Biodegradation最新文献

Six chitinolytic strains of Janthinobacterium were isolated from the springs and reservoirs in Shulgan-Tash cave, which is not only one of largest caves in Southern Urals with preserved Paleolithic painting dating back to about 20,000 years, but also a final link in the karst hydrosystem of Shulgan River basin. This study aimed to characterize chitin degradation by the isolated bacteria for comprehension of their involvement in carbon cycle proceeding in the local groundwater ecosystem. The isolates varied in their colony morphology and pigmentation; five of the strains produced violacein-like pigments, while the sole isolate synthesized red pigment similar to prodigiosin. All the isolates were identified as Janthinobacterium sp. based on 16S rRNA gene sequence, where five strains were clustered with most homology to type species, J. lividum, and the single strain, IB-RH, was located separately from this group on phylogenetic trees. The studied bacteria manifested psychrotolerant properties with temperature optima of growth and chitin destruction at 22–26 °C. The isolates generally produced extracellular chitinase in range 0.14–0.18 U/mL; the maximal enzyme’s yield reached to 6–8 days. The violacein-producing strain IB-ST-GO exhibited most rapid dynamics of the chitinase secretion together with highest growth indices and degradation degree of various chitinous substrates. The noticeable chitinase production by this strain and other isolates along with their ability to colonize and assimilate diverse chitinous substrates of crustaceans’ origin as sole carbon source evidence their potential contribution in processes of chitin degradation in the karstic and non-karstic groundwaters.

In order to address the growing concerns regarding the environmental impact of plastics and the related environmental implications of food waste, this study was conducted with the objective of producing poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) by Stenotrophomonas geniculata bacteria isolated from a municipal landfill and utilizing food waste as a substrate. FTIR, ¹H-NMR, GC–MS and thermal analyses were used to confirm the production of PHBV. The produced biopolymer has thermoplastic elastomer properties similar to those of natural rubber. Temperature, concentration of nitrogen and carbon sources and pH were considered as the main factors for optimizing PHBV production. At the optimum conditions, i.e., temperature 32.3 °C, pH 9, nitrogen and glucose concentrations of 13.25 g/L and 27.71 g/L, respectively, maximum produced PHBV and yield of 2.835 g/L, and 0.746 g/g cell dry weight were obtained empirically. Notably, this study is the first to demonstrate the use of the S. geniculata strain Flmat 1 species for the production of PHBV using structurally unrelated simple carbon source. This study's strategy deals with the global burden of food waste and subsequently produces the biopolymer, which is a waste-to-wealth conversion.

In this study, we analyzed the prokaryotic community and methanogenic activities in sludge samples collected from a full-scale internal circulation (IC) reactor used to treat brewery wastewater. The reactor performance was monitored over 15 months, and specific methanogenic activities were periodically measured in fresh sludge samples using CO₂/H₂ or acetate as substrates. The maximum hydrogenotrophic activities were consistently higher than maximum acetoclastic activities, suggesting the relevance of hydrogenotrophic methanogens in the sludge. Over six months, the prokaryotic community present in four sludge samples was analyzed using amplicon libraries and metagenomics. V4-16S rRNA amplicon libraries revealed the presence of a diverse microbial community dominated by Firmicutes and Bacteroidetes among bacterial phyla, and Halobacterota and Euryarchaeota among archaea. Furthermore, the 16S libraries constructed with cDNA were consistent with the methanogenic activity assays. A genome-centric metagenomics approach was used to assemble 42 high-quality metagenome-assembled genomes (MAGs), among which Methanothrix and Methanobacterium were the dominant archaeal members, and Acidobacteriota, Synergistota, Krumholzibacteriota, and Nitrospirota phyla were among the bacteria. Potential acetogenic members were explored via the fths gene; 15 MAGs contained this marker gene. A combination of methanogenic activity tests, amplicon libraries, and MAG analysis was used to gain insights into the prokaryotic structure and functional potential of the microbial community driving methane production in the reactor.

This study aimed to optimize biogas and methane production from Up-flow anaerobic sludge blanket reactors for treating domestic wastewater using advanced machine learning models—namely, eXtreme Gradient Boosting (XGBoost) and its hybridized form, XGBoost, integrated with particle swarm optimization (XGBoost-PSO). The key operational variables included time, flow rate, chemical oxygen demand (COD), pH, volatile fatty acids, total suspended solids, hydraulic retention time, alkalinity, and the organic loading rate. Empirical data used to train and validate the predictive models were acquired from the sequential treatment of laboratory-prepared low-strength synthetic wastewater and actual municipal wastewater samples. Data was collected from two treatment phases: synthetic wastewater (COD: 335.45 ± 28.32 mg/L) was treated from days 0 to 270, followed by real domestic wastewater (COD: 225.28 ± 65.98 mg/L) from days 0 to 130. Gas production was continuously monitored throughout. The XGBoost-PSO model outperformed the standard XGBoost algorithm in both the training and testing phases. For biogas prediction during training, XGBoost-PSO achieved an RMSE of 0.0405, an MAE of 0.0225, and an R² of 0.9832, whereas for methane, the values were an RMSE of 0.0257, an MAE of 0.0175, and an R² of 0.9942. The testing results further confirmed the model’s robustness, with RMSE, MAE, and R² values of 0.1017, 0.0676, and 0.9404 for biogas and 0.0694, 0.0519, and 0.9717 for methane, respectively. These findings highlight the potential of integrating artificial intelligence-driven approaches to optimize bioenergy recovery in wastewater treatment systems.

Graphical abstract

n-Propylbenzene is an environmental pollutant belonging to a class of heavily used nonpolar alkylated aromatic solvents referred to as the C9 aromatics. Although n-propylbenzene is detected in different environmental matrices and displays toxicity, its bacterial biodegradation has been little explored. Consequently, few transformation products have been identified, and comprehensive biodegradation pathways were not constructed. Understanding n-propylbenzene biotransformation shall be useful to predict its fate and transport in the environment. Therefore, n-propylbenzene biotransformation by soil bacterium, Sphingobium barthaii KK22, was examined by liquid chromatography electrospray ionization tandem mass spectrometry (LC/ESI–MS/MS) through product ion scan collision induced dissociation (CID) analyses. Targeted CID of unknown biotransformation products resulted in the proposal of structures for at least 18 compounds and based upon these results, metabolites were organized into biotransformation pathways which revealed multiple routes to the TCA cycle. Decarboxylation of the n-propylbenzene alkyl side chain was proposed as a key part of the biodegradation process—so-called alkyl chain shortening. At the same time, the aromatic ring of n-propylbenzene was vulnerable to dioxygenation no matter the alkyl chain length or degree of alkyl chain oxidation resulting in numerous 3-, 2- and 1-carbon chain length compounds and their aromatic ring-opened counterparts. Quantitative analyses by LC and growth monitoring by absorbance confirmed that this bacterium eliminated 100 mg/L n-propylbenzene from culture media and that it utilized n-propylbenzene as a carbon source. In the natural environment, catabolically versatile soil sphingomonads such as S. barthaii may be contributors to the biodegradation of alkylated aromatic nonpolar pollutants such as n-propylbenzene.

In this study, two pretilachlor-degrading bacterial strains isolated from soil, Enterobacter sp. Pre1 and Pseudomonas sp. Pre2 completely utilized the compound as a sole carbon, energy and nitrogen source under aerobic conditions. The determination of degradation kinetics revealed that the rates of both isolates followed the Michaelis–Menten model, in which the maximum utilization rates of Enterobacter sp. Pre1 and Pseudomonas sp. Pre2 were 0.010 ± 0.0012 and 0.0060 ± 0.0007 mM/h, respectively. Moreover, Pseudomonas sp. Pre2 exhibited effective degradation of butachlor. Enterobacter sp. Pre1 showed better biofilm formation than the later one. Their immobilized biomass in polyurethane foam (PUF) reached 323.4 ± 35.6 mg/g PUF completely degrading pretilachlor at 0.15 mM within 12 h in a packed bed bioreactor. A metabolite, 2,6-diethylaniline, was produced during the degradation by both strains. Besides, 4-amino-3,5-diethyl phenol and aniline were the metabolites in the degradation by Enterobacter sp. Pre1 and Pseudomonas sp. Pre2, respectively. This study confirmed the efficiency and mechanisms in the degradation of pretilachlor by freely suspended and immobilized cells of the isolated bacteria.

Rapid industrialization and advancement of chemical fertilizers in agriculture get infused with water causing heavy pollution of inorganic pollutants has become a serious problem. This research focuses on the utilization of a thermophilic bacteria Brevibacillus borstelensis, SSAU-3 T in the bioremediation of hexavalent chromium (Cr (VI)). The strain has capability in > 99% removal of 40 ppm Cr (VI). Further optimization was studied by varying parameters (pH, Inoculum size, salinity, volume and temperature) based on Cr(VI) removal capabilities. Removal mechanism was determined by studying thermodynamic, kinetic, and isotherm under optimized parameters: pH 7, salinity 5 g/L, inoculum size 2%, medium volume 20 mL, temperature 55 °C which resulted that Redlich-Peterson isotherm model is a best fit for this study. Characterization of functional groups and bonds present on bacterial cell surface before and after treatment with chromium were optimized by Fourier Transform Infrared Spectroscopy and surface morphology changes were also observed by Scanning Electron Microscopy. A phytotoxicity study was conducted on wheat, which showed that bacterial secondary metabolites were not toxic. The study highlights an eco-friendly and cost-effective approach to mitigate Cr(VI) toxicity using thermophilic microbes from hot springs.

This study focused on the mycotransformation of a very prominent PAH, anthracene, and its acute toxicity reduction by Ascomycete fungi: Trichoderma lixii strain FLU1 (TlFLU1) and Talaromyces pinophilus strain FLU12 (TpFLU12), indigenously isolated from benzo[b] fluoranthene-enriched activated sludge. The results indicate that both the isolates TlFLU1 and TpFLU12 could tolerate anthracene exposure up to 1000 mg/L, with increased expression of ligninolytic enzymes: Laccase, Lignin peroxidase, and Manganese peroxidase. The mycotransformation of anthracene was observed to be growth-linked and mediated by the expression of the intracellular enzymes as the initial mechanism used by these strains followed by the ligninolytic enzymes with up to 56% and 38% anthracene degradation by TlFLU1 and TpFLU12, respectively, after 24 days with a concomitant change in pH from 5 to 4 (TlFLU1) and 6.2 (TpFLU12). The GC–MS and FTIR analysis of the samples indicate the appearance of metabolic intermediates: 9,10 anthracenedione and benzoic acid in TlFLU1 grown medium, while anthrone and 9,10 anthracenedione were detected in TpFLU12 grown medium. The mycotransformation of the compound followed a first-order kinetic model with an effective concentration (EC₅₀) of 262.3–266.1 mg/L, with a toxicity unit (TU) of 0.4% in Vibrio parahaemolyticus (6 h exposure) to each intermediate. Results show efficient mycotransformation of anthracene into a non-toxic state by TlFLU1 and TpFLU12.

The accumulation of fats, oils, and grease (FOG) in wastewater systems presents major environmental challenges, necessitating the development of effective bioremediation strategies. Biosurfactant-producing bacteria are promising for FOG degradation; however, their efficacy is highly pH-dependent, affecting microbial metabolism and biosurfactant stability. This study evaluates the impact of pH on FOG biodegradation by locally isolated biosurfactant-producing bacterial consortia to identify optimal pH conditions. Two highly efficient biosurfactant-producing bacterial isolates, identified via 16S rRNA sequencing as Pseudomonas aeruginosa and Bacillus velezensis, were cultured in Bushnell Haas (BH) medium to form a bacterial consortium. The consortium was then inoculated into fresh BH medium, adjusted to pH values from 4 to 9, and supplemented with 1% FOG (w/v). Samples were monitored at six-day intervals for 30 days under continuous shaking at 130 rpm. After 30 days of biodegradation, the solid FOGs in pH 6 disappeared while flocs were observed in both pH 4 and 5. Despite greater floc formation at pH 6, GC–MS analysis revealed that pH 4 achieved the highest degradation rate, displaying the fewest FOG peaks and the lowest area under peaks, indicating the most substantial FOG reduction. Notably, the consortium achieved the highest FOG removal at pH 4, an acidic condition under which most long-chain FOG components were completely degraded or transformed into shorter chains. This finding reveals an unexpected optimum pH 4 for FOG bioremediation by two efficient biosurfactant-producing bacteria combined into a synergistic consortium, highlighting a potential strategy to enhance grease waste treatment.