Mycelial growth and nutritional physiology of zoopathogenic Aspergillus fumigatus FRES., Thermoascus aurantiacus MIEHE, and Thermomyces lanuginosus TSIK., obtained from livestock feeds and poultry droppings in Nigeria were studied. An optimal pH-temperature range of 5.5-6.5 and 37 degrees - 45 degrees C was recorded for the growth of these fungi. Various sources of carbon supplied in the growth medium, except sorbose and rhamnose, were utilized for growth. Only Aspergillus fumigatus caused considerable weight losses of the filter papers supplied and hydrolyzed the carboxy-methyl cellulose (CMC) in the medium. The culture filtrates of this fungus contained CM-cellulases which also hydrolyzed CMC to reducing sugar at 45 degrees C. D-glucose and L-asparagine concentrations in the range of 15-20 g/liter and 2.5-5 g/liter, respectively, were best for growth of the test fungi. Various forms of organic and inorganic nitrogen provided were also utilized. The inorganic sources of nitrogen could readily substitute the organic forms at the optimal growth conditions.

The submerged cultures of Aspergillus nidulans had optimal growth and protease production at 37 degrees C and within 6 days of incubation. A rapid drop in pH of the growth medium from 6.9 to 4.8 and a subsequent gradual rise was recorded with the period of incubation. The acid-protease produced was purified by a combination of ethanolic precipitation, ultrafiltration and fractionation on DEAE-cellulose and Sephadex G-200. A single peak showing protease activity was subsequently obtained with a 16-fold increase in specific activity and a recovery value of 36%. The purified enzyme had optimal activity on casein and gelatin at pH 5.4 and a temperature of 40 degrees C.