The production of feruloyl esterase activity by Bacillus spp. and lactobacilli can be detected in an agarplate assay. The assay involves the substitution of the main carbon source in specific agar with ethyl ferulate. A number of Bacillus spp., predominantly B. subtilis strains, were found to exhibit feruloyl esterase activity by this method. Of the examined lactobacilli, Lb. fermentum (NCFB 1751) showed the highest level of ferulic acid esterase activity. The enzyme was released from harvested cells by sonication and showed pH and temperature optima of 6.5 and 30 degrees C respectively.

Yeasts were isolated from unpasteurised apple juice on potato dextrose agar supplemented with tartaric acid and on malt extract agar containing chloramphenicol. Isolates were screened for feruloyl esterase and ferulic acid decarboxylase activities. Strains of Rhodotorula rubra, R minuta and Candida lambica produced both enzymes. Ferulic acid decarboxylase activity, resulting in the formation of the off‐flavour 4‐vinyl guaiacol, was highest for the C lambica isolate. This decarboxylase activity was associated with the washed resting cells. The crude enzyme showed temperature and pH optima of 35°C and 6.5, respectively. © 1999 Society of Chemical Industry