International Biodeterioration & Biodegradation最新文献

Nitrogen-containing organic compounds, such as amino acids in soybean-processing wastewater, can be used as electron donors to drive denitrification, but their biodegradation releases ammonium nitrogen that must be nitrified and denitrified to maintain total-nitrogen removal. We evaluated glutamate, isoleucine, and methionine as example amino acids to explore the fate of nitrogen when they are used as electron donor to drive denitrification during two stages of alternating denitrification and nitrification. The experimental results documented that each amino acid enabled complete removal of exogenous NO₃⁻ in the first stage of denitrification and complete NO₃⁻ removal in the second stage. After two alternations of denitrification and nitrification, the TN concentration in effluent was less than 5 mgN/L for all amino acids, and COD in the effluent was less than 25 mg/L. Based on stoichiometry and the ratio of chemical oxygen demand (COD) to organic N in each amino acid, 57%–66% of the COD from the amino acids had to be oxidized to reduce the endogenous NO₃⁻–N in the first stage. N from the amino acids was nitrified and denitrified in the subsequent nitrification and denitrification stages, and the percentages of COD used for denitrification from both stages were 72%–85%. The residual NH₄⁺-N concentrations were slightly higher with methionine, possibly due to inhibition from sulfide released from methionine.

The nitrification process plays an important role in the nitrogen cycle, in which the ammonia-oxidation process mediated by microorganisms is the rate-limiting step. Environmental factors can affect the distribution and activity of ammonia-oxidizing microorganisms (AOM), including ammonia-oxidizing bacteria (AOB), ammonia-oxidizing archaea (AOA), and complete ammonia oxidizer (comammox Nitrospira). At present, most studies have used amoA as a marker gene for the ammonia oxidation process to analyze the differences among AOM community composition and abundance in the environment. In this study, metagenomic sequencing was used to study the differences in community composition and functional gene distribution of nitrifying microorganisms in the sediments of Lake Taihu with different eutrophication levels. It was found that comammox Nitrospira and typical nitrite oxidizer NOB Nitrospira, which belong to Nitrospirota, had higher relative abundance at most sites compared to AOB and AOA. Furthermore, the network analysis of genes related to nitrogen cycle showed that the main survival mode of nitrogen metabolizing microorganisms was mutualism. Besides, the microbial genomes in the sediments of Lake Taihu were reconstructed by metagenomic binning, which showed that among the 167 bins obtained, 2 bins (bin 9 and bin 32) were annotated as comammox Nitrospira, and had high abundance in the macrophytes-dominated lakes (such as South Lake Taihu and West Coast). In addition, bin 9, which belongs to comammox Nitrospira, annotates amoA genes associated with ammonia oxidation, and other genes associated with urea decomposition and transport, suggesting functional diversity. Overall, these findings suggest that AOM have different distribution characteristics, among which comammox Nitrospira has high diversity and may be potentially dominant in macrophytes-dominated lakes.

Despite extensive research on the geographical patterns of microbial communities, our comprehension of the mechanisms underlying their spatial distribution is still limited. Natural ecosystems provide opportunities to investigate the structure, connectivity, and assembly processes of prokaryotic communities. Saline lakes, mangroves, ocean margins, cold seeps, and open oceans as five distinct natural ecosystems exhibit varied levels of salinity and nutrient condition (carbon sources, electron donors, and electron acceptors). Based on the analysis of 197 sets of published 16S rRNA gene amplicon sequencing data on sediment samples of the five habitats, differences in salinity and nutrient conditions were identified to play a critical role in governing the composition, connectivity, and assembly process of prokaryotic communities. Specifically, unique prokaryotic community patterns were observed in these habitats, e.g., mangrove sediment communities were shown to have the highest alpha diversity and the lowest community-level ribosomal RNA gene operon (rrn) copy numbers, compared to the open ocean sediment communities. Positive correlation predominated connections (>80% of total connections) of the prokaryotic microbial networks in the five habitats. Communities within nutrient-rich saline lake and cold seep sediments exhibit the strongest and closest connections. Using the dissimilarity-overlap curve and null model, differences in composition, connectivity, and assembly process were found to be predominantly governed by deterministic forces. These findings enhance our understanding of microbial ecology in typical saline environments and enable us to investigate intricate ecosystems.

The accumulation of butyrate is a recurrent phenomenon in anaerobic digesters utilizing animal manure as the primary feedstock. Despite its prevalence, the factors governing the anaerobic degradation of butyrate remain inadequately explored. In this study, a series of experiments were carried out under different total ammonia concentrations (TAN, 0.18–20 g N/L) and pH conditions (7.0–8.0) to investigate the inhibition of butyrate anaerobic degradation by different ammonia species (NH₄⁺ and NH₃) and to assess the recoverability following severe ammonia inhibition. The findings indicate that at pH 7.5, butyrate degradation experienced remarkable inhibition when TAN exceeded 8.0 g N/L, while no discernible impact was observed at pH 7.0–8.0 and 4.0 g TAN/L. Additionally, the lag phase for butyrate degradation extended with increasing TAN concentration. Notably, the activity of butyrate-degrading bacteria exhibited full recovery from severe ammonia inhibition (TAN 20 g N/L or NH₃ 779.2 mg N/L), provided prolonged adaption time was allowed. The analysis using a modified Monod inhibition model highlighted that NH₄⁺ contributed more to inhibition than NH₃ at TAN concentrations of 2.0–20.0 g N/L. Therefore, simply reducing pH levels would not adequately counteract ammonia inhibition. Implementing an extended hydraulic retention time emerges as an effective measure to reduce butyrate accumulation in anaerobic digestion systems, particularly the feedstock being nitrogen-rich materials (e.g., animal manure).

Acetaminophen's inherent solubility and hydrophilic nature facilitate its accumulation in aquatic ecosystems. Herein, Scenedesmus dimorphus IITISM-DIX1 demonstrates efficient acetaminophen removal, concurrently serving as a substrate for lipid biosynthesis. Employing Box-Behnken design, optimization of parameters like pH, light duration and concentration of acetaminophen influencing its elimination is executed. Characterization of pre- and post-algal biomass involves FE-SEM, FTIR, and BET analysis. Kinetic and adsorption analyses reveal pseudo-first-order kinetics (R² = 0.99) and adherence to the Freundlich isotherm (R² = 0.94). FTIR spectroscopy demonstrates subtle shifts in IR bands post-sorption, indicative of biomass involvement in adsorption processes. Biodegradation and biosorption serve as the main removal pathways, facilitated by exopolysaccharides, generating by-products such as 4-aminophenol, hydroquinone, and formic acid. The Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC) values obtained for the Freundlich isotherm validate it as the optimal model, indicating heterogeneous multilayered sorption with efficiency ranging from 44% to 100%. Additionally, exposure to acetaminophen-contaminated media leads to biochemical alterations in Scenedesmus dimorphus IITISM-DIX1. The findings of this study unveil the first elucidated pathway for acetaminophen degradation by any Scenedesmus species, delivering essential knowledge about microalgae-mediated acetaminophen degradation and lipid enrichment mechanisms.

It is necessary to develop appropriate approaches to eliminate para-nitrophenol (PNP) in our environment, because the pollutant is highly toxic and also able to persist in the environment. Previously, Pseudomonas sp. strain WBC-3 isolated from polluted soil was found to be able to use PNP as the sole carbon and nitrogen source, but not very efficiently. In this study, WBC-3 was shown to belong to Pseudomonas putida through de novo genome sequencing. To enhance its efficiency of PNP utilization, a mutant strain (PM1-33) with a significantly increased PNP degradation rate was obtained. Although no increase in the expression levels of known PNP catabolizing genes/proteins were observed between WBC-3 and PM1-33, the expression level of protein 1619 significantly increased in PM1-33. Deleting GM1619 in WBC-3 and PM1-33 caused decreased PNP degradation rates in both strains and eliminated the difference in PNP degradation between the two strains. Functional prediction using AlphaFold2 showed that protein1619 might bind to p-benzoquinone (BQ). Consequently, protein 1619 was biochemically characterized, confirming its ability to convert BQ into hydroquinone (HQ). Thus, a new protein involved in PNP degradation was identified, thereby adding new knowledge to bacterial PNP degradation pathways.

Using heat treatment for wood protection has been driven to maturity, but the role of heat-treated wood extracts in decay resistance has lacked attention. To assess the potential of heat-treated wood extract for wood preservation, the antifungal activity of the extract against wood decay fungi and the effects of the extract on fungal wood degrading enzyme activity and cell membrane integrity were tested. Small shavings generated during the processing of larch (Larix gmelinii (Rupr.) Kuzen) were heat-treated and extracted. The antifungal activity of extract against wood decay fungi and decay resistance of extract impregnated wood were tested to assess their potential. The effect of extracts on the enzyme activity of the white-rot fungus, Trametes versicolor (L.) Lloyd and the brown-rot fungus, Gloeophyllum trabeum (Pers.: Fr.) Murr. for wood degradation was assessed by detecting the activity of cellulose, hemicellulose, and ligninase of fungi incubated with extract. The effect of extracts on the integrity of cell membranes of fungi was assessed by staining with propidium iodide (PI) and the leakage detection of nucleic acid and protein in fungi after exposure to extract. The toxicity to freshwater luminescent bacteria (Vibrio qinghaiensis sp. -Q67) and mouse macrophages (RAW264.7) of the extract impregnated wood leachate was tested and compared with the leachate of the raw wood. The results denoted that the decay resistance of poplar (Populus tomentosa Carr.) wood could be improved by heat-treated larch wood extract, and the effect of the extract impregnated wood leachate on Q67 and RAW264.7 was the same as that of raw wood leachate. The extract inhibited ligninase activity (only for T. versicolor), cellulase activity, and respiratory metabolism of tested fungi, and impaired the membrane integrity. The study identified a potential wood preservative.

In this study, we validated various methods of pre-treatment of poly(ethylene terephthalate) (PET) by the engineered yeast Yarrowia lipolytica. This research compares both the effect of the type of plastic used, the processing method and enzymes with different mechanisms of action (PETase and cutinase). The investigation demonstrated that the degradation efficiency varies depending on the type of plastic used, the processing methods and the applied enzyme. Moreover, it indicated that during prolonged yeast culture under the applied conditions, enzyme activity is not impaired. Among all the methods tested, the artificial aging process had the greatest impact on the degradation level by PETase, where the amount of TPA released from commercial PET film was the highest, and yielded over 2 gL^-1. The maximum yield of TPA (0.59 gL^-1), for the Y. lipolytica strain overexpressing cutinase, was observed during the process with recycled PET bottles shredded into 1 mm fragments. The maximum recorded weight loss of plastic film is over 70% for commercial PET film subjected to artificial ageing process.

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.

Thermoplastic polyvinyl alcohol (TPVA) is a biodegradable polymeric plastic and is a promising alternative to traditional non-biodegradable plastics in a range of applications. However, the knowledge of anaerobic TPVA biodegradation is still limited. In this study, we evaluated the anaerobic biodegradation of two types of TPVA films manufactured using extrusion film casting and biaxial orientation methods. The results indicated that TPVA films prepared by extrusion casting were more rapidly degraded under anaerobic conditions, especially in cultures enriched from landfills than oil production water. 16S rRNA sequencing and functional prediction were performed by software PICRUSt. The results showed that members in Synergistales and Bacillales were likely responsible for secreting extracellular enzymes to depolymerize TPVA during the initial stage of the degradation process. Moreover, methanogens, such as Methanothermobacter, Methanoculleus, and Methanosarcina utilized the H₂, CO_2, and acetate produced from bacterial partners when degrading TPVA to generate methane. This work provides a comparative analysis and a basis for the process of anaerobic biodegradability of TPVA produced by different manufacturing processes. It is of significant importance for the future promotion of TPVA applications and the mitigation of environmental pollution.