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<p>Microbial degradation of refractory dissolved organic matter (RDOM) plays a crucial role in maintaining lake ecosystem balance, yet its underlying mechanisms remain poorly understood. This study employed methods such as scanning electron microscopy-energy dispersion spectrometry, gel permeation chromatography, gas chromatography-mass spectrometry, and absorption spectroscopy to explore the degradation mechanisms of <i>Novosphingobium</i> sp. THN1 strain on kraft lignin (representing RDOM) and lake water samples. The results showed that <i>Novosphingobium</i> sp. THN1 reduced the total organic carbon of kraft lignin by 53.46% within 72&#xa0;h through the synergistic action of manganese peroxidase, lignin peroxidase and laccase. After degradation, the C/O ratio of kraft lignin decreased from 0.71 to 0.37, indicating the occurrence of REDOX reactions. The disappearance of substances above 7000 Da and the emergence of substances below 1500 Da indicate the transformation of kraft lignin into small-molecule substances. Through degradation product analysis, a four-step degradation mechanism was identified: initial depolymerization to dimers, bond cleavage to phenylpropane monomers, oxidation to intermediates, and finally benzene ring cleavage to aliphatic compounds. The analysis revealed the transformation pathways of both common and rare phenylpropane monomers, with final products entering the TCA cycle for complete mineralization. This comprehensive mechanistic understanding demonstrates the complete degradation pathway from complex lignin polymers to simple metabolic intermediates. Notably, this degradation pattern was consistently observed in both kraft lignin and lake water samples. This novel mechanistic insight into RDOM transformation provides valuable guidance for improving water treatment strategies and lake ecosystem management.</p>

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Degradation Pathways of Kraft Lignin by Novosphingobium sp. THN1: Insights into Refractory Dissolved Organic Matter Transformation in Lake Ecosystems

  • 期刊论文

  • 发表日期：

    2026年2月5日

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  • Chenyang Deng,
  • Liwen Zhang,
  • Chun Qing,
  • Yuange Yu,
  • Haorui Zhao,
  • Genyi Wu,
  • Yiqing Lin

摘要

Microbial degradation of refractory dissolved organic matter (RDOM) plays a crucial role in maintaining lake ecosystem balance, yet its underlying mechanisms remain poorly understood. This study employed methods such as scanning electron microscopy-energy dispersion spectrometry, gel permeation chromatography, gas chromatography-mass spectrometry, and absorption spectroscopy to explore the degradation mechanisms of Novosphingobium sp. THN1 strain on kraft lignin (representing RDOM) and lake water samples. The results showed that Novosphingobium sp. THN1 reduced the total organic carbon of kraft lignin by 53.46% within 72 h through the synergistic action of manganese peroxidase, lignin peroxidase and laccase. After degradation, the C/O ratio of kraft lignin decreased from 0.71 to 0.37, indicating the occurrence of REDOX reactions. The disappearance of substances above 7000 Da and the emergence of substances below 1500 Da indicate the transformation of kraft lignin into small-molecule substances. Through degradation product analysis, a four-step degradation mechanism was identified: initial depolymerization to dimers, bond cleavage to phenylpropane monomers, oxidation to intermediates, and finally benzene ring cleavage to aliphatic compounds. The analysis revealed the transformation pathways of both common and rare phenylpropane monomers, with final products entering the TCA cycle for complete mineralization. This comprehensive mechanistic understanding demonstrates the complete degradation pathway from complex lignin polymers to simple metabolic intermediates. Notably, this degradation pattern was consistently observed in both kraft lignin and lake water samples. This novel mechanistic insight into RDOM transformation provides valuable guidance for improving water treatment strategies and lake ecosystem management.