Processing of leather waste: Pilot scale studies on chrome shavings. Part I. Isolation and characterization of protein products and separation of chrome cake

During the past years, we have demonstrated that it is possible to isolate protein products from chrome shavings, a waste from the tannery industry, using alkaline protease under mild conditions. This process has been patented and broadly described, though the treatment of the chrome cake has not been described in detail. The objective of this present work was to isolate protein products from chrome shavings, treat and purify the remaining chrome cake and tan hides with the recovered chromium. This first part discusses the digestion of commercial chrome shavings - with an alkali in a first step and with an alkaline protease in a second step - to isolate two different protein products: gelatin and hydrolysate. Chemical and physical properties of these samples were studied. Gelatin samples were deionized and chemical and physical analyses performed. Also, chemical properties of the solid residue from each step of the process were evaluated.