High-risk bio-waste processing by alkaline hydrolysis and isolation of amino acids

Abstract

Slaughterhouse waste can be very dangerous and potential risk for animal and human health. Brains and spinal cords are deemed high-risk substances and can be infected with prions ; their treatment is therefore only possible in strictly controlled conditions. One of the methods which can achieve the necessary reduction in health risk is alkaline hydrolysis. Standard alkaline hydrolysis is at 150°C, 3-6 hours, and 4 bars. In this investigations focus was on different alkaline conditions: temperature (135oC, 150oC, 153oC), time (2, 3, 6 hours), and base (NaOH and KOH) due to fact that amino acids are sensitive to variations on temperature, pressure and base media. Analyzed amino acid composition of hydrolyzed material at different testing conditions show successful hydrolysis. Highest value of protein, which is generally relatively low, was achieved with NaOH at a temperature of 135oC and time of 2 hours, whereas in the reaction with KOH the highest obtained value was achieved at 150oC and 3 hours. A dry substance increasing with time, and the highest value was achieved at the temperature of 150oC and time 6 hours for both bases (NaOH, and KOH). Most of the amino acids went full racemization during the process ; especially in D-amino acids like aspartic acid, glutamic acid, tryptophan and isoleucine. Lysine shows higher resistance to alkaline medium than other amino acids. Isolation of certain amino acids, like: asparagine, glutamic acid, glycine, alanine, and leucine, is possible because they show higher concentrations in hydrolysates.