Carbon flow in Agaricus bisporus compost: a stable isotope biomarker study
Dam, F. van
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The white button mushroom, Agaricus bisporus, is commercially produced on compost. The interaction between A. bisporus and the microbiota in the compost was examined using stable isotope techniques and phospholipid derived fatty acids (PLFAs) . Microcosms were constructed with phase II-end compost and different fungal and bacterial densities: industry standard fungal density, low fungal density, low bacterial density (autoclaved compost), and compost without A. bisporus spawn. 13C labelled glucose was added to track the transfer of carbon from the compost into the microorganisms and CO2 over 24-day incubation. A parallel experiment with different fungal densities was run in which additional 13C labelled glucose was added at day 14 to alleviate any substrate limitation. The results showed that A. bisporus suppresses bacteria in the compost, with only 33.1% ± 6.8% and 27.3% ± 4.8% of initial bacterial biomass present after 24 days for different fungal densities, whereas in absence of A. bisporus the bacterial biomass increased with 127% ± 4.6%. However, low bacterial density compost did not significantly reduce the growth of A. bisporus (17 ± 6.8 mg mycelium g¯¹ compost) when compared to non-autoclaved compost (12 ± 1 mg mycelium g¯¹ compost). The composition of the bacterial community changed when A. bisporus was present, with a relative increase in activity of Gram- bacteria compared to Gram+ bacteria over time. There was little indication that the growth of A. bisporus is restricted by carbon limitation.