Protein extraction and enzymatic hydrolysis of ammonia-treated cassava leaves (Manihot esculenta Crantz).
In the present work, cassava leaves were treated with 0.5 kg ammonia/kg dry matter at 78 degrees C and 30% moisture content in a 2-kg reactor. Protein extraction was carried out with a calcium hydroxide solution (pH 10) for 30 min at several temperatures (30 degrees C, 45 degrees C, 60 degrees C, 75 degrees C, and 90 degrees C) and solid/liquid ratios (1:10 and 1:15) in a thermostatized bath. Soluble protein content of the extracts was determined by Lowry's method. Dry substrate concentrations of 5%, 7.5%, and 10% and enzyme doses of 2 and 5 IU/g dry matter were used for the enzymatic hydrolysis in an orbital incubator at 50 degrees C and 100 rpm. Both cellulase and xylanase were used. Reducing sugars produced were determined with the 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 degrees C with a 1:10 solid/liquid ratio. The concentrate had a protein content of 36.35% and the amino acid profile was suitable for swine and poultry. The highest sugar yield was 54.72% with respect to theoretical and was obtained with 5% solids and an enzyme dose of 5 IU/g dry matter. This yield was 3.4 times higher than the yield of the untreated leaves (16.13%). These results indicate that cassava leaves have a great potential for animal feeding and ethanol production. Both protein extraction and sugar yields may be enhanced by optimizing the ammonia treatment.
Urribarrí
Lauris
L
Chemistry Department, Science Faculty, University of Zulia, Maracaibo, Venezuela.
Chacón
David
D
González
Orlaidy
O
Ferrer
Alexis
A
D000641:Ammonia / Q000737:chemistry*; D001709:Biotechnology / Q000379:methods*; D002365:Manihot / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry* / Q000302:isolation & purification*; D013696:Temperature
D010940:Plant Proteins; D000641:Ammonia