increase in activity toward 24DCNB, generating a single product, 3,5-dichlorocatechol, which is a naturally occurring compound. In silico analysis confirmed that residue 204 affected the substrate preference for meta-substituted nitroarenes, while residue 248 may influence substrate preference by interaction with residue 295. Overall, this study provides a framework for manipulating nitroarene dioxygenases using computational methods to address various nitroarene contamination problems.IMPORTANCEAs a result of human activities, various nitroaromatic pollutants continue to enter the biosphere with poor degradability, and dioxygenation is an important kickoff step to remove toxic nitro-groups and convert them into degradable products. The biodegradation of many nitroarenes has been reported over the decades; however, many others still lack corresponding enzymes to initiate their degradation. Although rieske non-heme dioxygenase family enzymes play extraordinarily important roles in the aerobic biodegradation of various nitroaromatic pollutants, prediction of their substrate specificity is difficult. This work greatly improved the catalytic activity of dioxygenase against 2,4-dichloronitrobenzene by computer-aided semi-rational design, paving a new way for the evolution strategy of nitroarene dioxygenase. This study highlights the potential for using enzyme structure-function information with computational pre-screening methods to rapidly tailor the catalytic functions of enzymes toward poorly biodegradable contaminants.

Aerobic biodegradation of poly(lactic acid) (PLA) in thermoplastic starch (TPS) blends in soil induced by gelatin

PLA is a biopolymer with great potential for use in agriculture, but its biodegradability in soil is slow. PLA degrading microorganisms exist in soil and their activity can be improved with the addition of proteins. The aim of this work was to study the effect of gelatin addition on the final biodegradation of TPS/PLA blends in soil. After 180 days, the final biodegradation percentages for TPS, GE and PLA were 96%, 79% and 0%, respectively. The extruded blends of TPS/PLA/GE, TPS/PLA and PLA/GE, presented ultimate biodegradability of 63%, 57% and 25% respectively. The biodegradation rate during the initial stages was reduced due to the interaction of the components, without affecting the final values. There was rapid biodegradation of the TPS and gelatin fractions in the materials, while PLA did not undergo any mineralization process in the soil. The inclusion of gelatin in the matrix and in the soil did not increase the biodegradability of the PLA fraction in the extruded, nor in the control blends because the microorganisms present in the inoculum did not assimilate the PLA.

Aerobic Biodegradation at a Seawater-Sediment Interface of a New Bioplastic 100% Based on Natural Polymers

Aerobic Biodegradation at a Seawater-Sediment Interface of a New Bioplastic 100% Based on Natural Polymers

Potential Role of Bioactive Compounds: In Vitro Evaluation of the Antioxidant and Antimicrobial Activity of Fermented Milk Thistle

The group of innovative ingredients in cosmetic preparations includes bio-ferments (Bs), which are characterized by high bioactivity and biocompatibility, and one of the plants rich in bioactive compounds that has a beneficial effect on the skin and the body is Silybum marianum. Bio-ferments obtained from this plant are becoming increasingly useful as active ingredients in cosmetics. In the present study, four different bio-ferments were obtained by fermentation of pomace (B-P), extract (B-E), oil (B-O), and seeds (B-S) of milk thistle. Their biodegradability (%B), total polyphenols content (Folin–Ciocalteu method), and antimicrobial, antioxidant (DPPH, ABTS, and FRAP methods), chelating (Fe2+ ions), and reduction (Cu2+ and Fe3+ ions) properties, as well as the acidity, were evaluated. The contact angle using the sessile drop method was assessed to investigate bio-ferments’ impact on skin wettability. Finally, the content of selected phenolic acids in the Bs was evaluated using the HPLC method, while the lactic acid (LA) content was assessed using the GC-MS method. All bio-ferments were characterized by high polyphenols content (13.56 ± 0.10–15.28 ± 0.12 mmol GA/L B), chelating (0.08 ± 0.01–0.17 ± 0.01 mmol Fe2+/L B) and antioxidant activity (DPPH method, 2.41 ± 0.01–3.53 ± 0.01 mmol Tx/L B), and reducing Cu2+ and Fe3+ ions. Gallic acid, protocatechuic acid, caffeic acid, neochlorogenic acid, coumaric acid, and LA were identified in Bs. The most increased antibacterial activity for B-P was observed for a strain of Staphylococcus aureus (MIC = 250 μL/mL) and Pseudomonas aeruginosa (MIC = 250 μL/mL). Simultaneously, B-S demonstrated the highest inhibitory effects against Escherichia coli (MIC = 125 μL/mL), emphasizing the varied antimicrobial profiles of these bio-ferments against different bacterial strains. Research on aerobic biodegradation demonstrated a high level of degradation (%B = 60 ± 1–65 ± 3), and all Bs were categorized as readily degradable according to the OECD classification.

Production of PLA/cellulose derived from pineapple leaves as bio-degradable mulch film

Mulch films were fabricated from polylactic acid (PLA) with cellulose nanocrystals (PNC) extracted from pineapple leaves. The PNC was modified by incorporating 4 wt% triethoxyvinylsilane (TEVS), designated as 4PNC, to enhance its interaction with PLA. The films incorporated varying concentrations of PNC (1, 2, 4, and 8 wt%). The results indicated that higher PNC concentrations increased the water vapor permeability (WVP) and biodegradability of the composite films, while reducing light transmission. Films containing 4PNC, particularly at 4 wt% (PLA/4PNC-4), exhibited an 11.18 % increase in elongation at break compared to neat PLA films. Moreover, these films showed reduced light transmission, correlating with decreased weed growth, reduced WVP, and enhanced barrier properties, indicative of improved soil moisture retention. Additionally, PLA films with 4PNC demonstrated greater thermal degradation stability than those with unmodified PNC, suggesting enhanced heat resistance. However, there was no significant difference in aerobic biodegradation between the PLA films with PNC and those with 4PNC. This study confirms that TEVS-modified cellulose significantly enhances the properties of bio-composite films, making them more suitable for mulch film applications.

Japanese washi-paper-based green composites: Fabrication, mechanical characterization, and evaluation of biodegradability

In this study, sheets of Japanese washi-paper were layered and hot pressed with films of poly(butylene succinate) (PBS) in order to produce a fiber-reinforced composite material that can be biodegraded. Using traditional Japanese washi-paper, a thin yet remarkably strong green composite with excellent biodegradability was produced, proving the potential of washi-paper as an attractive reinforcer in green composites. The composite was biodegraded in compost, and the ultimate aerobic biodegradability as well as weight loss and loss of mechanical properties during biodegradation was evaluated. Specimens fabricated from three layers of washi-paper and two layers of PBS film had remarkable mechanical properties, including an ultimate tensile strength of 59.85 MPa. Scanning electron microscopy was used to study the cross-sectional structure of the material, which showed that the hollow washi-paper provides a structure for the polymer to settle into and surround the cellulose fibers. The large contact area between the cellulose fibers and the PBS caused a large internal friction which prevented failure by fiber pull-out, dramatically increasing the strength compared to neat washi-paper and neat PBS. Concerning biodegradability, the material reached 82 % biodegradation after 35 days. During biodegradation, the composite lost its mechanical properties fast, and was extremely fragile after 2 weeks inside the compost. After 6 weeks, the biodegradation had progressed so far that it was difficult to distinguish the material inside the compost. Due to its fast biodegradation and good mechanical strength, the washi-based composite material is potentially used in packaging, furniture, and agricultural applications such as mulch film.

Sulfonamide Per- and Polyfluoroalkyl Substances Can Impact Microorganisms Used in Aromatic Hydrocarbon and Trichloroethene Bioremediation.

Per- and polyfluoroalkyl substances (PFASs) from aqueous film forming foams (AFFFs) can hinder bioremediation of co-contaminants such as trichloroethene (TCE) and benzene, toluene, ethylbenzene, and xylene (BTEX). Anaerobic dechlorination can require bioaugmentation of Dehalococcoides, and for BTEX, oxygen is often sparged to stimulate in situ aerobic biodegradation. We tested PFAS inhibition to TCE and BTEX bioremediation by exposing an anaerobic TCE-dechlorinating coculture, an aerobic BTEX-degrading enrichment culture, and an anaerobic toluene-degrading enrichment culture to n-dimethyl perfluorohexane sulfonamido amine (AmPr-FHxSA), perfluorohexane sulfonamide (FHxSA), perfluorohexanesulfonic acid (PFHxS), or nonfluorinated surfactant sodium dodecyl sulfate (SDS). The anaerobic TCE-dechlorinating coculture was resistant to individual PFAS exposures but was inhibited by >1000× diluted AFFF. FHxSA and AmPr-FHxSA inhibited the aerobic BTEX-degrading enrichment. The anaerobic toluene-degrading enrichment was not inhibited by AFFF or individual PFASs. Increases in amino acids in the anaerobic TCE-dechlorinating coculture compared to the control indicated stress response, whereas the BTEX culture exhibited lower concentrations of all amino acids upon exposure to most surfactants (both fluorinated and nonfluorinated) compared to the control. These data suggest the main mechanisms of microbial toxicity are related to interactions with cell membrane synthesis as well as protein stress signaling.

Process and quality evaluation of different improved composts made with a smart laboratory pilot plant

This study monitored the process and investigated the quality of compost obtained from different biomasses. Five blends of agri-food waste were composted by a laboratory pilot plant named COMPOSTER, that is designed to optimize biodegradation, and produce compost efficiently. The COMPOSTER consists of two 35-liter nearly adiabatic, aerated bioreactors that simulate an industrial process involving the typical sequence of mesophilic-thermophilic-mesophilic phases. It continuously monitors and records temperature, internal pressure, and biomass weight, while controlling and quantifying oxygen consumption and carbon dioxide emissions resulting from aerobic biodegradation. All composts were characterized for their main chemical, physical, and molecular features, as well as their suppressiveness against Fusarium oxysporum f.sp. lycopersici (FOL), tested on tomato seedlings. Optimized biodegradation yielded 50–60 % mature compost with a cumulative oxygen consumption ranging from 282 to 456 gO2 per kg of dry matter, with peaks of 2.55 gO2 per kg of volatile solids per hour, and carbon dioxide emissions of 22–36 % of the initial carbon content, with peaks of 5.89 g CO2 per kg of volatile solids per hour. Blends containing more ligno-cellulosic ingredients showed higher yields and lower CO2 emissions. Most of the nitrogen present initially was retained in the final compost; indeed, all mixtures exhibited an apparent nitrogen concentration increase due to carbon loss. Composting determined deep modifications in the molecular structure of the organic matter. 13C CPMAS-NMR and off-line thermochemolysis GC-MS analyses highlighted decomposition degree of polysaccharides and peptidic moieties, selective preservation of aliphatic and aromatic recalcitrant compounds, and optimal ongoing humification. All composts were non-phytotoxic, except for that including pepper crop residues, and all resulted rich in macro- and micro-elements for plant nutrition and proved to be active in controlling FOL disease. Compost comprising 81.2 % tomato crop waste exhibited the best growth performance and pathogen control on tomato. Mature, non-phytotoxic, nutrient-rich, and suppressive composts represent promising by-products that can be successfully recycled in agriculture, including high-value applications, leading to lower use of fertilizers and pesticides.