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Caffeine Metabolism During Cultivation of Oyster Mushroom (Pleurotus ostreatus) with Spent Coffee Grounds

Summary

This research investigated how oyster mushrooms grow on used coffee grounds and their ability to break down caffeine. While the mushrooms can grow on coffee waste, caffeine slows their growth. The mushrooms can break down caffeine into other compounds, suggesting potential applications in processing coffee industry waste. The amount of caffeine that remains in the mushrooms is very small – you would need to eat 250 kg of mushrooms to get the caffeine equivalent of one espresso. Impacts on everyday life: • Provides a sustainable way to recycle used coffee grounds • Creates edible mushrooms from waste material • Demonstrates safe consumption of mushrooms grown on coffee waste • Offers potential solutions for coffee industry waste management • Supports development of environmentally-friendly farming practices

Background

In coffee-producing countries, waste products from coffee production serve as useful substrates for cultivating Pleurotus ostreatus (oyster mushroom). This species is relatively easy to grow, coffee waste substrates are readily available, and the mushroom fruiting bodies provide valuable nutrition and income. In developed countries, cultivating P. ostreatus on spent coffee grounds (SCG) from coffee consumption offers a novel approach to recycling this urban waste product.

Objective

To study the effect of spent coffee grounds (SCG) and caffeine on growth of a commercial strain of P. ostreatus in liquid and solid cultures, and on a commercial scale, as well as investigate the mushroom’s ability to metabolize caffeine.

Results

Caffeine inhibited mycelial growth on agar and in liquid culture. Higher levels of SCG in substrate delayed mycelial growth and fruiting. P. ostreatus partially degraded caffeine to xanthine in all SCG-containing substrates, primarily through N-demethylation to theophylline and 3-methylxanthine. Paraxanthine and theobromine were also detected. Caffeine and its metabolites were found in fruiting bodies, though the location of metabolism was unclear.

Conclusion

While P. ostreatus can grow on spent coffee grounds, caffeine inhibits its growth. The mushroom can metabolize caffeine through demethylation pathways. The caffeine content in fruiting bodies is very low – approximately 250 kg of fresh mushrooms would be needed to equal the caffeine in one espresso. While the health impact of caffeine in these mushrooms is minimal, P. ostreatus shows potential for detoxifying coffee production wastes.
  • Published in:Applied Microbiology and Biotechnology,
  • Study Type:Laboratory Research,
  • Source: 10.1007/s00253-019-09883-z
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