Optimized extraction of total proteic mass from water hyacinth dry leaves

Abstract

Optimization and effect simulation of the one-step solid:liquid extraction of the proteic mass from water hyacinth were achieved for glutathione recovery, through a factorial 33 experiment design. The experiment was carried out using dry water hyacinth leaves, previously crushed into a fine powder with particle size not exceeding 0.1 mm, and a sodium phosphate buffer as the extracting phase. For this purpose, 27 attempts were made by varying the dry leaves to buffer w/v ratio (solid:liquid (S/L)), the buffer pH, and extraction time, which are regarded as being key parameters. The total protein mass extracted attained values of 75–76 wt.% of the initial mass of dry hyacinth leaves, at 30 °C, S/L = 1:7.5–1:8.0 and pH 8.2. Time has no influence on the amount of extracted proteins, but a minimum time of 20 min is recommended. The effects of acidity and ionic strength upon protein fractionation were also investigated via potentiometric titrations of the collected extract with citric acid and ammonium sulphate, respectively, in a temperature range (20–60 °C). Most of proteins precipitate at pH 4.5–6.0 in the presence of citric acid and at pH 6.5–5.85 in the presence of ammonium sulphate. Glutathione was detected using high performance liquid chromatography (HPLC) in a liquid fraction after protein precipitation at pH = 5.65 in the presence of ammonium sulphate. Key words: Factorial 33 Design, solid:liquid extraction, water hyacinth, protein separation, optimization, glutathione.