Protein Extraction and Enzymatic Hydrolysisof Ammonia-Treated Cassava Leaves (Manihot esculenta Crantz)

摘要

In the present work, cassava leaves were treated with 0.5 kg ammonia/kg drymatter at 78 °C and 30% moisture content in a 2-kg reactor. Protein extraction was carriedout with a calcium hydroxide solution (pH 10) for 30 min at several temperatures (30 °C,45 °C, 60 °C, 75 °C, and 90 °C) and solid/liquid ratios (1:10 and 1:15) in a thermostatizedbath. Soluble protein content of the extracts was determined by Lowry's method. Drysubstrate concentrations of 5%, 7.5%, and 10% and enzyme doses of 2 and 5 IU/g drymatter were used for the enzymatic hydrolysis in an orbital incubator at 50 °C and 100 rpm.Both cellulase and xylanase were used. Reducing sugars produced were determined withthe dinitrosalicylic acid method. The highest protein extraction yield for, the ammonia-treated leaves was 29.10%, which was 50% higher than with the untreated leaves (20%),and was obtained at 90 °C with a 1:10 solid/liquid ratio. The concentrate had a proteincontent of 36.35% and the amino acid profile was suitable for swine and poultry. Thehighest sugar yield was 54.72% with respect to theoretical and was obtained with 5% solidsand an enzyme dose of 5 IU/g dry matter. This yield was 3.4 times higher than the yield ofthe untreated leaves (16.13%). These results indicate that cassava leaves have a greatpotential for animal feeding and ethanol production. Both protein extraction and sugaryields may be enhanced by optimizing the ammonia treatment.