Investigation of keratinolytic and non-keratinolytic fungi grown above or below a 1-cm sewage sludge blanket

This study investigated the incidence of keratinolytic and non-keratinolytic fungi grown above or below a 1-cm sewage sludge blanket. The hair baiting method was used. Incubation was carried out at 23 and 37 °C. The number of keratinolytic fungi occurrences below a sludge blanket (anoxic conditions) was almost two times smaller than the number of fungal occurrences above this blanket (oxic conditions). The anoxic conditions did not significantly affect the number of non-keratinolytic fungi. Qualitative differences were also observed. Trichophyton ajelloi with its teleomorph Arthroderma uncinatum and some other fungi were found to prefer oxic conditions. In the case of non-keratinolytic fungi, the most evident differences were observed at 37 °C. Aspergillus fumigatus prevailed above a sludge blanket, while Pseudallescheria boydii was the predominating species below this blanket. The incidence of keratinolytic fungi was dependent on sludge physico-chemical characteristics: mainly on sludge organic matter stabilization (total nitrogen and ammonium nitrogen contents, proteolytic activity and C:N ratio) and hygienization (total and fecal coliforms) factors.