International Biodeterioration & Biodegradation最新文献

The anaerobic membrane biofilm reactor (An-MBfR) using dead-end hollow fiber membranes (HFMs) inevitably suffers the limited supply of gaseous electron donors to biofilms, as a result of the back-diffusion of inert gases. The microbial mechanisms, underlying the biofilm formation and decontamination performance of the An-MBfR disadvantaged by limited active gas supply, are still obscure in the literature. Herein, we investigated the evolution laws of biofilm ecology and function in a denitrifying H₂-based An-MBfR, from a multidimensional perspective. Results showed that despite the operating parameters of the reactor were set at the optimal values, the ununiform biofilms were developed on the HFMs, exhibiting a variation trend that with increasing distance from the near-gas end, the thickness and biomass of biofilms were decreased accompanied by their morphological change from the compacted to loosened. As hydrogenotrophic denitrifying bacteria (DNB) suffered limited H₂ supply to the biofilm, they could not produce abundant extracellular polymeric substances (EPS) and result in a high ratio of protein/polysaccharide (PN/PS) ratio in the EPS to facilitate the biofilm growth; their proliferation slowed down, especially in the outer layer of the biofilm at the far-gas end. The propagation of heterotrophic DNB was more active in the outer layer rather than inner layer of biofilms, ascribed to the abundant presence of PN and PS as well as increased NO₃⁻ availability. The variation trends in abundance of functional genes pertinent to the biofilm formation and NO₃⁻ reduction coincided well with the evolution laws of biofilm characteristics and DNB distribution. The findings provided mechanistic insights into the biofilm structure and microbial interaction in the denitrifying An-MBfR.

This study investigates the response of biofilm characteristics to variations in fluid depth and their influence on the corrosion behavior of carbon steel (C1020) under low-flow fluid conditions, utilizing Desulfovibrio vulgaris. The experiments were conducted in an anaerobic chamber at 30 °C, utilizing modified Baar's medium as the testing medium. The findings reveal that fluid depth significantly impacts biofilm-corrosion product composite formation, with deeper depths promoting thicker and more heterogeneous biofilm-corrosion product layer compared to shallower depths, where a thinner and more uniform biofilm-corrosion product layer is observed. Moreover, the characteristics of initially attached biofilms was verified as the primary factor affecting subsequent corrosion behavior during prolonged exposure. Corrosion analysis reveals that greater fluid depth leads to increased weight loss (91 ± 13.2 mg/cm²) and deeper pit depths (540 ± 69 μm), surpassing those observed in shallower test media (21 ± 2.3 mg/cm² and 105 ± 17 μm) after 28 days of exposure. The corrosion products within the biofilm were predominantly FeS and Fe₃(PO₄)₂·8H₂O. A direct relationship was observed between the thickness of this biofilm-corrosion product layer and the progression of pit depth, suggesting a strong correlation between carbon steel corrosion and biofilm development in limited fluid depths (e.g., 5–15 mm). Furthermore, a significant association between the deepest pits (average) and the number of sessile cells within the biofilm underscores the pivotal role of sessile cell numbers in carbon steel corrosion.

Nitrophenol pollutants, including para-nitrophenol (p-NP), are known for their harmful environmental impact due to their persistence, toxicity, and widespread distribution in water sources. While biodegradation generally offers a more effective removal of organic pollutants compared to chemical or physical methods, degrading persistent and toxic compounds like p-NP remains challenging. In this study, a microbial community derived from food processing wastewater was immobilized on coconut coir and adapted to p-NP before being employed for p-NP biodegradation. The spectroscopic analysis demonstrates the effective biodegradation performance of the adapted microbial community, achieving 99% degradation of 50 mg L⁻¹ p-NP in 38 min and 250 mg L⁻¹ p-NP in 4.65 h. The degradation ability of immobilized cells was determined across a broad range of stirring speeds, temperatures, pH levels, and p-NP solution volumes. Complete mineralization of p-NP was confirmed by chemical oxygen demand (COD) measurements of the treated solution and in-situ CO₂ generation. Notably, the p-NP degradation performance of the adapted immobilized microbial community remained stable for the first 40 days, with only a slight decrease observed after 47 days of cold preservation at 4 °C. An average p-NP degradation rate of 0.75 mg L⁻¹ min⁻¹ was maintained over 54 consecutive runs. Significant alterations in microbial diversity were identified through 16S metabarcoding analysis. The unadapted microbial community comprised a diverse range of genera, while the adapted community showed reduced diversity with an enrichment of specific genera known for p-NP degradation, such as unidentified members of the Micrococcaceae family, Paenarthrobacter spp., and Zoogloea spp.

Groundwater pollution is an important problem threatening the ecological environment and people's health, so it's very necessary to remedy the polluted groundwater. For the past few years, bioelectrochemical systems (BESs) have been widely used to remedy various polluted environments such as gas, water and solid. This is mainly attributed to following characteristics of BESs: (ⅰ) electrode can act as measureless electron acceptor/donor; (ⅱ) electrode surface can support the growth of microorganisms; (ⅲ) the electric field can stimulate naturally occurring microbial degradation activity; and (ⅳ) little or even no energy consumption. These properties enable BESs to degrade pollutants in an environmentally sustainable manner and improve the possibility of complete removal of pollutants. Therefore, this makes a lot of researchers choose to apply BESs to remediate polluted groundwater in situ. In order to fully understand BESs, this paper summarized from different aspects. Primarily, the remediation mechanism and main forms of BESs were described. Then, the application and research progress of BESs for the single and mixed pollutants removal in groundwater were reviewed. The principal variables affecting degradation performance were presented, including electrode potential, initial pollutant concentration, pH, carbon source and other process parameters and environmental conditions. Further, strategies to enhance the remediation performance of BESs were also discussed from the aspects of optimizing the system configuration, inoculating pre-enhanced microorganisms, adding redox medium and surfactant. Finally, the potential research direction of removing groundwater pollutants by BESs was proposed.

To develop new methods for transforming waste resources such as landfill leachate and weathered coal into clean energy, this research analyzed the co-fermentation effect and internal mechanism of methane production through gas chromatography, three-dimensional fluorescence, inducive coupling and metagenomics techniques. Our findings revealed that landfill leachate addition drives more than 70% increase in weathered coal biomethane production. Anaerobic fermentation collectively increased the tryptophan content in liquid-phase biodegradation, with the highest proportion reaching up to 72%. Paracoccus, Ralstonia, Aquamicrobium and other major microorganisms were in the range of 9–32%. Contamination of heavy metal diversity resistance genes has impacted microflora composition, with specialized heavy metal resistance genes such as NreB, CopD, NreB, and MerP altering the influence of heavy metals on anaerobic fermentation. The combined anaerobic fermentation of landfill leachate and weathered coal has expanded clean waste utilization and has broad application prospects.

Marine coastal zones face pollution from both terrestrial and marine petroleum sources. Chemical and biological surfactants are employed to enhance oil dispersal and bioavailability in seawater, yet comparisons of their effects on microbial communities and oil degradation in sediments have not been well documented. Here, we conducted microcosm experiments mimicking oil spill scenarios with coastal sediment from the East China Sea, amended with either a dispersant (Jiefeite or Slickgone NS) or the biosurfactant rhamnolipid. The addition of Jiefeite, Slickgone, and rhamnolipid significantly enhanced oil biodegradation in sediments, with similar effects among them. The enhanced biodegradation activities observed were correlated with increased abundances of phnAc and alkB genes, as well as elevated abundances of predicted functional genes for the degradation of chloroalkane, chloroalkene, benzoates, toluene, and aromatic hydrocarbon. All oil microcosms showed significant growth in Sulfurovum and Woeseia. Oil microcosms treated with Jiefeite or Slickgone specifically enriched potential oil-degraders like Syntrophotalea, Marinobacter, and Sphingomonadaceae. In contrast, rhamnolipid-treated microcosms stimulated a more diverse community of oil-degrading bacteria, exhibiting increased abundances of Pseudomonas, Lachnospirales, Aestuariicella, Vibrio, and Marinobacterium. Our findings underscore the differential impacts of chemical dispersants and rhamnolipid on oil-degrading bacterial communities and their enhanced impacts on oil biodegradation, highlighting their potential in remediation of oil pollution in coastal sediments.

This research explores how decay works and how different variables can affect this process in marine environments. The results are based on asterozoan echinoderms to cover one of the most complex multi-element skeletons in nature. Long-term experiments evaluated the effects of light, energy, salinity, sediment, oxygenation, temperature, and scavenger activity. The results showed that seven major agents can accelerate decay, including algal growth, water energy, microbial activity, microscavengers, macroscavengers, bubble production, and water acidification. Rapid burial of living organisms is the main shortcut to the fossilization of articulated specimens, but burial days to weeks after death can still lead to preservation if exceptional conditions delay the decay agents. Abrupt changes in salinity and temperature can restrict the distribution of scavengers and microorganisms, helping to preserve carcasses in the long term. Deeper or turbid seafloors can prevent small skeletons from destabilising due to the rapid growth of filamentous algae. Stagnant waters can also protect carcasses from waves and bottom currents, while water stratification can attenuate the attack of microscavengers. Although anoxia favours the preservation of soft parts, it is unable to prevent the anaerobic attack of microscavengers, which accelerates the destruction of small hard parts. Microbial reduction in anoxic regions can also drive the production of bubbles and the acidification of the water column, accelerating the destruction and dissolution of carbonate elements. These insights review important taphonomic concepts and provide a useful guide for interpreting the preservation potential of delicate organisms throughout the geological record.

Quinolinic acid (QA), a natural pyridine derivative produced through the kynurenine pathway in living organisms, is linked to various neurodegenerative diseases due to its neurotoxicity. Although some bacteria have been reported to degrade QA, the underlying molecular mechanisms remain incomplete. In this study, a unique qut cluster responsible for QA degradation is identified in Pigmentiphaga sp. YJ18. The strain YJ18 could degrade and utilize QA as the sole carbon source for growth. Strain YJ18 efficiently degrade 100 mg/L QA within 48 h at 30 °C, pH 7.0, and 1% NaCl. The gene-disruption results showed that qutE is involved in the initial step of QA degradation, while qutI mediate the conversion of 6-hydroxypicolinic acid (6HPA) to downstream metabolites. Furthermore, the degradation of QA is negatively regulated by the MarR family transcriptional regulator QutR, which shared 61.97% amino similarity with PicR in Alcaligenes faecalis. The qut gene cluster consists of three transcriptional units: qutABCDEF, qutGHIJKLMNO, and qutR. Electrophoretic mobility shift assay results demonstrated that QutR binds to the promoter regions of the qutA, qutG, and qutR, respectively, sharing a partial palindromic motif 5′-TCAG-N4-CTNN-3’. Bioinformatics analysis reveals that the unique qut cluster, co-evolving with Pigmentiphaga strains, integrating the qui and pic clusters which are responsible for degradation of QA to 6HPA and picolinic acid to fumaric acid, respectively. Overall, this study provides a newly isolated strain capable of degrading QA with a unique qut cluster and valuable molecular insights into the diversity of QA catabolic mechanisms in bacteria.

Phorate, an organophosphorus compound is known to have applications against pests. However, its hazardous nature is a matter of concern. Microbial biodegradation is a potent method that can eliminate pesticides from the environment by enzymatic reactions. As toxicity and binding specificity are inherently correlated to each other, this study was focussed on finding out binding sites for ensuing biodegradation. Brevibacterium frigoritolerans GD44 and Enterobacter cloacae subsp. cloacae ATCC 13047 were included in the study for genomic and structural analyses as alkaline phosphatase from Brevibacterium frigoritolerans GD44 and endonuclease/exonuclease/phosphatase from Enterobacter cloacae subsp. cloacae ATCC 13047 were found to degrade phorate. It was apparent from the present findings that alkaline phosphatase containing homologous bacterial species are AT-rich, while the phosphatase containing bacteria are GC-rich. Bacterial species having phosphatase enzyme contain more aromatic amino acids that stabilize the protein structure than alkaline phosphatase containing bacteria. Variation of relative synonymous codon usage (RSCU) value was found to be very little and natural selection pressure was preferred over mutational pressure in determining codon usage pattern. High level of codon adaptation index (CAI) found in both the bacterial species indicates higher level of codon usage bias and gene expression in them. Furthermore, docking results suggest that alkaline phosphatase has higher binding affinity to phorate than phosphatase that might be considered effective in bioremediation. The results obtained are considered to shed further light in the experimental biodegradation of organophosphorus pesticides by the bacteria.

An extracellular esterase (HP) with polybutylene succinate (PBS)-degrading ability was identified from Pseudomonas mendocina SA-1503. The HP also had the ability to degrade poly(3-hydroxybutyrate-co-4-hydroxybutyrate) and polycaprolactone. This HP had optimal activity at pH 9.0 and 40 °C and remained stable at pH 8.0–9.0 and temperatures of 30–40 °C. Mn²⁺ promoted the enzyme activity. HP could hydrolyze all p-NP fatty acid ester substrates containing even numbers of carbon atoms from C2 to C18 and had the highest catalytic activity for the p-NP C6 substrate. After 60 h of HP-catalyzed degradation, PBS films experienced a weight loss of more than 60%. Butanedioic acid, 1,4-butanediol, and a series of oligomers were detected in the degradation products of PBS by HP. Further structural analysis of HP revealed that it could be classified as a microbial esterase of α/β hydrolase superfamily and contained a conserved catalytic triad structure (Ser-148, Asp-198, and His-228) with a relatively exposed active site.