Characterisation of adsorbent resins for the recovery of geldanamycin from fermentation broth

Abstract

Geldanamycin is a benzoquinone ansamycin, produced by the Actinomycete Streptomyces hygroscopicus var. geldanus, which possesses a broad spectrum antibiotic and anticancer activity. Adsorbent resins are gaining significant application in areas of product recovery, and in particular antibiotic recovery. It was decided to establish how effective such resins could be, for recovery of geldanamycin from fermentation broths, in a solid phase extraction. The extractions were batch adsorptions between the liquid phase fermentation broth, containing the geldanamycin and the solid phase adsorbent resins. The resins assessed were Amberlite XAD-4, 7, 16, 1180 and 1600, and Sepabeads SP-850 and Diaion HP-20. All resins assessed were capable of recovery of in excess of 90% of geldanamycin at a resin concentration of 15 g/l, although resins XAD-16, XAD-1600, XAD-1180 and Diaion HP-20 showed a higher capacity at lower resin concentrations than the others resins. All resins displayed a level of positive selectivity for adsorption of geldanamycin over that of contaminants. It was found that the rate of adsorption were dependant on temperature, where longer adsorption times were required at lower temperatures. The adsorbent resins displayed a wide pH range over which they were effective. The level of contaminant adsorption could be partially regulated through pH control. Inclusion of acetonitrile in the fermentation broth resulted in lower levels of geldanamycin adsorption, however for Diaion HP-20, at a mix of 80% fermentation broth, 20% acetonitrile, approximately 90% of the geldanamycin was adsorbed, but less than 10% of the contaminants present.