Protein recovery from bioethanol stillage by liquid hot water treatment

Abstract

Protein recovery from biogenic residues offers a high potential for increasing the added value. This paper investigates the protein recovery from bioethanol stillage by liquid hot water treatment at pH 3–11 and 110–210 °C for 10–90 min. The results show that protein solubilization starts at 89 °C and is limited by temperature. However, all amino acids except glutamic acid start to degrade at 170 °C. Especially lysine, arginine and asparagine undergo Maillard reactions, whereby degradation is favoured by bases; acids show a stabilizing effect. The highest protein yield in the hydrolysate is 75% with a concentration of 53%-DM at 170 °C and 20 min. In addition, kinetic modelling of the rate constants for protein solubilization and amino acid degradation is performed. Rate constants for amino acid degradation are about one order of magnitude higher for polar than for non-polar amino acids.