Retention of fungal enzyme activity in environmental liquid and filter samples.

Fungal biomass can be determined by measuring the beta-N-acetylhexos-aminidase (NAHA) enzyme activity. NAHA, an enzyme present in fungal mycelium and spores, has been detected in inactive, dormant and non-viable cells. Very little information is available on the enzyme activity of different species or retention of the activity under various storage conditions. This study used fluorometry to evaluate the enzyme activity of liquid and filter samples containing spores of four fungal species from genera Penicillium, Cladosporium, Aspergillus, and Acremonium. When fungal spores were stored on a filter, enzyme activity was more stable than when the spores were maintained in suspension for one year. The enzyme activity in suspension samples increased with most of the differences detected between the values at the baseline and 12 months being statistically significant. The results indicate that enzyme activity varies between species. Cladosporium spores had highest NAHA content per spore, whereas Acremonium did not exhibit any detectable enzyme activity even when viability was detected. The results indicated that samples should be stored as dry filter samples.