Collagen Hydrolysate Extraction from Chromed Leather Waste for Polymeric Film Production

Abstract

The generation of hazardous wastes and the overuse of nonrenewable sources in polymeric materials production are two major concerns for researchers worldwide. In this paper, an innovative approach to changing chromed leather waste (CLW) into a raw material for polymeric film production was studied. Collagen hydrolysate was extracted from CLW through alkaline hydrolysis. Time, temperature, agitation speed, type and mass of alkalinizing agent were tested. The optimum condition for collagen hydrolysate production (the one that results in a high protein and low chromium content) was determined. According to statistical analysis, hydrolysis performed for 6 h using a proportion of 4 g of MgO for each 50 g of CLW and 250 ml of water at 70°C and 180 rpm of agitation speed led to the best protein/chromium ratio in the collagen hydrolysate (TKN: 2,185.7 mg/L, Cr: <0.04 mg/L). The collagen hydrolysate obtained with optimum condition of production was then mixed with starch - a renewable source for polymeric material production - and glycerol - a byproduct of biodiesel production - to produce polymeric films by casting technique. Mechanical properties of four different compositions (with and without the presence of collagen hydrolysate and glycerol) of films were compared. The films produced with the addition of glycerol and collagen hydrolysate presented mechanical properties similar to the ones of commercial biodegradable films applied as mulches in agriculture. They also have in their composition a compound present in fertilizers - nitrogen - and possible traces of chromium, which is a micronutrient. Therefore, they can be an alternative to synthetic polymers.