Impact of environmental factors on fungal respiration and dry matter losses in wheat straw.
An automatic electrolytic respirometer enabled replicated determinations of the respiration rates of individual fungi on sterile straw, and the mixed mycoflora of naturally contaminated wheat straw at different steady-state temperatures (10-30 degrees C) and water activities (a(w), 0.75-0.98) over periods of 8-14 days. Generally, the respiratory activity of individual spoilage fungi (Alternaria alternata, Cladosporium cladosporioides, Eurotium amstelodami, Fusarium culmorum and Penicillium aurantiogriseum) on sterile wheat straw increased linearly with increasing a(w) at 25 degrees C. The calculated maximum dry matter loss of wheat straw due to colonisation by individual species was about 10%, regardless of a(w). On naturally contaminated wheat straw fungal activity was also related to temperature and a(w), with maximum respiration at 30 degrees C and 0.98 a(w). At the lowest temperature examined, 10 degrees C, there was a slight lag prior to respiratory activity occurring. The respiratory activity was also significantly reduced (by half) when available water was reduced to 0.95-0.90 a(w). In contrast to the colonisation of sterile straw by individual species, the maximum dry matter loss caused by fungal deterioration of naturally contaminated wheat straw was 3.4% at 0.98 a(w) and 30 degrees C. The dominant fungal genera and species varied with a(w) and temperature. These results are discussed in relation to the storage of cereal straw without spoilage.
Willcock
J
Applied Mycology Group, Cranfield Biotechnology Centre, Cranfield University, Cranfield, Bedford MK43 0AL, UK
Magan
N