( R )-3-amino-1-butanol is a key intermediate of Dolutegravir for the treatment of HIV/AIDS and its green and efficient biosynthesis has attracted a great deal of attention. Transaminases are currently used as promising biocatalyst for the synthesis of chiral amines. However, many transaminases have ( S )-specificity and ( R )-selective transaminases were less exploited and studied, making the production of ( R )-amines remain challenging. In this study, a novel transaminase from Actinobacteria sp. ( As -TA) was obtained and applied for the biosynthesis of ( R )-3-amino-1-butanol by transferring the amino group from isopropylamine to 4-hydroxy-2-butanone. After optimization of the reaction condition and using a substrate fed-batch strategy, the conversion of 100, 200, 300, 400 and 500 mM 4-hydroxy-2-butanone reached 100%, 94.9%, 86.1%, 76.1% and 70.9%, respectively. ( R )-3-amino-1-butanol with a maximum yield of 29.6 g/L and 99.9% e.e. value was obtained. This was the first time demonstrating the successful biosynthesis of ( R )-3-amino-1-butanol with transaminase as biocatalyst and the obtained As -TA enriched the enzyme pool of transaminase with ( R )-specificity.
Polycyclic aromatic hydrocarbons (PAHs) are persistent environmental pollutants threatening soil ecosystems and human health. While soil microbial communities possess intrinsic PAH degradation potential, the dynamics of bacterial populations and degradation-associated genes during natural attenuation remain poorly understood. This study investigated the self-purification capacity of PAH-contaminated soil through a 32-day microcosm experiment using three model PAHs: naphthalene (NAP), phenanthrene (PHE), and pyrene (PYR). Results demonstrated high PAH dissipation rates (94.36 %, 72.60 %, and 47.70 % for NAP, PHE, and PYR, respectively). High-throughput sequencing revealed that PAH exposure (10–100 mg kg −1 ) shifted bacterial community structure, enriching Actinobacterial taxa (Mycobacterium, Rhodococcus, Nocardioides) linked to PAH degradation and strengthening bacterial interactions. Quantitative PCR further indicated substrate-specific gene responses: Actinobacteria harboring nahAC preferentially degraded NAP, while nidA and phe genes were upregulated under PHE/PYR stress. These findings highlight Actinobacteria as keystone degraders and propose leveraging microbial community assembly strategies to optimize bioremediation of PAH-contaminated soils.
Yingying Qian,Houyu Yu,Qihuan He,Dandan Fan,Gerben J. Zylstra,Hancheng Wang,Xing Huang
The extensive application of cyhalofop-butyl, an aryloxyphenoxypropionate (AOPP) herbicide, for weed control in rice fields inevitably results in environmental pollution and ecological toxicity. Microbial degradation of cyhalofop-butyl is garnering immense research attention. This study revealed that Sphingobium yanoikuyae B1 can efficiently degrade the cyhalofop-butyl, completely breaking down 30 mg/L within 12 h via ester bond hydrolysis, forming cyhalofop acid. A novel hydrolase gene cbeH (37.39% identity) was identified in B1. CbeH exhibited catalytic activity by hydrolyzing the ester bond (C-O) in cyhalofop-butyl and other AOPP herbicides, yielding AOPP acids. Additionally, it catalyzed the cleavage of the C-N bond in amide herbicides propanil and diuron, as well as the C-C bond in the aromatic compound 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoic acid. Sequence alignments and site-directed mutagenesis indicated the catalytic triad Ser-His-Asp in CbeH serves as active center cleaving C-O, C-C, and C-N bonds. Comparative analysis revealed the gene cbeH , highly conserved within Sphingomonads , was located within multiple insertion sequences on the plasmid of Rhodococcus strains. CbeH was widespread in Proteobacteria and Actinobacteria, with its host strains prevalent in aromatic-polluted environments. This study provides novel enzyme resources for remediating combined pollution and enhances our understanding of the genetic organization and environmental distribution of trifunctional pollutant-degrading genes.
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