Protopectinases (PPases) are a heterogeneous group of enzymes that release water-soluble pectin from insoluble protopectin in plant tissues by restricted degradation of the substrate, In all experiments reported to date, PPases of bacterial or yeast origin were produced in liquid culture, Here, we described the growth and enzyme production of Aspergillus awamori IFO 4033 in solid-state culture at three acidities, Petri dishes containing 10 g of wheat bran and 15 mi of 0.2, 0.3, or 0.4 N HCl were inoculated with 2 mi of a suspension of 10(5) spores/ml and incubated for 48 h at 30 degrees C. When 0.2 N HCl was used, PPase activity on lemon (PPase-l) and apple (PPase-a) protopectins was maximum at 24 h of culture (1,490 and 610 U/g, respectively), With 0.3 and 0.4 N HCl, the PPase activity was highest at 36 h (1,460 and 950 PPase-l U/g, and 400 and 310 PPase-a U/g, respectively). Whatever the acidity, polygalacturonase and pectinase activities were maximum at 48 h, Hence, the crude enzyme pool obtained at an early stage of culture was appropriate for extraction of citrus and apple pectin, The ratio of PPase-l to PPase-a changed during culture and the acidity affected this ratio, so there seemed to be at least two PPases with different substrate specificities.