Study on utilizing solid food industry waste with brewers' spent grain and potato pulp as possible peroxidase sources

Abstract

This study found that extracts containing ionically bound proteins, isolated from potato pulp and brewers' spent grain, were characterized by high peroxidase activities. The kinetic parameters, namely Km and Vmax values, were typical for plant peroxidases. Seven peroxidase isoenzymes in potato pulp and two isoenzymes in brewers' spent grain were obtained from their respective ionically bound fractions. Peroxidases from both potato pulp and brewers' spent grain displayed high storage stability, over a 90-day-long storage period, if stored at −20°C with glycerol added to a concentration of 50% or as unsupplemented extracts at 4°C. Peroxidase activity was present in the covalently bound fraction of potato pulp, whereas it was absent in the respective fraction of brewers' spent grain. Covalently bound peroxidases from potato pulp displayed high activity, but low stability. Peroxidases extracted from brewers' spent grain and potato pulp, followed the ping-pong mechanism and the sequence mechanism, respectively. Practical applications Plant peroxidases are widely applicable in various fields of biotechnology and diagnostics. These enzymes are used for biosensor and glucometer construction and in conjugation with antibodies for the purpose of enzyme immunoassays. Using waste products as a peroxidase source provides a cost-friendly alternative to commercially available horseradish peroxidase and gives an opportunity to recycle waste from the food industry—processed plant biomass. Here, the properties of peroxidases from food waste products, namely potato pulp and brewers' spent grain are analyzed. The extracts were characterized by high storage stability and high enzymatic activity, which are two key traits necessary for the practical use of enzyme preparations.