Decoloring hemoglobin as a feedstock for second-generation bioplastics.

The color of red blood cell concentrate (RBCC) limits its application in human food, but there is potential to use it for second-generation bioplastics. Several methods have been developed to remove color from RBCC, but they are expensive or may produce difficult-to-remove toxic residues. Hydrogen peroxide treatment is a cheaper alternative. The effects of RBCC concentration, pH, and reaction temperature were the most important factors influencing the decolorizing process. They were investigated with the aim of developing a method that could be scaled to commercial level for producing a bioplastic feedstock. Initial trials showed pH was an important factor for decolorization and foaming. At pH 15 there was a 96% reduction in solution color and 8.4% solids were lost due to foaming. There was a 76% reduction in solution color at pH 2 and only 2.6% solids were lost due to foaming. The optimal reaction conditions were to centrifuge 9% w/w, pH 2 aqueous RBCC solution to remove aggregates. The solution was reacted at 30°C with 7.5 g of 30% (w/w) hydrogen peroxide. These conditions achieved a 93% reduction in solution color after 3 hr and the molecular weight of the decolored protein was not significantly reduced.