Elucidation of the coumarin degradation by Pseudomonas sp. strain NyZ480

Detoxification of coumarins by rumen anaerobic fungi: insights into microbial degradation pathways and agricultural applications

BACKGROUND

Coumarins are toxic phytochemicals found in a variety of plants and are known to limit microbial degradation and interfere with nutrient cycling. While the degradation of coumarins by fungi has been studied in an environmental context, little is known about their degradation in the gastrointestinal system of herbivores after ingestion.

RESULTS

In this study, we investigated in vitro fermentation by microbial enrichment, transcriptome sequencing, and high-resolution mass spectrometry to evaluate the ability of rumen anaerobic fungi to degrade coumarins. The results showed that despite the low abundance of anaerobic fungi in the rumen microbiota, they were able to effectively degrade coumarins. Specifically, Pecoramyces ruminantium F1 could tolerate coumarin concentrations up to 3 mmol/L and degrade it efficiently via metabolic pathways involving alpha/beta hydrolases and NAD(P)H oxidoreductases within the late growth phase. The fungus metabolized coumarin to less toxic compounds, including o-coumaric acid and melilotic acid, highlighting the detoxification potential of anaerobic fungi.

CONCLUSIONS

This study is the first to demonstrate the ability of rumen anaerobic fungi to degrade coumarin, providing new insights into the use of anaerobic fungi in sustainable agricultural practices and environmental detoxification strategies.

Elucidating the role of the genus Pseudomonas involved in coumarin degradation

Coumarin, a synthetic chemical and phytotoxin, exhibits hepatotoxicity and carcinogenicity, posing threats to both human health and environmental safety. Microbial degradation effectively mitigates environmental contamination. In this study, a coumarin-degrading bacterial consortium designated as XDS-7 with Pseudomonas as the key degrader was obtained. However, there is a lack of comprehensive perspective on the key role of the genus Pseudomonas involved in coumarin degradation. We employed the consortium XDS-7 as a model system to investigate the critical role of the genus Pseudomonas involved in coumarin degradation. Metagenomic binning analysis indicated that bin 14 (Pseudomonas sp.) contains the full complement of genes required for coumarin degradation. A coumarin-degrading bacterium, Pseudomonas sp. strain X4, was isolated from consortium XDS-7 using a traditional enrichment method supplemented with chloramphenicol. Genomic analysis demonstrated that strain X4 carries a suite of genes to completely degrade coumarin. Bioinformatics analysis revealed that putative coumarin-degrading bacteria are widely distributed across diverse bacteria of the genus Pseudomonas. In addition, strain X4 completely removed 100 mg kg-1 of coumarin from contaminated soil within 48 h and 100 mg L-1 of coumarin from contaminated wastewater within 4 h. This study will greatly enhance our understanding and utilization of these valuable bioresources.

One-component anti-aging agents

Polymer photo-oxidation aging is a significant issue in plastics engineering, leading to reduced performance, shorter lifespan, and additional pollution. Anti-aging agents, including antioxidants and ultraviolet (UV)-shielding agents, are used to ameliorate the above problems. However, multi-component agents involve complex synthesis, mixed processing, and environmental concerns. Therefore, developing robust, multi-functional, one-component anti-aging agents is crucial. This study proposed a new class of one-component poly(coumarin) anti-aging agents, synthesized through enzymatic polymerization of coumarin. These agents exhibited a broader UV absorption spectrum and higher antioxidative capacity than commercial UV-shielding agent UV326 and antioxidant AO1010. Calculating the O-H bond dissociation energy and reaction energy barrier with peroxy free radicals (ROO˙) showed that the material could effectively attenuate UV radiation and scavenge free radicals, improving anti-aging properties. Further studies indicated the potential of poly(coumarin) anti-aging agents for enhanced polymer photostability and improved food preservation packaging. Consequently, poly(coumarin) nanoparticles can act as versatile anti-aging compounds, potentially replacing conventional multi-component agents and providing a new foundation for one-component materials with multiple functions.

Fabrication of a biochar-doped monolithic adsorbent and its application for the extraction and determination of coumarins from Angelicae Pubescentis Radix

A monolithic adsorbent was designed aiming to the structure of osthole and columbianadin, and fabricated using diallyl phthalate as the monomer and ethylene dimethacrylate as the crosslinker with the addition of bamboo biochar, via polymerization reaction in a stainless-steel tube. The prepared composite adsorbent packed in the tube was used as a solid-phase extraction column for the extraction and determination of two coumarins (osthole and columbianadin) in Angelicae Pubescentis Radix, combing with a C18 analytical column through an HPLC instrument, which show excellent matrix-removal ability and good selectivity to osthole and columbianadin. Furthermore, the present adsorbent shows good applicability, which was used for the extraction of osthole from Duhuo Jisheng Pill. Compared to the commercial C18 and phenyl adsorbent, the present adsorbent own better selectivity and higher resolution. These results attributed to the enhanced specific surface area (141 m2/g) and enriched interaction sites of the resulting composite adsorbent, due to the doping of bamboo biochar, which can produce hydrogen bond, dipole-dipole, π-π and hydrophobic force interactions with the osthole and columbianadin. The methodology validation indicated that the present method showed good precision and good accuracy, and the composite adsorbent showed good preparative repeatability, which can be reused for no less than 100 times with the relative standard deviation ≤4.6 % (n = 100). The present work provided a simple and efficient method for the extraction and determination osthole and columbianadin from Angelicae Pubescentis Radix.

Redundant and scattered genetic determinants for coumarin biodegradation in Pseudomonas sp. strain NyZ480

Coumarin (COU) is both a naturally derived phytotoxin and a synthetic pollutant which causes hepatotoxicity in susceptible humans. Microbes have potentials in COU biodegradation; however, its underlying genetic determinants remain unknown. Pseudomonas sp. strain NyZ480, a robust COU degrader, has been isolated and proven to grow on COU as its sole carbon source. In this study, five homologs of xenobiotic reductase A scattered throughout the chromosome of strain NyZ480 were identified, which catalyzed the conversion of COU to dihydrocoumarin (DHC) in vitro. Phylogenetic analysis indicated that these COU reductases belong to different subgroups of the old yellow enzyme family. Moreover, two hydrolases (CouB1 and CouB2) homologous to the 3,4-dihydrocoumarin hydrolase in the fluorene degradation were found to accelerate the generation of melilotic acid (MA) from DHC. CouC, a new member from the group A flavin monooxygenase, was heterologously expressed and purified, catalyzing the hydroxylation of MA to produce 3-(2,3-dihydroxyphenyl)propionate (DHPP). Gene deletion and complementation of couC indicated that couC played an essential role in the COU catabolism in strain NyZ480, considering that the genes involved in the downstream catabolism of DHPP have been characterized (Y. Xu and N. Y. Zhou, Appl Environ Microbiol 86:e02385-19, 2020) and homologous catabolic cluster exists in strain NyZ480. This study elucidated the genetic determinants for complete degradation of COU by Pseudomonas sp. strain NyZ480.IMPORTANCECoumarin (COU) is a phytochemical widely distributed in the plant kingdom and also artificially produced as an ingredient for personal care products. Hence, the environmental occurrence of COU has been reported in different places. Toxicologically, COU was proven hepatotoxic to individuals with mutations in the CYP2A6 gene and listed as a group 3 carcinogen by the International Agency for Research on Cancer and thus has raised increasing concerns. Until now, different physicochemical methods have been developed for the removal of COU, whereas their practical applications were hampered due to high cost and the risk of secondary contamination. In this study, genetic evidence and biochemical characterization of the COU degradation by Pseudomonas sp. strain NyZ480 are presented. With the gene and strain resources provided here, better managements of the hazards that humans face from COU could be achieved, and the possible microbiota-plant interaction mediated by the COU-utilizing rhizobacteria could also be investigated.