Variations in lignin monomer contents and stable hydrogen isotope ratios in methoxy groups during the biodegradation of garden biomass

Abstract

Lignin, a highly polymerized organic component of plant cells, is one of the most difficult aromatic substances to degrade. Selective biodegradation under mild conditions is a promising method, but the dynamic variations in lignin monomers during the biodegradation of lignocellulose are not fully understood. In this study, we evaluated the differences in lignin degradation under different microbial inoculation based on the lignin monomer content, monomer ratio, and stable hydrogen isotope ratio of lignin methoxy groups (δ2HLM). The weight loss during degradation and the net loss of lignocellulosic components improved dramatically with fungal inoculation. Syringyl monolignol (S-lignin), which contains two methoxy groups, was more difficult to degrade than guaiacyl (G-lignin), which contains only one methoxy group. The co-culture of Pseudomonas mandelii and Aspergillus fumigatus produced the greatest decrease in the G/S ratio, but δ2HLM values did not differ significantly among the three biodegradation experiments, although the enrichment was done within the fungal inoculation. The fluctuation of δ2HLM values during the initial phase of biodegradation may be related to the loss of pectic polysaccharides (another methoxy donor), which mainly originate from fallen leaves. Overall, the relative δ2HLM signals were preserved despite decreasing G/S ratios in the three degradation systems. Nevertheless, some details of lignin δ2HLM as a biomarker for biogeochemical cycles need to be explored further.

Ganoderma lucidum bran-derived blue-emissive and green-emissive carbon dots for detection of copper ions

“…The synthesis of multicolor fluorescent CDs from biomass is still an exciting research field. 34,35 The main component of biomass is lignin, which has the perfect robustness that comes from its remarkable and compact morphology structure. This particular structure makes lignin difficult to pyrolysis, limiting its deep development and utilization.…”

Effects of Climate Change on Soil Organic Matter C and H Isotope Composition in a Mediterranean Savannah (Dehesa): An Assessment Using Py-CSIA

“…Two feasible explanations are found for these isotopic differentiation of lignin units: (1) n the first place, these methoxyphenols are produced through a more direct pathway of incorporation in growing biomass; (2) their biodegradation rate as part of SOM led to an enrichment of residual substrates . Since preferential complex enzymatic reactions have taken place because of indirect changes in microbial dynamics, hence the lighter isotopes can be more easily utilized by microbes …”

“…94 Since preferential complex enzymatic reactions have taken place because of indirect changes in microbial dynamics, hence the lighter isotopes can be more easily utilized by microbes. 95 Ultimately, biomarker data comprising alkyl and lignin SOM compounds suggest that climatic treatments effectively resulted in a change in ecosystem hydrology causing enriched δ 2 H values as found in the W+D treatment in the tree habitat. Despite the fact that it could be hypothesized that the drought effect could be buffered under the tree canopy, it has been proved that under the tree canopy, the combined effect of warming and drought is more intense compared to that in open grassland.…”

“…36 Among these, nonexchangeable H of n-alkanes and lignin methoxyphenols can enlighten processes related to paleoclimatic reconstruction, 37 SOM degradation processes, 38 and source vegetation and origin. 21,39 Uncertainties in the turnover of SOM compounds hinder the implementation of innovative analytical techniques for elucidating this topic. There are several wide fingerprinting tools that could be applied in SOM characterization, such as conventional analytical pyrolysis gas chromatography/mass spectrometry (Py-GC/MS) 19,40 and isotope ratio mass spectrometry (IRMS).…”

“…Although it is known that some compound such as waxes and long-chain alkanes are isotopically unchangeable during biodegradation, other studies have reported that different biomarkers can exhibit distinct patterns of carbon isotopic fractionation during biodegradation experiments. , On the other hand, H has various molecular forms in soil, determining its organic or inorganic form and how it can be exchanged with ambient water vapor; , H covalently bound to C in organic molecules is considered stable and nonexchangeable . Among these, nonexchangeable H of n -alkanes and lignin methoxyphenols can enlighten processes related to paleoclimatic reconstruction, SOM degradation processes, and source vegetation and origin. , …”