Applicability of adsorbent resins for the recovery of geldanamycin from streptomyces hygroscopicus var; geldanus fermentation broths

Abstract

Adsorbent resins are gaining increased application in recovery bioprocesses, thus it was decided to assess their applicability for the recovery of geldanamycin, an antibiotic produced Streptomyces hygroscopicus var. geldanus, in both a Downstream Processing (DSP) and In-Situ Product Recovery (ISPR) context. Antibiotic production was initially assessed using the conventional disk diffusion assay. This was inefficient for large sample sets, therefore a microtiter plate-based bioassay was developed. This assay was an improvement on the disk diffusion assay, it was high throughput, allowed quantitative assessment of sample bioactivity, but quantification of geldanamycin in fermentation samples, was not possible. To achieve this, a High Performance Liquid Chromatography (HPLC) method was developed. During method development, significant difficulties, including column fouling, low sample throughput and poor geldanamycin solubility and had to be addressed. Once these issues were resolved, the HPLC method could be used to treat large sample sets, with minimal column damage, and was therefore employed for analysis of all geldanamycin containing samples. Product recovery is key in bioprocesses, and it was found that the resins assessed had capacity and affinity for geldanamycin adsorption when applied in a DSP context. They were robust to temperature and pH changes and facilitated the generation of product streams of high product purity and concentration. Addition of solvent increase the selectivity of adsorption from fermentation broths, by approximately 5-fold. Two resins, Amberlite XAD-1600 and Diaion HP-20 were selected for further examination in an ISPR context based on their performance in DSP studies. Applied in an ISPR context, it was found that the resins were capable of adsorbing compounds other than geldanamycin and their inclusion impacted on the growth rate of the organism. An approximate 3-fold increase in production could be achieved depending on resin concentration and addition time. In summary adsorbent resins are suitable for recovery of geldanamycin from fermentation broth and their correct application can increase product yields