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From 13C-Lignin to 13C-Mycelium: Agaricus bisporus Uses Polymeric Lignin as a Carbon Source

Summary

This groundbreaking research shows that the common button mushroom (Agaricus bisporus) can use lignin, a tough plant polymer, as a food source – something previously thought impossible. The fungus breaks down lignin and converts it into proteins and other cellular components, challenging our understanding of how fungi interact with plant materials. Impacts on everyday life: • Offers new ways to recycle plant waste materials into valuable products • Helps explain how mushrooms contribute to natural decomposition in forests • Could lead to more sustainable mushroom cultivation methods • May enable development of new eco-friendly industrial processes • Improves our understanding of carbon cycling in nature

Background

Plant biomass conversion by saprotrophic fungi plays a pivotal role in terrestrial carbon cycling. The general consensus has been that fungi metabolize carbohydrates, while lignin is only degraded and mineralized to CO2. However, recent research demonstrated fungal conversion of 13C-monoaromatic compounds into proteinogenic amino acids, challenging this paradigm.

Objective

To unambiguously prove that polymeric lignin is not merely degraded but also metabolized by fungi, using carefully isolated 13C-labeled lignin as a substrate for Agaricus bisporus, the world’s most consumed mushroom. The study aimed to determine if A. bisporus could assimilate and metabolize lignin when offered as a carbon source.

Results

A. bisporus formed a dense mycelial network, secreted lignin-active enzymes, depolymerized, and removed lignin with a carbon use efficiency of 0.14 (g/g). The fungal biomass showed significant 13C-enrichment, particularly in amino acids, while fungal-derived carbohydrates, fatty acids, and ergosterol showed traces of 13C. The study demonstrated that A. bisporus could assimilate and metabolize lignin via aromatic ring-cleaved intermediates to central metabolites.

Conclusion

The research conclusively demonstrates that A. bisporus can use polymeric lignin as a carbon source for biomass formation, particularly for protein synthesis. This finding challenges the long-standing paradigm that lignin is only degraded and not metabolized by fungi, opening new possibilities for biotechnological valorization of lignin and deepening our understanding of terrestrial carbon cycling.
  • Published in:Science Advances,
  • Study Type:Laboratory Experimental Study,
  • Source: 10.1126/sciadv.adl3419
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