The growth of proteolytic microorganisms affects keratinolytic fungi in sewage sludge

The present study was to demonstrate the effect of proteolytic microorganisms on the growth and composition of keratinolytic fungi in sewage sludge. In model experiments, the 3-layer hair baiting method (layer I--sludge solidified with agar medium; layer II--agar medium layer covering layer I; and layer III--hair) was used. The agar medium contained increasing peptone concentrations (0, 0.5, 1, 2, 5 and 10 g/L). The number of occurrences along with other fungal growth indices increased up to the peptone concentration of 2 g/L. Upon the highest peptone concentration (10 g/L), the abundant growth of sludge proteolytic bacteria and fungi inhibited the growth of most keratinolytic fungi. Under these conditions, only Scopulariopsis brevicaulis, the fungus of epidemiological concern, was able to penetrate the medium and to attack hair. The antibiotics (chloramphenicol and actidione in concentrations of 100 and 500 mg/L) added to the peptone agar inhibited, to a high degree, the growth of sludge proteolytic microbiota and enabled many keratinolytic fungi to grow.