Protein enrichment of sweet potato residue with amylolytic yeasts by solid-state fermentation

Starchy agricultural wastes were inoculated with amylolytic yeasts for protein enrichment by solid-state fermentation. The moisture content of substrate was 65-69%, and water activity was equivalent to 0.98-0.99. The optimum conditions for protein enrichment were initial moisture content 65%, initial pH 4.5, a 1:1 mixture of ammonium sulfate and urea was incrementally added to the ferment with 1% added at zero time, 1% added at 24 h, and 0.5% added at 48 h, and incubation with amylolytic yeasts (1.0 x 10(10)/100 g substrate) at 30 degrees C for 2-3 days. The final product contained 16.11-20.82% protein.