Ultrafiltration for isolation and purification of oxytetracycline from industrial fermentation broth

The production of oxytetracycline (OTC) consists of acidification, filtration, decoloration and subsequent crystallization. Techniques for isolation and purification of OTC have remained largely unchanged for many years. The commonly used resin decoloration process is costly and has a lower production yield, which also generate a strong waste stream. In this work, an attempt was made to use ultrafiltration (UF) to replace conventional resin decoloring unit operation. UF membranes with molecular weight cut-off (MWCO) 4960.5u were employed. The experimental results show that UF is a promising alternative to resin absorption to obtain sufficiently pure OTC solution for crystallization. The recovery yield of OTC increases from 95.3% using resin adsorption to 98.6% with UF. When UF is combined with the pretreatment of OTC filtered broth by the flocculant K2Fe(CN)6-ZnSO 4, OTC crystallization yield would farther increase from 90.58% to 93.3% with an improved purity.