Extraction and assay of ferulic acid esterase from malted barley

Abstract

Ferulic acid esterase activity was detected in extracts of barley malt using an assay employing a novel artificial substrate, mono-feruloyl glycerol. Mono-feruloyl glycerol has been synthesized and analysed to determine its degree of substitution and purity. It consists of a mixture of the two isomers 1-feruloyl glycerol and 2-feruloyl glycerol. The extraction of ferulic acid esterase and its assay conditions have been optimised. The presence of both a detergent and reduced glutathione in the extraction medium increased the amount of enzyme extracted. A pH of 7.5 was optimal for enzyme activity. The enzyme in solution was only stable up to 30°C. The crude extract containing the enzyme released free ferulic acid from both soluble and insoluble cell wall materials. After extraction of the soluble enzyme, insoluble enzyme, capable of releasing free ferulic acid from feruloyl glycerol, was detected in the residual grain solids.