Biodegradation最新文献

In order to explore the operation performance, kinetic characteristics and bacterial community of the short-cut nitrification and denitrification (SND) system, the SND system with pre-cultured short cut nitrification and denitrification sludge was established and operated under different ferrous ion (Fe (II)) conditions. Experimental results showed that the average NH₄⁺–N removal efficiency (ARE) of SND system was 97.3% on Day 5 and maintained a high level of 94.9% ± 1.3% for a long operation period. When the influent Fe(II) concentration increased from 2.3 to 7.3 mg L⁻¹, the sedimentation performance, sludge concentration and organic matter removal performance were improved. However, higher Fe(II) of 12.3 mg L⁻¹ decreased the removal of nitrogen and COD_Cr with the relative abundance (RA) of Proteobacteria and Bacteroidetes decreased to 30.28% and 19.41%, respectively. Proteobacteria, Bacteroidetes and Firmicutes were the dominant phyla in SND system. Higher Fe(II) level of 12.3 mg L⁻¹ increase the RA of denitrifying genus Trichococcus (33.93%), and the denitrifying genus Thauera and Tolumonas dominant at Fe(II) level of no more than 7.3 mg L⁻¹.

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Acetaldehyde (AL), a primary carcinogen, not only pollutes the environment, but also endangers human health after drinking alcohol. Here a promising bacterial strain was successfully isolated from a white wine cellar pool in the province of Shandong, China, and identified as Bacillus velezensis-YW01 with 16 S rDNA sequence. Using AL as sole carbon source, initial AL of 1 g/L could be completely biodegraded by YW01 within 84 h and the cell-free extracts of YW01 has also been detected to biodegrade the AL, which indicate that YW01 is a high-potential strain for the biodegradation of AL. The optimal culture conditions and the biodegradation of AL of YW01 are at pH 7.0 and 38 °C, respectively. To further analyze the biodegradation mechanism of AL, the whole genome of YW01 was sequenced. Genes ORF1040, ORF1814 and ORF0127 were revealed in KEGG, which encode for acetaldehyde dehydrogenase. Furthermore, ORF0881 and ORF052 encode for ethanol dehydrogenase. This work provides valuable information for exploring metabolic pathway of converting ethanol to AL and subsequently converting AL to carboxylic acid compounds, which opened up potential pathways for the development of microbial catalyst against AL.

Textile industries release major fraction of dyestuffs in effluents leading to a major environmental concern. These effluents often contain more than one dyestuff, which complicates dye degradation. In this study ten reactive dyes (Reactive Yellow 145, Reactive Yellow 160, Reactive Orange 16, Reactive Orange 107, Reactive Red 195, Reactive Blue 21, Reactive Blue 198, Reactive Blue 221, Reactive Blue 250, and Reactive Black 5) that are used in textile industries were subjected to biodegradation by a bacterial consortium VITPBC6, formulated in our previous study. Consortium VITPBC6 caused single dye degradation of all the mentioned dyes except for Reactive Yellow 160. Further, VITPBC6 efficiently degraded a five-dye mixture (Reactive Red 195, Reactive Orange 16, Reactive Black 5, Reactive Blue 221, and Reactive Blue 250). Kinetic studies revealed that the five-dye mixture was decolorized by VITPBC6 following zero order reaction kinetic; V_max and K_m values of the enzyme catalyzed five-dye decolorization were 128.88 mg L^-1 day^-1 and 1003.226 mg L^-1 respectively. VITPBC6 degraded the dye mixture into delta-3,4,5,6-Tetrachlorocyclohexene, sulfuric acid, 1,2-dichloroethane, and hydroxyphenoxyethylaminohydroxypropanol. Phytotoxicity, cytogenotoxicity, microtoxicity, and biotoxicity assays conducted with the biodegraded metabolites revealed that VITPBC6 lowered the toxicity of five-dye mixture significantly after biodegradation.

Industrial development and the associated generation of waste requires attention for their management, treatment, and reduction without further degrading the quality of life. Microbes and plant-based bioremediation approaches are some of the sustainable strategies for the biodegradation of harmful pollutants instead of chemical-based treatment. Bioaugmentation is one such approach where microbial strains with the ability to degrade the targeted pollutant are introduced in a polluted environment. Harnessing of microbes from various locations, especially from the site of contamination (indigenous microbes), followed by optimization of the strains, inoculum size, media, and genetic engineering of the microbes along with a combination of strategies such as bio stimulation, phytoremediation is being applied to increase the efficiency of bioaugmentation. Further, bioaugmentation is influenced by various factors such as temperature, the composition of the pollutant, and microbial inoculum which needs to be considered for maximum efficiency of the treatment process. It has numerous advantages such as low cost, sustainability, and easy handling of the contaminants however, the major limitation of bioaugmentation is to increase the survival rate of the microbes involved in remediation for a longer duration in such a highly toxic environment. The review discusses these various aspects of bioaugmentation in brief for its large-scale implementation to address the global issue of pollution and environment management.

Biodegradation rates and mechanical properties of poly(3-hydroxybutyrate) (PHB) composites with green algae and cyanobacteria were investigated for the first time. To the authors knowledge, the addition of microbial biomass led to the biggest observed effect on biodegradation so far. The composites with microbial biomass showed an acceleration of the biodegradation rate and a higher cumulative biodegradation within 132 days compared to PHB or the biomass alone. In order to determine the causes for the faster biodegradation, the molecular weight, the crystallinity, the water uptake, the microbial biomass composition and scanning electron microscope images were assessed. The molecular weight of the PHB in the composites was lower than that of pure PHB while the crystallinity and microbial biomass composition were the same for all samples. A direct correlation of water uptake and crystallinity with biodegradation rate could not be observed. While the degradation of molecular weight of PHB during sample preparation contributed to the improvement of biodegradation, the main reason was attributed to biostimulation by the added biomass. The resulting enhancement of the biodegradation rate appears to be unique in the field of polymer biodegradation. The tensile strength was lowered, elongation at break remained constant and Young's modulus was increased compared to pure PHB.

PHB depolymerase enzymes are able to breakdown the PHB polymers and thereby get significant economic value in the bioplastics industry and for bioremediation as well. This study shows the purification of novel extracellular PHB depolymerase enzyme from Aeromonas caviae Kuk1-(34) using dialysis followed by gel filtration and HPLC. The purification fold and yield after HPLC were 45.92 and 27.04%, respectively. HPLC data showed a single peak with a retention time of 1.937 min. GC-MS analysis reveals the presence of three compounds, of which 1-Dodecanol was found to be most significant with 54.48% area and 8.623-min retention time (RT). The molecular weight of the purified enzyme was obtained as 35 kDa with K_m and apparent V_max values of 0.769 mg/mL and 1.89 U/mL, respectively. The enzyme was moderately active at an optimum temperature of 35 °C and at pH 8.0. The stability was detected at pH 7.0-9.0 and 35-45 °C. Complete activity loss was observed with EDTA, SDS, Tween-20 at 5 mM and with 0.1% Triton X 100. A biodegradation study of commercially available biodegradable polymer films was carried out in a liquid medium and in soil separately with pure microbial culture and with purified enzyme for 7, 14, 28, and 49 consecutive days. In a liquid medium, with a pure strain of Aeromonas caviae Kuk1-(34), the maximum degradation (89%) was achieved on the PHB film, while no changes were observed with other polymer films. With purified enzyme in the soil, 71% degradation of the PHB film was noticed, and it was only 18% in the liquid medium. All such weight analysis were confirmed by SEM images where several holes, pits, grooves, crest, and surface roughness are clearly observed. Our results demonstrated the potential utility of Aeromonas caviae Kuk1-(34) as a source of extracellular PHB depolymerase capable of degrading PHB under a wide range of natural/ lab conditions.

The copper industry utilizes significant amounts of sulfuric acid in its processes, generating sulfate as waste. While sulfate-reducing bacteria can remove sulfate, it produces hydrogen sulfide (H₂S) as a byproduct. This study examined the capability of a consortium consisting of Sulfobacillus thermosulfidooxidans and Sulfobacillus acidophilus to partially oxidize H₂S to S° at a temperature of 45 °C. A fixed-bed bioreactor, with glass rings as support material and sodium thiosulfate as a model electron donor, was inoculated with the consortium. Formation of biofilms was crucial to maintain the bioreactor's steady state, despite high flow rates. Afterward, the electron donor was changed to H₂S. When the bioreactor was operated continuously and with high aeration, H₂S was fully oxidized to SO₄^2-. However, under conditions of low aeration and at a concentration of 0.26 g/L of H₂S, the consortium was able to oxidize H₂S to S° with a 13% yield. S° was discovered attached to the glass rings and jarosite. The results indicate that the consortium could oxidize H₂S to S° with a 13% yield under low aeration and at a concentration of 0.26 g/L of H₂S. The findings highlight the capability of a Sulfobacillus consortium to convert H₂S into S°, providing a potential solution for addressing environmental and safety issues associated with sulfate waste generated by the mining industry.

Tetracyclines are antibiotics considered emerging pollutants and currently, wastewater treatment plants are not able to remove them efficiently. Laccases are promising enzymes for bioremediation because they can oxidize a wide variety of substrates. The aim of this study was to evaluate the Botrytis aclada laccase for the oxidation of chlortetracycline and its isomers in the absence of a mediator molecule, at a pH range between 3.0 to 7.0, and to characterize the transformation products by LC-MS. Chlortetracycline and three isomers were detected in both, controls and reaction mixtures at 0 h and in controls after 48 h of incubation but in different proportions depending on pH. An additional isomer was also detected, but only in the presence of BaLac. Based on the transformation products identified in the enzymatic reactions and information from literature, we assembled a network of transformation pathways starting from chlortetracycline and its isomers. The spectrometric analysis of the products indicated the probable occurrence of oxygen insertion, dehydrogenation, demethylation and deamination reactions. Four new products were identified, and we also described a novel transformation product without the chloro group. We observed that increasing pH led to higher diversity of main products. This is the first study using the laccase from fungi Botrytis aclada to oxidate chlortetracycline and its isomers and it can be considered as an ecological alternative to be used in bioremediation processes such as wastewater.

Controlled environments are pivotal in all bioconversion processes, influencing the efficacy of biocatalysts. In this study, we designed a batch bioreactor system with a packed immobilization column and a decontamination chamber to enhance phenol and 2,4-dichlorophenol degradation using the hyper-tolerant bacterium Pseudomonas aeruginosa STV1713. When free cells were employed to degrade phenol and 2,4-DCP at a concentration of 1000 mg/L, the cells completely removed the pollutants within 28 h and 66 h, respectively. Simultaneous reductions in chemical oxygen demand and biological oxygen demand were observed (phenol: 30.21 mg/L/h and 16.92 mg/L/h, respectively; 2,4-dichlorophenol: 12.85 mg/L/h and 7.21 mg/L/h, respectively). After assessing the degradation capabilities, the bacterium was immobilized on various matrices (sodium alginate, alginate-chitosan-alginate and polyvinyl alcohol-alginate) to enhance pollutant removal. Hybrid immobilized cells exhibited greater tolerance and degradation capabilities than those immobilized in a single matrix. Among them, polyvinyl alcohol-alginate immobilized cells displayed the highest degradation capacities (up to 2000 mg/L for phenol and 2500 mg/L for 2,4-dichlorophenol). Morphological analysis of the immobilized cells revealed enhanced cell preservation in hybrid matrices. Furthermore, the elucidation of the metabolic pathway through the catechol dioxygenase enzyme assay indicated higher activity of the catechol 1,2-dioxygenase enzyme, suggesting that the bacterium employed an ortho-degradation mechanism for pollutant removal. Additionally, enzyme zymography confirmed the presence of catechol 1,2-dioxygenase, with the molecular weight of the enzyme determined as 245 kDa.

Environmental pollution caused by petrochemical hydrocarbons (HC) and plastic waste is a pressing global challenge. However, there is a promising solution in the form of bacteria that possess the ability to degrade HC, making them valuable tools for remediating contaminated environments and effluents. Moreover, some of these bacteria offer far-reaching potential beyond bioremediation, as they can also be utilized to produce polyhydroxyalkanoates (PHAs), a common type of bioplastics. The accumulation of PHAs in bacterial cells is facilitated in environments with high C/N or C/P ratio, which are often found in HC-contaminated environments and effluents. Consequently, some HC-degrading bacteria can be employed to simultaneously produce PHAs and conduct biodegradation processes. Although bacterial bioplastic production has been thoroughly studied, production costs are still too high compared to petroleum-derived plastics. This article aims to provide a comprehensive review of recent scientific advancements concerning the capacity of HC-degrading bacteria to produce PHAs. It will delve into the microbial strains involved and the types of bioplastics generated, as well as the primary pathways for HC biodegradation and PHAs production. In essence, we propose the potential utilization of HC-degrading bacteria as a versatile tool to tackle two major environmental challenges: HC pollution and the accumulation of plastic waste. Through a comprehensive analysis of strengths and weaknesses in this aspect, this review aims to pave the way for future research in this area, with the goal of facilitating and promoting investigation in a field where obtaining PHAs from HC remains a costly and challenging process.