Enhanced production of nojirimycin via Streptomyces ficellus cultivation using marine broth and inhibitory activity of the culture for seeds of parasitic weeds

Root parasitic weeds, such as Orobanche spp. and Striga spp., cause serious damage to crops. Recently, it was demonstrated that nojirimycin (NJ) selectively inhibits seed germination in these weeds. In this study, we modified the medium for Streptomyces ficellus to increase its production of NJ and evaluated the culture as an antiparasitic weed agent. We screened alternatives to Pharmamedia™, an additive in the original medium, and found that marine broth stimulated NJ production. Moreover, soluble starch-depleted medium could maintain S. ficellus NJ production. The NJ concentration reached 710 mg/L after four-day batch culture in starch-depleted marine broth medium, which was 17-fold higher than that in the Pharmamedia™ medium. The culture in the marine broth medium inhibited seed germination of Orobanche spp. and Striga spp. as effectively as a standard solution of NJ.