Leaf Protein from Ammonia-Treated Dwarf Elephant Grass (<I>Pennisetum purpureum</I> Schum cv. Mott)

Abstract

Proteins can be an excellent byproduct of the biorefining of lignocellulosic materials. In this work, extraction conditions for the white leaf proteins (cytoplasmic) of ammonia-treated dwarf elephant grass were established to obtain a protein juice suitable for the production of leaf protein concentrates. A calcium hydroxide solution was used as extracting agent, at several solid-liquid ratios, pHs, temperatures, and times. Extractions were carried out in Erlenmeyer flasks containing 5 g (dry basis) of forage with constant agitation (100 rpm). The soluble protein content was determined by the Lowry method. Optimal extraction conditions for the ammonia-treated forage were 12.60 pH, 1:10 solid-liquid ratio, 90 degrees C, and 30 min extraction time, resulting in 52.65% extraction yield. The ammonia treatment significantly increased (p<0.05) the release of proteins from the fibrous matrix, facilitating their extraction.

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

“…The greatest yield for white protein extraction was 29.1%, which is 1.5-fold the extraction yield of untreated leaves, 20%. Both yield and increase in protein extraction are relatively low compared with those obtained for grasses such as dwarf elephant grass, 52.65% and 4.5-fold, respectively [5], which may be due to the higher lignin content of the cassava leaves (16.78% for cassava leaves relative to 4% for dwarf elephant grass), which suggest that treatment should be more severe, although it could damage the protein. It is important to point out that white protein content in the leaf is usually around 50% of the total protein, which indicates that the extraction of the white protein could have reached 60% of the initial content of white protein for ammonia-treated leaves.…”

“…Changes caused by alkali treatments involve breakage of ester linkages and opening of the crystalline structure of the cellulose [18]. Protein Extraction Figure 1 shows the yields of the proteins extracted at several temperatures and solid/liquid ratios using pH 10 calcium hydroxide solution for 30 min, conditions that were previously determined according to Urribarrí et al [5]. The yield increased as temperature increased.…”

“…All the extractions were carried out in triplicate with 5 g of dry matter with constant stirring, varying solid/ liquid ratio (1:10, 1:15) and temperature (30°C, 45°C, 60°C, 75°C, and 90°C) for 30 min. Extracts were refrigerated to eliminate green proteins by precipitation [5]. After centrifugation, the white protein (true protein) present in the extracts was determined by the Lowry's modified method [11].The protein extraction yield was determined with respect to initial crude protein content.…”

“…Ammonia treatments have been successful in separating grass proteins from the fibers [5] and removing tannins [6], which increases the potential of the leaves for animal feeding, mainly swine and poultry. In addition, protein extraction leaves a solid fraction rich in cellulose which can be converted into sugars with greater yields [7] and these into ethanol by fermentation.…”

Extraction of Proteins from Switchgrass Using Aqueous Ammonia within an Integrated Biorefinery

“…De la Rosa [17] and Urribarri [18] found increases in protein yields from coastal bermuda grass and dwarf elephant grass, respectively, when undergoing ammonia pretreatment before extraction. By disrupting the lignocellulosic structure of the biomass, proteins appear to more easily diffuse out of the biomass and into solution.…”