# Edible Fungi Are a Hidden Source of Carbon Monoxide and Carbon Dioxide

## TL;DR

Edible mushrooms like shiitake can produce carbon monoxide and carbon dioxide during their growth, independent of bacteria or oxygen levels.

## Contribution

This is the first evidence that edible fungi generate CO as part of their metabolism, without bacterial involvement.

## Key findings

- CO emissions from fungi followed a parabola-shaped curve, peaking during full mycelial colonization.
- Shiitake mushrooms on birch substrate emitted the highest CO compared to other substrates and species.
- Fungal respiration contributes more to CO dynamics than previously recognized.

## Abstract

This study provides the first clear evidence that edible mushrooms, such as Lentinula edodes (shiitake), Pleurotus ostreatus and Pleurotus eryngii
, can generate carbon monoxide (CO) as part of their metabolic activity—independent of bacteria, illumination or oxygen limitation. Systematic measurements of CO and CO2 emissions were performed over 60 days using multiple fungal species, substrates and growth conditions. Microscopy observations (light, scanning and transmission electron microscopy) confirmed no extracellular and intracellular bacterial endosymbionts involved, supporting a fungal genesis of CO. CO emission patterns showed a parabola‐shaped curve, correlating with CO2 levels regardless measurements by gas‐analyser or GC–MS and peaking during full mycelial colonisation. Shiitake mushrooms grown on birch substrate released the highest CO compared to alder and aspen substrates and P. ostreatus and P. eryngii
. These findings suggest that fungal respiration contributes to CO dynamics more than previously recognised and highlight the need for further research into its mechanisms and environmental and occupational health implications.

This study provides the first and robust evidence that edible mushrooms, such as Lentinula edodes, Pleurotus ostreatus and
P. eryngii
, can generate carbon monoxide (CO) as part of their metabolic activity—independent of bacteria, illumination or oxygen limitation. This is largely different from what was previously recognised. The findings resulted from systematic measurements of CO and CO2 emissions over 60 days using multiple fungal species, substrates and growth conditions in nine experiments.