Sinigrin Degradation by Aspergillus sp. NR-4201 in Liquid Culture

A myrosinase-producing fungus, Aspergillus sp. NR-4201, was newly isolated from decayed mustard seed meal samples obtained in Lamphun, Thailand. When preincubated in a medium containing sinigrin, myrosinase was expressed intracellularly whereas none was detected in sinigrin-free medium. Sinigrin degradation was closely related to the presence of myrosinase. Induced mycelium consumed both glucose and sinigrin competitively, while non-induced myceliun exhausted glucose first and then sinigrin, with no myrosinase being produced during the glucose consumption period. The product allylcyanide was detected in incubation mixtures but its accumulation was delayed. Cell-free extracts incubated with sinigrin produced allylisothiocyanate at pH 5.6 and 7.2 but not at pH 4.0.