Rapid detection of myrosinase-producing fungi: a plate method based on opaque barium sulphate formation

Abstract

A simple and rapid technique to assess the capability of fungi to produce myrosinase is reported. This was carried out by growing the tested fungi in sinigrin–barium agar plates. Strains capable of producing myrosinase were indicated by an opaque barium sulphate zone forming underneath and/or surrounding their colonies. This simple test has been confirmed by determination of myrosinase activity in liquid culture. In positive isolates, enzyme acitivity was detected in cell-free extracts, not in culture filtrates. In the case of non-myrosinase-producing strains, no opaque zone was observed and the enzyme was not detected either in cell-free extracts or in culture filtrates.