4-MUF-NAG for fungal biomass determination: Scope and limitations in the context of biodeterioration studies

In the field of biodeterioration of cultural heritage by fungi, quantification of fungal growth is a regularly required procedure. Recently, a fluorometric method for detection and estimation of fungal growth using 4-methylumbelliferyl-N-acetyl-β-D-glucosaminide (4-MUF-NAG) was proposed. In order to evaluate the potentials and limitations of this method for fungal biomass quantification, different experimental conditions to develop calibration curves were tested, using Aspergillus niger, Cladosporium cladosporioides, Chaetomium globosum and Penicillium chrysogenum fungal strains. The results showed that the correlation between fluorescence and biomass differs according to fungal species and stage of growth. Therefore, a measurement of fluorescence may not be indicative of a specific value of biomass. Also, false positive and negative results for fungal growth can be obtained. C. globosum was the fungal species that showed the most constant correlation between biomass and fluorescence throughout the different incubation periods.