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Fate of Carbohydrates and Lignin During Composting and Mycelium Growth of Agaricus Bisporus on Wheat Straw Based Compost

Summary

This research investigated how button mushroom (Agaricus bisporus) mycelium breaks down and modifies wheat straw during the composting process used in commercial mushroom cultivation. The study revealed that mushroom mycelium has a remarkable ability to break down lignin, a tough plant component that typically resists degradation. This finding has implications beyond mushroom farming, potentially benefiting various applications involving plant biomass processing. Impacts on everyday life: • Improved understanding of mushroom cultivation could lead to more efficient commercial mushroom production • Insights into lignin degradation could help develop better methods for processing plant waste materials • The findings could contribute to developing more sustainable processes for converting agricultural waste into useful products • Understanding how mushrooms break down plant matter could lead to innovations in natural recycling processes • This research may help develop new approaches for producing biofuels and other materials from plant waste

Background

Wheat straw based compost is used for growing Agaricus bisporus mushrooms, containing about 57% carbohydrates (mostly cellulose and xylan) and 27% lignin. The composting process aims to make these components more accessible as a carbon source for mushroom growth, but the extent of changes in the carbohydrate-lignin matrix during composting and mycelium growth was previously unknown.

Objective

To conduct a detailed mass balance analysis of dry matter, proteins, cellulose, xylan, lignin and ash during the composting process and mycelium growth of Agaricus bisporus. Additionally, to study the structural changes of xylan and lignin throughout these phases.

Results

During Phase II of composting, 50% of both xylan and cellulose were metabolized by microbial activity, while lignin structures remained unaltered. During A. bisporus mycelium growth (Phase III), carbohydrates were only slightly consumed and xylan was partially degraded. Significantly, 45% of lignin was metabolized during mycelium growth based on pyrolysis GC/MS analysis. The remaining lignin showed structural modifications with an increase in syringyl to guaiacyl (S:G) ratio from 0.5 to 0.7, and fewer decorations remained on the phenolic skeleton of both S and G units.

Conclusion

The study demonstrated that major changes in carbohydrate content occur during Phase II composting, while significant lignin modification happens during mycelium growth. A. bisporus was shown to metabolize 45% of lignin and modify remaining lignin structures by removing decorations and increasing the S:G ratio. This research provides new insights into how A. bisporus degrades lignocellulosic biomass during mushroom cultivation.
  • Published in:PLoS One,
  • Study Type:Experimental Research,
  • Source: 10.1371/journal.pone.0138909
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