Chemical and physical properties of protein products isolated from chromium-containing leather waste using two consecutive enzymes

The treatment of chrome shavings as a potential source of protein and chromium presents a challenge for more and more researchers from all over the world. Recently, the influence of several different enzymes on the properties of the protein isolated from this waste was investigated, and the effects of pepsin and trypsin were studied and compared because of their noteworthy activities in the process. In this work, the use of two different enzymes in consecutive extractions was studied. The combinations of pepsin-trypsin and pepsin-alkaline protease were evaluated. The shavings were pretreated with pepsin at room temperature and gelatin was extracted with water at 70 degrees C; the chrome sludge recovered after centrifugation then was treated with trypsin or alkaline protease and hydrolysate was extracted at 70 degrees C. The chemical and physical properties of these protein products were evaluated, confirming that a high quality gelatin can be isolated. With a second extraction of hydrolysate, the chrome cake is suitable for chemical treatment before chromium recycling.